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| 1585 | Computer 121
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3D Balanced Steady-State Free Precession (bSSFP) Imaging on an Ultra-Low-Field 0.055T MRI System |
| Ye Ding1,2, Shi Su1,2, Linfang Xiao1,2, Yujiao Zhao1,2, Jiahao Hu1,2, Junhao Zhang1,2, Vick Lau1,2, Christopher Man1,2, Alex T.L. Leong1,2, and Ed X. Wu1,2 | ||
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, China, 2Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China |
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Keywords: Low-Field MRI, Body Recently, there has been an impetus to develop ultra-low-field (ULF) MRI technologies, which present opportunities for low-cost and portable imaging in point-of-care scenarios. Balanced steady-state free precession (bSSFP) is a time-efficient imaging sequence yet its feasibility at ULF remains unexplored. In this study, we implemented bSSFP sequence at 0.055T, and successfully demonstrated phantom, brain and extremity imaging. |
| 1586 | Computer 122
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Magnetization Transfer Imaging using non-balanced SSFP at Ultra-Low Field |
| Sharada Balaji1, Adam Dvorak1, Francesco Padormo2, Rui Pedro A.G Teixeira2, Megan E. Poorman2, Alex L. MacKay1,3, Tobias C. Wood4, Steven C.R. Williams4, Sean C.L. Deoni5, Shannon H. Kolind1,3,6, and Emil Ljungberg4,7 | ||
1Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, 2Hyperfine Inc, Guilford, CT, United States, 3Radiology, University of British Columbia, Vancouver, BC, Canada, 4Neuroimaging, King's College London, London, United Kingdom, 5MNCH D&T, Bill and Melinda Gates Foundation, Seattle, WA, United States, 6Medicine, University of British Columbia, Vancouver, BC, Canada, 7Medical Radiation Physics, Lund University, Lund, Sweden |
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Keywords: Low-Field MRI, Magnetization transfer We have demonstrated a method for introducing Magnetization Transfer (MT) weighting in a non-balanced SSFP sequence (PSIF) at 64mT by changing the total power of the on-resonance RF excitation pulse. The presence of the MT effect was validated through simulations, experiments in phantoms of water, cream, and hair conditioner, as well as in-vivo. Changes to the signal amplitude in the conditioner from the flip angle and pulse width of the RF pulse illustrated the presence of MT saturation. An example protocol with MT weighting was applied in-vivo to generate magnetisation transfer ratio maps. |
| 1587 | Computer 123
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Balanced steady-state free precession imaging and associated rapid relaxation time mapping on a point-of-care 46 mT Halbach MRI scanner |
| Chloé Najac1, Florian Birk2,3, Tom O’Reilly1, Klaus Scheffler2,3, Andrew Webb1, and Rahel Heule2,3,4 | ||
1C.J. Gorter MRI Center, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, 2Department of High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 3Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany, 4Center for MR Research, University Children's Hospital, Zurich, Switzerland |
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Keywords: Low-Field MRI, Data Acquisition Point-of-care imaging with low-field MRI (<0.1T) is a potential game changer for low-income countries and the intensive care unit. The main challenge is the low SNR. Balanced steady-state free precession (bSSFP) sequences are fast and SNR-efficient. However, bSSFP is very sensitive to B0 inhomogeneities resulting in banding artifacts. We evaluated the feasibility of using bSSFP on our 46 mT MRI scanner. By acquiring 17 bSSFP datasets with linearly increasing frequency offsets (from 0 to 1/TR), we could reconstruct banding-free maximum-intensity images as well as F0 and F-1 SSFP configurations, which we employed for rapid relaxation time mapping. |
| 1588 | Computer 124
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On the estimation of age-related volumetric brain changes using ultra-low-field MR images |
| Peter Hsu1, Daniel K. Sodickson1,2, Hersh Chandarana1, Justin Fogarty1, Patricia Johnson1,2, and Jelle Veraart1,2 | ||
1Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States, 2Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States |
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Keywords: Low-Field MRI, Brain, ultra-low-field MRI, point-of-care MRI The high cost of clinical MRI has severely limited its accessibility in many regions. Ultra-low-field (ULF) MRI systems have been developed to address this issue, providing diagnostic imaging at a significantly lower cost. However, computational tools that are used for clinical scans are often not applicable to ULF images which suffer from both SNR and resolution loss. Here, we compare two approaches for improving the resolution of ULF images and two techniques for extracting volumetric information from each approach. We show that given effective post-processing, ULF images can capture expected age-related volumetric changes in the brain. |
| 1589 | Computer 125
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Optimized Extremity Coil System for Gradient-Free Low-Field MRI using the Bloch-Siegert Shift for RF Spatial Encoding |
| Sai Abitha Srinivas1, Christopher E Vaughn1, Jonathan B Martin 1, and William A Grissom1 | ||
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States |
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Keywords: Low-Field MRI, Low-Field MRI Traditional B0 gradients have several drawbacks including high acoustic noise, PNS, bulkiness, and high cost. To address this, we present a coil system for Bloch-Siegert (BS) RF encoding comprising an optimized square root solenoid with a bucking coil for high efficiency encoding and a nested uniform saddle coil for the imaging Tx/Rx coil at 47.5mT (2MHz), a field strength that is especially attractive due to its low SAR and accessibility. The coil designed for in-vivo imaging was evaluated in simulation including SAR measurements and experimentally on a resolution phantom using a 3D BS phase-encoded imaging and optimized ‘U’ shaped pulses. |
| 1590 | Computer 126
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Overhauser-enhanced MRI at ultra-low fields: a new system for imaging of free radicals in rodents |
| Dahmane Boudries1, Philippe Massot1, Elodie Parzy1, Seda Seren1, Philippe Mellet2, Jean-Michel Franconi1, Sylvain Marque3, Florian Fidler4, Stefan Wintzheimer5, Markus Mützel5, and Eric Thiaudiere1 | ||
1CNRS, Bordeaux, France, 2INSERM, Bordeaux, France, 3CNRS, Marseille, France, 4Fraunhofer, Würzburg, Germany, 5Pure devices, Rimpar, Germany |
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Keywords: Low-Field MRI, Molecular Imaging, Ultra low field, OMRI, DNP, Magnetic prepolarization A new MRI system at Ultra-low field (206 µT) was designed for Overhauser-enhanced MRI. It allows both conventional MRI with pre-polarization at 20 mT and Dynamic Nuclear Polarization in the 70MHz range in living rats. Anatomical images in 3D allowed a correct visualization of the rat body shape. OMRI with injected or instilled stable and non-toxic nitroxides permitted to detect the free radicals in the lungs, the kidneys and the bladder. The work opens the way of molecular imaging of abnormal proteolysis in the context of a variety of diseases in large animals. |
| 1591 | Computer 127
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Magnetic Resonance Elastography at 0.055 Tesla: A Preliminary Study |
| Shi Su1,2, Ye Ding1,2, Jiahao Hu1,2, Vick Lau1,2, Yujiao Zhao1,2, Junhao Zhang1,2, Christopher Man1,2, Alex T.L. Leong1,2, and Ed X. Wu1,2 | ||
1Laboratory of Biomedical Imaging and Signal Processing, the University of Hong Kong, Hong Kong, China, 2Department of Electrical and Electronic Engineering, the University of Hong Kong, Hong Kong, China |
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Keywords: Low-Field MRI, Elastography Recent development of ultra-low-field (ULF) MRI presents opportunities for low-cost and portable imaging in point-of-care scenarios or/and low- and mid-income countries. Magnetic resonance elastography (MRE) is an essential part of MR abdominal imaging especially for chronic liver diseases. In this study, we explore the MRE at 0.055 Tesla. We demonstrate the feasibility of MRE based on phantom experiments at 0.055 Tesla. |
| 1592 | Computer 128
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Portable MRI for major sporting events – a case study on the MotoGP World Championship |
| Teresa Guallart-Naval1,2, José Miguel Algarín2,3, Rubén Bosch1, Francisco Juan-Lloris4, Eduardo Pallás2,3, Juan Pablo Rigla1, Pablo Martínez4, José Borreguero1, José María Benlloch2,3, Fernando Galve2,3, and Joseba Alonso2,3 | ||
1Tesoro Imaging SL, Valencia, Spain, 2Institute for Instrumentation in Molecular Imaging (i3M), Universitat Politècnica de València, Valencia, Spain, 3Institute for Instrumentation in Molecular Imaging (i3M), CSIC, Valencia, Spain, 4Physio MRI SL, Valencia, Spain |
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Keywords: Low-Field MRI, Low-Field MRI, Portable MRI, Sport event MRI Here we study the potential MR value of a low-field portable system for use in major sporting events, specifically in the Motorcycle Grand Prix held in Valencia (Spain) between November 3rd and 6th, 2022. The system was transported in a small truck, installed in the main surgery room of the circuit medical facilities, and operational around 30 minutes after arrival. Overall, 15 subjects were scanned in four days, with a total of 21 extremity acquisitions. This work demonstrates that portable MRI machines can aid the diagnostic capabilities of medical staff in sporting events and competitions. |
| 1593 | Computer 129
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Accelerated imaging of resected lymph nodes at high spatial resolution using a portable low-field MRI scanner |
| Arthur de Lange1, Lejla Alić1, Bennie ten Haken1, and Frank F.J. Simonis1 | ||
1TechMed Centre, University of Twente, Enschede, Netherlands |
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Keywords: Low-Field MRI, New Devices After sentinel lymph nodes are detected using SPIONs and excised, their characterization is important to detect possible metastases. In this research a low-field (0.5T) tabletop MRI scanner was tested for this purpose using 4x accelerated high resolution 3D acquisition. Both simulations and experiments on excised pig lymph nodes showed promising results, with the accelerated scans showing similar image quality with respect to fully sampled datasets. This protocol shows lymph nodes can be imaged at 0.25 mm isotropic resolution within reasonable scan times. Clinical usage should be proven by scanning true metastatic lymph nodes. |
| 1594 | Computer 130
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Relaxation Times of the Musculoskeletal Tissues at 0.55 T |
| Iman Khodarahmi1, Mary Bruno1, Ryan Brown1, Jan Fritz1, and Mahesh B Keerthivasan2 | ||
1NYU Langone School of Medicine, New York, NY, United States, 2Siemens Medical Solutions USA Inc., Malvern, PA, United States |
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Keywords: Joints, MSK Modern 0.55 T MRI promises to increase worldwide healthcare access through lower costs. Knowledge of the tissue relaxation parameters is essential to achieve the desired image contrast. Here for the first time, we quantify the T1 and T2 relaxation times of the musculoskeletal tissues through a Bloch model-based fitting approach. Our results show that the T1 relaxation time of non-fluid tissues is about 47% of those at 1.5 T. T2 relaxation times are about 70% of that of 1.5 T for synovial fluid, bone marrow and subcutaneous fat, and approximately similar to that of 1.5 T for cartilage and muscle. |
| 1595 | Computer 131
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Point-of-Care Knee MRI at 0.064T: Expanded Evaluation and Initial Comparison with Clinical Knee MRI at 3T |
| Jennifer M Watchmaker1, Ding Xia2, Idoia Corcuera-Solano1, Etan Dayan1, Justin Ngeow1, Fang Liu3, Zahi Fayad2, Mingqian Huang1, and Li Feng2 | ||
1Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States, 2Biomedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, 3Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Boston, MA, United States |
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Keywords: Tendon/Ligament, Low-Field MRI, knee, hardware At last year’s ISMRM, a pioneering work was presented to demonstrate the initial feasibility and performance of point-of-care knee MRI at 0.064T using a Hyperfine Swoop portable MRI scanner. This work extended that study for further evaluation in an expanded cohort of healthy subjects and subjects with knee pathology, and compare low-field imaging with clinical 3 Tesla imaging in a subset of volunteers. |
| 1596 | Computer 132
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Multi-reader evaluation of real-time MRI of the actively moving wrist at 0.55 Tesla |
| Abhijit J Chaudhari1, Robert D Boutin2, Yongwan Lim3, Sophia Cui4, Robert M Szabo5, and Krishna S Nayak3 | ||
1Radiology, University of California Davis, Sacramento, CA, United States, 2Radiology, Stanford University, Palo Alto, CA, United States, 3University of Southern California, Los Angeles, CA, United States, 4Siemens Medical Solutions, Malvern, PA, United States, 5Orthopaedic Surgery, University of California Davis, Sacramento, CA, United States |
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Keywords: Joints, Skeletal, Real-time imaging; Wrist Kinematics; Dynamic imaging. We acquired real-time MRI of the actively moving wrist in humans utilizing a high-performance 0.55T system. Resulting images and associated static wrist scans were assessed by two expert readers blinded to acquisition parameters. Our results show that images acquired at a high temporal resolution of 12.6 ms per frame demonstrate minimal image degradation compared to images acquired at temporal resolution of 100 ms or higher, and enable improved characterization of wrist motion. These benefits support further studies to assess high-performance 0.55T systems for the evaluation of dynamic dysfunction of the wrist. |
| 1597 | Computer 133
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High-performance, Shielding-free MSK Imaging at 100mT Enabled by Retrospective Active EMI Cancellation |
| Mauro Spreiter1, Reina Ayde1,2, Necati Ozcakal1, Tobias Senft1, Najat Salameh1,2, and Mathieu Sarracanie1,2 | ||
1Center for Adaptable MRI Technology (AMT Center), Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland, 2AMT Center, Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Aberdeen, United Kingdom |
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Keywords: Low-Field MRI, Low-Field MRI Electromagnetic interference cancellation method EDITER is implemented in an unshielded low-field MRI scanner at 100mT by addition of only two EMI detection coils to the acquisition chain. The method’s effectiveness is illustrated in high resolution MSK images of healthy volunteer’s hands. Full 3D images with sub-millimeter in-plane or isotropic millimeter voxel dimensions can be obtained in clinically acceptable acquisition times. This approach, in combination with acceleration strategies, opens perspectives in MSK imaging in the field with portable scanners and/or in low resource environments. |
| 1598 | Computer 134
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Bringing MRI to Low- and Middle- Income Countries: Directions, Challenges and Potential Solutions |
| Sola Adeleke1, Sanjana Murali2, Hao Ding2, Fope Adedeji3, Cathy Qin4, Johnes Obungoloch5, Tamir Sirkis6, Iris Asllani7, Ntobeko Ntusi8, Regina Mammen9, Udunna Anazodo10, and Thoralf Niendorf11 | ||
1School of Biomedical engineering and imaging sciences, King's College London, London, United Kingdom, 2School of Medicine, Imperial College London, London, United Kingdom, 3School of Medicine, University College London, London, United Kingdom, 4Department of Radiology, Imperial College Healthcare Trust, London, United Kingdom, 5Department of Biomedical Engineering, Mbara University of Science and Technology, Mbara, Uganda, 6Royal Berkshire NHS Foundation Trust, Reading, United Kingdom, 7Department of Biomedical Engineering, Rochester Institute of Technology, New York, NY, United States, 8Department of Medicine, University of Cape Town and Groote Schuur Hospital, Cape Town, South Africa, 9Department of Cardiology, Essex Cardiothoracic Centre, Chelmsford, United Kingdom, 10Montreal Neurological Institute, McGill University, Montreal, QC, Canada, 11Berlin Ultrahigh Field Facility, Berlin, Germany |
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Keywords: Low-Field MRI, MR Value, Accessible MRI; Affordable MRI; Sustainable MRI While innovations in MRI technology continue to advance healthcare in the global north, there is a persistent disparity in MRI access and research opportunities in low- and middle-income countries (LMICs). Reasons for this longstanding disparity include technological, economic, geopolitical, and social factors. As awareness of the situation expands, concerted efforts are underway to address it by developing sustainable approaches designed with and for local communities. Here, we provide a framework of such approaches by tackling different aspects of MRI development and access in LMICs. |
| 1599
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Computer 135
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Low-field MR Multitasking for an integrated abdominal MRgRT imaging framework |
| Junzhou Chen1,2, Ye Tian3, Namgyun Lee3, Mingsong Cao4, Wensha Yang5, Sophia Cui6, Krishna Nayak3, Debiao Li2,7, Anthony Christodoulou2,7, and Zhaoyang Fan1,5 | ||
1Radiology, University of Southern California, Los Angeles, CA, United States, 2Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States, 3Electrical Engineering, University of Southern California, Los Angeles, CA, United States, 4University of California, Los Angeles, Los Angeles, CA, United States, 5Radiation Oncology, University of Southern California, Los Angeles, CA, United States, 6Siemens Medical Solutions, Los Angeles, CA, United States, 7Cedars-Sinai Medical Center, Los Angeles, CA, United States |
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Keywords: Low-Field MRI, Radiotherapy MR applications in radiation therapy has shown great promise for highly conformal treatment. However, MRgRT in the abdomen remains challenging due to motion and the sheer number of organs. In this work, we have demonstrated at 0.55T an integrated multi-task MR platform for adaptive radiation planning and treatment monitoring in the abdomen. We propose using a hybrid GRE-TSE sequence, from a single "pre-beam" scan we are able to generate a volumetric, multi-contrast and motion resolved images for adaptive treatment planning as well as enabling multi-contrast 3D real-time display during treatment. |
| 1600 | Computer 136
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Simultaneous multi-slice real-time cardiac MRI at 0.55T |
| Ecrin Yagiz1, Parveen Garg2, Krishna S. Nayak1, and Ye Tian1 | ||
1Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, 2Division of Cardiology, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States |
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Keywords: Low-Field MRI, Low-Field MRI A standard cine MRI exam typically collects a stack of short-axis slices to cover all left ventricular myocardium and uses electrocardiogram gating and breath-holds. Real-time imaging methods are often used to resolve issues with insufficient gating signal or breath-hold failure. In this work, we demonstrate that real-time SMS cardiac imaging at 0.55T provides sufficient blood-myocardium contrast and regional wall motion evaluation with three-fold acceleration compared to real-time single-band and Cartesian breath-hold ECG-gated cine. We also show an alternative reconstruction approach, clustered locally low rank that can improve image quality. |
| 1601 | Computer 137
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On the frequency dependence of electrical conductivity |
| Ulrich Katscher1 and Peter Vernickel1 | ||
1Philips Research Europe, Hamburg, Germany |
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Keywords: Low-Field MRI, Electromagnetic Tissue Properties Electric conductivity depends on the frequency of the probing electric field. The impact of the frequency differs between human tissue types, e.g., it is lower for body fluids than for cellular tissue types. The upcoming mid-field systems suggest to investigate this frequency dependence with MRI. This study investigated two phantoms, with and without cellular structure, to explore the frequency dependence of conductivity using “Electrical Properties Tomography”. The conductivity results obtained at three different Larmor frequencies were used to estimate the conductivity at lower frequencies in the range of kHz as required for, e.g., EEG source localization. |
| 1602 | Computer 138
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Optimized MR Fingerprinting OPTIMUM in vivo in the vicinity of a metallic implant at low field |
| Gabriel Zihlmann1,2, Mathieu Sarracanie1,2, and Najat Salameh1,2 | ||
1Center for Adaptable MRI Technology (AMT center), Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland, 2AMT center, Institute of Medical Sciences, school of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Aberdeen, United Kingdom |
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Keywords: Low-Field MRI, MR Fingerprinting Magnetic susceptibility changes at interfaces induce artefacts, and hence compromises MRI diagnostic value. Low-Field (LF) MRI is inherently less sensitive to susceptibility artifacts making it suitable for imaging near metallic implants. In addition, the dispersion in T1-contrast is enhanced at LF. To evaluate the potential for new contrast mechanisms, quantitative imaging would be key if acquisition times are compatible with clinical constraints. In that context, model-based multi-parametric OPTIMUM was performed in a healthy volunteer’s forearm carrying a titanium plate from plate-osteosynthesis surgery. Performance of two signal models, one oblivious to intravoxel dephasing and the other accounting for it was compared. |
| 1603 | Computer 139
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Outer Volume Saturation using Adiabatic Inversion Pulses in an Inhomogeneous Transmit Field |
| Muller De Matos Gomes1, Sourajit Mustafi1, Meredith Sadinski1, Kartiga Selvaganesan2, and Aleksandar Nacev1 | ||
1Promaxo, Oakland, CA, United States, 2Yale School of Engineering & Applied Science, Yale, New Haven, CT, United States |
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Keywords: RF Pulse Design & Fields, Low-Field MRI A method for saturating the outer volume in a single sided low field MRI scanner has been developed. By saturating the outer volume using this method, magnetization from regions where the gradient fields are highly nonlinear may be removed from the image, resulting in less image artifacts. |
| 1760 | Computer 121
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A SNR and contrast comparison study at 0.11T, 0.25T, 1.5T and 3T MRI systems |
| Yueqi Qiu1, Haoran Bai1, Hao Chen1, and Zhiyong Zhang1 | ||
1School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai Jiao Tong University, Shanghai, China |
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Keywords: Low-Field MRI, Low-Field MRI Low-field MRI systems have seen a renaissance recently due to improvements in technology and its low costs. However, properties like SNR, T1 and T2 values of low fields have caused a lot of concern because they always change with field strengths. This study conducted the SNR comparison based on phantom and fitted the quantitative mapping of human brains at 0.11T, 0.25T, 1.5T and 3T to design a set of protocols enabling similar contrasts of the typical clinical images at different fields. The impacts of lowered magnetic field strengths on imaging quality were shown in this study. |
| 1761 | Computer 122
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Stop-Motion RF for Improving Spatial Resolution in Non-Linear Gradient-Free Low-Field MRI |
| Anja Samardzija1, Kartiga Selvaganesan1, Younghyun Ha2, Zhehong Zhang1, Chenhao Sun2, Heng Sun1, Gigi Galiana2, and Todd Constable2 | ||
1Biomedical Engineering, Yale University, New Haven, CT, United States, 2Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States |
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Keywords: Low-Field MRI, RF Arrays & Systems We developed a stop-motion imaging technique in which a 3x3 radiofrequency coil that transmits Bloch-Siegert encodings is placed in a different position within the field-of-view for each MR signal acquisition. This study is performed using a non-linear gradient-free low-field MRI system. High spatial resolution is achieved through stop-motion imaging. We show that stop-motion imaging done with a total of 200 encodings (20 imaging positions and 10 encodings per position) outperformed stationary imaging performed with 200 encodings (1 imaging position and 200 encodings per position). |
| 1762 | Computer 123
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Widened-bandwidth RF volume coil using crossed elliptical winding for Halbach-array-based portable MRI knee scanner |
| MEENA RAJENDRAN1 and SHAOYING HUANG1 | ||
1Engineering Product Developement, Singapore University of Technology and Design, Singapore, Singapore |
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Keywords: Low-Field MRI, Low-Field MRI, RF coil A widened-bandwidth RF volume coil using crossed elliptical winding pattern (symmetric in azimuthal direction) is proposed for Halbach-array-based portable MRI knee scanner. The fractional bandwidth (FBW) is 0.51% centered at 2.84 MHz (B0 = 67mT) with a high B1 field strength (57µT) and a high homogeneity (94%) within a cylindrical volume of diameter and length of both 95mm. Compared to solenoid coils of comparable dimensions, it is an increase of 18% in FBW, an improvement in homogeneity by 6.1%, and only a compromise of 1.9% in the field strength, which is the best combination. |
| 1763 | Computer 124
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Abdominal MRI at 0.55 T: Initial evaluation and optimization in healthy subjects |
| Anupama Ramachandran1, Hero Hussain1, Mishal Mendiratta Lala2, Jacob Richardson3, Nancy Dudek2, Joel Morehouse2, Katherine Wright4, Vikas Gulani3, and Nicole Seiberlich3 | ||
1Radiology, University of Michigan, Ann Arbor, MI, United States, 2University of michigan, Ann arbor, MI, United States, 3Radiology, University of michigan, Ann arbor, MI, United States, 4University of Michigan, Ann arbor, MI, United States |
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Keywords: Low-Field MRI, Body, Abdomen Abdominal MRI including MRCP was performed in 15 healthy subjects on both a 0.55T and a 1.5T MR system. Image quality (IQ) was rated by two radiologists (22 and 17 yrs experience). All sequences were rated acceptable at 0.55T. In comparison to 1.5T, IQ scores at 0.55T were higher for DWI and 3D MRCP, and lower for the other sequences. Acquisition times were longer at 0.55T for all sequences except 3D MRCP. Thus, acceptable quality abdominal images can be obtained on a commercial 0.55T system with slightly lower IQ ratings of some of the sequences compared to 1.5T. |
| 1764 | Computer 125
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Denoising Simulated Low-Field MRI (70mT) using Denoising AutoEncoders (DAE) and Cycle-Consistent Generative Adversarial Network (Cycle-GAN) |
| Fernando Vega1,2,3, Abdoljalil Addeh1,2,3, and M. Ethan MacDonald1,2,3,4 | ||
1Biomedical Engineering, University of Calgary, Calgary, AB, Canada, 2Electrical & Software Engineering, University of Calgary, Calgary, AB, Canada, 3Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, 4Department of Radiology, University of Calgary, Calgary, AB, Canada |
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Keywords: Low-Field MRI, Machine Learning/Artificial Intelligence, MRI, Unpaired Image Translation In this work, a denoising Cycle-GAN is implemented to yield high-field, high resolution, high signal-to-noise ratio MRI images from simulated low-field, low resolution, low signal-to-noise MRI images. Resampling and additive Rician noise were used to simulate low-field MRI. Images were utilized to train a DAE and Cycle-GAN, with paired and unpaired cases, respectively. Both networks were evaluated using SSIM and PSNR image quality metrics. This work demonstrates the use of advanced machine learning to improve low-field MRI images that can outperform classical denoising autoencoders and does not require image pairs. |
| 1765 | Computer 126
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Muscle volumetry from low-field scans and its relation to performance in physical activities |
| José Miguel Algarín1,2, Teresa Guallart-Naval2,3, Ana Ferri-Caruana4, Rubén Bosch3, Francisco Juan-Lloris5, Eduardo Pallás1,2, Juan Pablo Rigla3, Pablo Martínez5, José Borreguero3, José María Benlloch1,2, Fernando Galve1,2, and Joseba Alonso1,2 | ||
1Institute for Instrumentation in Molecular Imaging (i3M), CSIC, Valencia, Spain, 2Institute for Instrumentation in Molecular Imaging (i3M), Universitat Politècnica de València, Valencia, Spain, 3Tesoro Imaging SL, Valencia, Spain, 4Educación Física y Deportiva, Universitàt de València, Valencia, Spain, 5Physio MRI SL, Valencia, Spain |
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Keywords: Low-Field MRI, Low-Field MRI, Sport MRI Here we show the results of the first systematic study performed in our low-field 72 mT MRI scanner. Calf images were acquired from 35 volunteers whose performance was measured during different physical activities before the scan. We segmented the images to determine the cross-sectional area and volume of the gastrocnemius muscles and correlated the results with the muscular activity measurements of the volunteers. We found that the medial gastrocnemius muscle volume correlates significantly with participants weight and unilateral jump capacity. |
| 1766 | Computer 127
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Feasibility of integrating a wearable accelerometer in very low-field MRI to detect motion |
| Keerthi Sravan Ravi1,2, Kunal Aggarwal3, John Thomas Vaughan Jr.2, Yun Soung Kim4, and Sairam Geethanath5 | ||
1Biomedical Engineering, Columbia University, New York, NY, United States, 2Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States, 3Accessible MR Lab, BMEII, Diagnostic, molecular and interventional radiology, Icahn School of Medicine at Mt. Sinai, New York City, NY, United States, 4Biomedical Engineering and Imaging Institute, Dept. of Diagnostic, Molecular and Interventional Radiology,, Mt.Sinai, New York, NY, United States, 5Accessible MR Laboratory, Biomedical Engineering and Imaging Institute, Dept. of Diagnostic, Molecular and Interventional Radiology,, Mt. Sinai, New York, NY, United States |
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Keywords: Low-Field MRI, Low-Field MRI These artifacts degrade image quality, often causing misdiagnosis. A 6-axis motion tracking sensor (ICM-20649, TDK-InvenSense) with a full-scale range of +-4000 degrees per second for the gyroscope and +-30g for the accelerometer was integrated with a 50mT scanner. The sensor’s readings can successfully be processed to detect motion. However, it resulted in zipper artifacts and degraded image quality in a phantom experiment. Still, the sensor’s placement on the forehead or the temples or the chin might not significantly impact brain data when coupled with slab-wise shimming. |
| 1767 | Computer 128
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Optimization of the magnetization-prepared rapid gradient echo (MP-RAGE) sequence for 0.55 T |
| Jessica Schäper1,2 and Oliver Bieri1,2 | ||
1Department of Biomedical Engineering, University of Basel, Basel, Switzerland, 2Division of Radiological Physics, Department of Radiology, University Hospital Basel, Basel, Switzerland |
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Keywords: Low-Field MRI, Brain, MP-RAGE, low-field, white matter, gray matter The MP-RAGE is the most commonly used sequence for structural brain imaging in clinical routine. Consequently, the optimization of imaging parameters for maximum contrast and signal is an important task. In this work, we implemented a previously developed computation and calculated optimal parameters for 0.55T. Additionally, the obtained images were compared with a gray-white matter contrast-optimized FLASH. Computing the contrast-to-noise ratio revealed a clear benefit for MP-RAGE over FLASH at mid to low resolutions, while a trend towards similar or even higher contrast-to-noise ratios for FLASH as compared to MP-RAGE at high resolutions was observed. |
| 1768 | Computer 129
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An initial exploration of spiral imaging for quantitative fetal T2* mapping on a low-cost low-field MRI scanner |
| Jordina Aviles Verdera1,2, David Leitao1,2, Daniel West1,2, Joseph V Hajnal 1,2, Shaihan Malik1,2, Raphael Tomi-Tricot1,2,3, and Jana Hutter1,2 | ||
1Center for the Developing Brain, School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom, 2Biomedical Engineering Department, School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom, 3MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom |
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Keywords: Low-Field MRI, Data Acquisition Fetal MRI is an important complementary technique to ultrasound to monitor fetal health. Low-field MRI benefits from reduced distortion, increased B1 homogeneity, wider bore sizes for maintained field homogeneity and longer T2*. The latter is particularly beneficial for single-shot techniques as it allows more flexible and longer read-out strategies. This abstract explores, for the first time, spiral read-out for fetal brain T2* relaxometry and offers preliminary quantitative fetal brain T2* results. Next steps include further exploration of flexible read-out strategies such as undersampled interleaved spirals to work towards higher temporal resolution and motion robustness. |
| 1769 | Computer 130
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General implementation of frequency–space reconstruction |
| Marko Havu1, Koos Zevenhoven1, Antti Mäkinen1, and Risto J Ilmoniemi1 | ||
1Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland |
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Keywords: Low-Field MRI, Image Reconstruction In low-field and ultra-low-field MRI, concomitant fields can cause severe blurring and distortion in traditional Fourier reconstruction. We have developed an improved image reconstruction framework based on our previously published method that uses a frequency–space formulation. It provides more accurate reconstruction results with the cost of increased computation time. Known inhomogeneity and other field nonidealities can be incorporated into the model to improve the quality of the reconstruction. The framework will be published as open source. |
| 1770 | Computer 131
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Characterization of Concomitant Gradient Fields and their effects on a 46 mT Halbach-Based point-of-care MRI system |
| Bart de Vos1, Rob Remis2, and Andrew Webb1,2 | ||
1C.J. Gorter MRI Center, Leiden University Medical Center, Leiden, Netherlands, 2Circuits and Systems, Delft University of Technology, Delft, Netherlands |
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Keywords: Low-Field MRI, Artifacts, Concomitant fields Low field Halbach systems are susceptible to concomitant gradient effects. The associated fields are significantly different from clinical systems and are presented here for the first time. The corresponding equations and associated effects are verified using a spin echo sequence on a 46 mT Halbach system where a gradient strength of 10 mT/m on a phantom with maximum dimension of 200 mm is observed to create distortions. These are most evident in the transverse plane, where the phase encoding gradient causes blurring and overlapping the other transverse gradient lobe results in an additional warping effect. |
| 1771 | Computer 132
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Study of Frequency selective surface (FSS) to shield solenoids for low-field portable MRI |
| MEENA RAJENDRAN1 and SHAOYING HUANG1 | ||
1Engineering Product Developement, Singapore University of Technology and Design, Singapore, Singapore |
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Keywords: Low-Field MRI, Low-Field MRI The lightweight frequency selective surface(FSS) using high-pass inductive mesh grids is proposed as shielding of RF solenoids at 2.84MHz for an MRI system using a Halbach array(average B0=67mT). Its effects on the coil B1-sensitivity and the shielding effectiveness are examined. A solenoid(diameter=60mm) was used as an example and the shielding of 5-25mm away was examined. The 5mm-away-FSS-shielded coil has 50.1% (in simulation) and 91.3% (in measurements) higher B1-sensitivity and comparable shielding effectiveness within a defined FoV compared to the copper-shielded coil of the same dimensions. The measured data agree with the simulated ones. |
| 1772 | Computer 133
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Breast and Chest RF Design and Optimization for Ultra-low Field MRI |
| Torben P.P Hornung1,2,3, Neha Koonjoo1,2, Susu Yan3,4, Matthew S Rosen1,2,5, and Thomas R Bortfeld3,4 | ||
1Department of Radiology, A.A Martinos Center for Biomedical Imaging / MGH, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Department of Physics, ETH Zürich, Zürich, Switzerland, 4Department of Radiation Oncology, MGH, Boston, MA, United States, 5Department of Physics, Harvard University, Cambridge, MA, United States |
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Keywords: Low-Field MRI, Breast, Hybrid & Novel System Technology MRI guidance in Proton Therapy can improve breast cancer targeting accuracy during treatment planning. This study focuses on RF coil optimization for breast imaging at ultra-low field where proton beam deflection is minimal. Our previous optimization algorithm was further improved to adapt to any breast-shaped coil and any anatomical region. It was also developed for organs-at-risk imaging with a deep view into the chest. This new optimization method was tested for a single-channel conical-shaped coil and validated with imaging. The optimized coil showed a more homogenous B-field compared to its unoptimized evenly spaced wound coil in agreement with the simulations. |
| 1773 | Computer 134
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Improved T1w Imaging at Ultra-Low Field by use of phase-sensitive reconstruction |
| Samson Lecurieux Lafayette1, Francesco Padormo2, Paul Cawley1, Emil Ljunberg3,4, Rui Teixeira2, David Edwards1, Mary Rutherford1, Tomoki Arichi1, and Joseph Hajnal1 | ||
1Perinatal Imaging & Health, King's College, London, United Kingdom, 2Hyperfine, London, United Kingdom, 3Department of Neuroimaging, King's College, London, United Kingdom, 4Department of Medical Radiation Physics, Lund University, Lund, Sweden |
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Keywords: Low-Field MRI, Brain A phase-sensitive reconstruction is used on adult and neonatal T1w acquisitions on a ultra-low field point-of-care MRI system. We show improved image contrast and reduction in confusing intensities associated with rectification of negative signals. |
| 1774 | Computer 135
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Gradient non-linearity estimation in an Open MRI scanner |
| Olivier E Mougin1, Paul Glover1, Richard Bowtell1, and Penny A Gowland1 | ||
1SPMIC, University of Nottingham, Nottingham, United Kingdom |
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Keywords: Low-Field MRI, Gradients Open magnet provide advantageous facility for imaging the human body in a natural way. However field inhomogeneities can reduce the utilisable imaging field-of-view. We present a simple way to map the static field inhomogeneity and the non-linear gradient inhomogeneity in order to correct them during the image reconstruction. |
| 1775 | Computer 136
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Demonstrating the Scalability of Spokes-and-Hub Magnet Designs |
| Liliana Edmonds1, Irene Kuang1, Elfar Adalsteinsson1,2, and Jacob White1 | ||
1Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 2Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States |
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Keywords: Low-Field MRI, Low-Field MRI The easily constructed Aubert ring-inspired “spokes-and-hub” magnets show promise as a topology for handheld MR imaging, particularly for educational purposes. In this paper we show the scalability of the spokes-and-hub design, and associated tools and RF signal processing, by scaling up the magnet. Constructing a 2x larger magnet yields a volume large enough to potentially image a finger (with which we hope to inspire students). We used our simulator to design and optimize the magnet topology, then constructed it from off-the-shelf small bar magnets, and verified its fields by direct Hall-effect measurements as well as indirectly through spin echoes. |
| 1776 | Computer 137
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EM shielded spiral RF coil design for array coil decoupling at ultra-low field MRI |
| Yonghyun Ha1, Kartiga Selvaganesan2, Chenhao Sun1, Zhehong Zhang2, Anja Samardzija2, Heng Sun2, Gigi Galiana1, and Todd Constable1 | ||
1Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States, 2Biomedical Engineering, Yale University, New Haven, CT, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems We introduced a new RF coil made with Moebius cable and RF shield bowl that can be tuned with relatively low capacitance and has good isolation between the coils at low field. B1 amplitude, isolation between the coils, and SNR of the NMR signal of the proposed coil were compared with reference coils (made with copper wire and Moebius cable without an RF shield). Both bench measurements and MR experiments have demonstrated that this coil performs well as part of a low field coil array. |
| 1777 | Computer 138
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Optimization and Construction of a Low-Field MRI System Using Permanent Magnets |
| Mikah Mellors1 and Rebecca Feldman2 | ||
1University of Toronto, Toronto, ON, Canada, 2University of British Columbia, Kelowna, BC, Canada |
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Keywords: Low-Field MRI, Magnets (B0) A low-field tabletop spoke-and-hub permanent magnet array was constructed and assessed for homogeneity as a B0 field. Spatial encoding in the x and y directions was achieved by tilting the hubs relative to one other to generate a linearly increasing field in the tilt direction. A non-array RF coil was designed and optimized for low field strengths, where the signal-to-noise ratio is limited by the weak signal from the sample. The optimized coil design was tuned and matched to the resonant frequency of the spoke-and-hub magnet. |
| 2686 | Computer 161
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Specific Absorption Rate (SAR) Simulations for Ultra-low-field (<0.1 T) MRI Systems |
| Javad Parsa1,2 and Andrew Webb1 | ||
1C.J.Gorter MRI center, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, 2Percuros B.V., Leiden, Netherlands |
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Keywords: Low-Field MRI, Safety, specific absorption rate, transmit efficiency, electromagnetic simulations Simulations of the magnetic and electric fields produced by RF coil commonly used at ultra-low field systems (from 0.05 to 0.1 tesla) have been performed. The highest SAR locations is present in tissues such as the nose and skull that are closest to the coil. Based on these simulations, the specific absorption rate (SAR) efficiency can be derived to ensure safe operation on point-of-care (POC) MRI systems. |
| 2687 | Computer 162
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Rapid transfer function-based transmission field shimming for safe and B1+ artefact free MRI of implantation sites |
| Mostafa Berangi1,2,3, Helmar Waiczies2, and Thoralf Niendorf1,2,3 | ||
1Berlin Ultrahigh Field Facility (B.U.F.F.), Berlin, Germany, 2MRI.TOOLS GmbH, Berlin, Germany, 3Charité – Universitätsmedizin Berlin, Berlin, Germany |
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Keywords: Safety, Parallel Transmit & Multiband Fixation of bone fractures with screws is common clinical practical including follow-up monitoring of the implantation site and of the healing process. MRI-based monitoring can be compromised by tissue heating and transmission field distortion. To overcome this challenge, this work uses parallel transmission using an optimal transmission vector. The proposed approach leverages a single EMF simulation without the implant, while the effect of implant electromagnetic scattered fields are estimated using a transfer matrix. Optimal shim vectors are computed by an optimization process using a multilevel genetic algorithm. Our findings demonstrate the feasibility and performance of the transfer function driven approach. |
| 2688 | Computer 163
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Workflow proposal to test SAR virtual observation points with convex optimization: application to intersubject variability at 11.7T MRI |
| Vincent Gras1, Edouard Chazel1, Nicolas Boulant1, Alexis Amadon1, and Michel Luong1,2 | ||
1CEA, CNRS, BAOBAB, Neurospin, University of Paris Saclay, Gif sur Yvette, France, 2IRFU, Paris Saclay University, Gif-sur-Yvette, France |
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Keywords: Safety, Brain Connectivity Efficient monitoring of the specific absorption rate (SAR) in parallel-transmission MRI is performed by evaluating the RF power deposition on specific SAR matrices called Virtual Observation Points (VOPs). But given the various sources of uncertainties that occur in practice (head placement, anatomy, precision of the body model to name a few), a challenging task remains to determine a suitable safety margin to be applied on the VOPs to offer a tradeoff between safety and scanning performance. In this work, as a first step towards this, we propose a workflow to tackle this problem for brain imaging at 11.7 Tesla. |
| 2689 | Computer 164
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Large-scale Modelling of Patient Motion for Head Coils at 7T |
| Amer Ajanovic1,2, Raphael Tomi-Tricot1,2,3, Joseph V Hajnal1,2, and Shaihan Malik1,2 | ||
1Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, LONDON, United Kingdom, 2London Collaborative Ultra high field System (LoCUS), London, United Kingdom, 3MR Research Collaborations, SIEMENS Healthcare Limited, Frimley, United Kingdom |
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Keywords: Safety, Simulations, ultra-high field, RF arrays and systems, parallel transmit coils The aim of this study is 2-fold. First, it is to demonstrate the practicality of using MARIE workflow to generate models with variation due to patient pose/motion. The second aim is to explore use of a simple 1st order linear model to visualise and predict the variation in B1+ and SAR with pose. Consequently, 4 different coils are simulated in more than 2200 positions with respect to body. Low variability in key metrics is observed. 1st order linear model relating position with these metrics is found to further reduce variability. |
| 2690 | Computer 165
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Relaxing exclusion criteria for human subjects in the UHF cardiac MRI with 8Tx/16Rx cardiac array using the SAR analysis for conductive implants. |
| Maxim Terekhov1, Ibrahim A. Elabyad1, David Lohr1, and Laura M. Schreiber1 | ||
1Chair of Molecular and Cellular Imaging, Comprehensive Heart Failure Center, University Hospital Würzburg, Wuerzburg, Germany |
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Keywords: RF Arrays & Systems, Safety The incomplete consensus regarding SAR safety in ultra-high-field MRI leads to a large variety of exclusion criteria for volunteer cohorts in the different centers, especially regarding the acceptance of conductive implants. Therefore, SAR analysis of new commercial transceiver arrays contributes to supplying local IRBs with information regarding the safety of human subjects. This study aimed to analyze SAR for a prototype of a new 8Tx/16Rx array for 7T cardiac MRI. The main goal was to analyze the array safety for human subjects with a different type of passive implant located outside of the array borders. |
| 2691 | Computer 166
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Local and Whole-Body SAR in UHF Body Imaging: Implications for Matrix Compression |
| Thomas M. Fiedler1, Mark E. Ladd1, and Stephan Orzada1 | ||
1German Cancer Research Center (DKFZ), Heidelberg, Germany |
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Keywords: Safety, RF Arrays & Systems RF safety of multi-channel transmit arrays is supervised with a set of matrices representing local SAR or whole-body SAR. As transmit arrays for body imaging have characteristics of both volume and local transmit coils, this study evaluates both SAR aspects: local and whole-body SAR. In all evaluated cases, the local SAR limit was reached before the whole-body SAR. Nevertheless, the whole-body SAR matrix can be used to reduce the number of local SAR matrices, reducing memory and computing time. |
| 2692 | Computer 167
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Towards Applying Deep Learning to Predict Rigid Motion-Induced Changes in Q-matrices from UHF-MRI pTx Simulations |
| Katherine Anna Blanter1, Alix Plumley1, Shaihan Malik2, and Emre Kopanoglu1 | ||
1Psychology, Cardiff University Brain Research Imaging Centre, Cardiff University, Cardiff, United Kingdom, 2Life Sciences & Medicine, Biomedical Engineering & Imaging Sciences, Department of Biomedical Engineering, King's College London, London, United Kingdom |
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Keywords: Safety, Parallel Transmit & Multiband, Specific absorption rate (SAR), ultra-high field MRI, deep learning Patient motion affects the specific absorption rate (SAR), a safety parameter in MRI. SAR is often calculated using so-called Q-matrices. We used conditional generative adversarial networks (cGANs) to estimate the effect of motion on magnitude from Q-matrices, which were extracted from body models simulated in a parallel-transmit (pTx) coil tuned to operate at 7T. Networks trained on Q-matrices from two positions were extrapolated to nine others. Network-predicted Q-matrices corresponded well with simulated ground truth motion-affected Q-matrices. |
| 2693 | Computer 168
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Patient-specific Local SAR estimation by combined field mapping and deep-learning method |
| Shao Che1,2, Zhuoxu Cui1,2, Jin Liu3, Siyuan Ding3, Peng Cao4, Xiaoliang Zhang5, Xin Liu1,2, Hairong Zheng1,2, Dong Liang1,2, and Ye Li1,2 | ||
1Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, 3United Imaging Research Institute of Innovative Medical Equipment, Shenzhen, China, 4The University of Hong Kong, Hongkong, China, 5Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: Safety, Safety A method is proposed for real time patient-specific local SAR estimation based on B1 field mapping and machine-learning. The axial component of RF E-field is estimated by electric property tomography (EPT) method from B1 field, and the transversal component of RF E-field is predicted by a cycleGAN model trained with EM simulation input data. The safety factor of peak local SAR estimation is analyzed for a large set of random transmit weighting factors and the feasibility of the method is discussed. |
| 2694 | Computer 169
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Experimental Validation of Deep Learning Based Local SAR Mapping from 3D B1+ and Localizer-like MRIs for 7T pTx Systems |
| Sayim Gokyar1, Chenyang Zhao1, and Danny JJ Wang1,2 | ||
1USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States, 2Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States |
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Keywords: Safety, Safety, Local SAR Prediction Local SAR related heating is a limiting safety factor at UHF MRI. Since local SAR cannot be measured, it should either be estimated from the global SAR or predicted by using the available data such as B1+ maps and MRIs. Here we proposed to use a multi-channel 3D CNN to utilize different channels for B1+ maps and MRIs simultaneously to improve local SAR prediction. We validated our method on 6 participants and found that maximum SAR values can be predicted with 80% accuracy, and local SAR variation can be predicted over 95% accuracy by using common image similarity metrics. |
| 2695 | Computer 170
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An open-source, low-cost 8-channel transmit/receive 3T head coil for pTx developments, MR safety testing and standardization |
| Christoph Stefan Aigner1, Mads Sloth Vinding2, Lukas Winter1, Reiner Montag1, Sebastian Schmitter1,3,4, Bernd Ittermann1, and Frank Seifert1 | ||
1Physikalisch-Technische Bundesanstalt (PTB), Berlin and Braunschweig, Germany, 2Aarhus University, Center of Functionally Integrative Neuroscience (CFIN), Department of Clinical Medicine, Faculty of Health, Aarhus, Denmark, 3Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 4University of Minnesota, Center for Magnetic Resonance Research, Minneapolis, MN, United States |
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Keywords: RF Arrays & Systems, New Devices This work investigates an open-source, low-cost 8-channel transmit/receive head coil to enable rapid and reproducible pTx development, safety assessment and evaluation at 3T. FDTD simulations were validated with phantom measurements on a 3T with an external pTx system. Relative and absolute 2D/3D B1+-maps were acquired to compute the CP+ mode, and two RF shims were tailored to enforce B1+ efficiency and homogeneity. The open-access design files could serve as a basis for new RF coil designs or pTx projects without needing high expertise in RF coil development or as a cost-effective alternative for multi-centre studies. |
| 2696 | Computer 171
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Temperature rise modelling framework for multiple electrode configurations on parallel transmit systems. |
| Jagjit S Sidhu1, Ken Sakaie1, Pallab K Bhattacharyya1, and Mark Lowe1 | ||
1Cleveland Clinic, Cleveland, OH, United States |
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Keywords: Safety, Safety Implanted electrodes can induce unsafe heating during MRI. Developing safe MRI protocols can be a burdensome process, involving intensive simulations that are hard to tailor to individual patients. To increase the feasibility of safe imaging of patients with implanted electrodes, we extend previous work, that nulled induced currents when the number of transmitters exceeded the number of electrodes, to account for the case when these are equal or the number of electrodes exceeds the number of transmitters. In such cases, complete nulling (no measured temperature rise) is impossible in all electrodes unless an acceptable induced temperature rise is allowed. |
| 2697 | Computer 172
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Optimized model architecture and generalization for deep learning-based SAR prediction (MRSaiFE) |
| Mina Chookhachizadeh Moghadam1, Nawal Panjwani2, Elizaveta Motovilova1, Mengying Zhang 1, Fraser Robb3, Adrian Hoang1, Tasmia Afrin1, and Simone Angela Winkler1 | ||
1Radiology, Weill Cornell Medicine, New York, NY, United States, 2Tandon School of Engineering, New York University, New York, NY, United States, 3GE Healthcare, Aurora, OH, United States |
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Keywords: Safety, High-Field MRI, Deep Learning, SAR prediction, Tissue heating Predicting the SAR distribution in ultra-high field MRI is a crucial task to prevent tissue damage due to the hotspots, though it is challenging. The MRSaiFE deep learning framework predicts SAR based on anatomical images, but it does not guarantee model generalization due to data leakage in the training process. To improve the model, we extended the UNet architecture to include residual and inception modules in its encoder part. Further, we implemented customized loss functions, and evaluation metrics to improve the predictive performance. The results show that the model predicts SAR with an SSIM=86% and MSE=0.14% for unseen body models. |
| 2698 | Computer 173
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Extreme Value Theory as a Risk Analysis Tool to Infer Specific Absorption Rate Intersubject Variability Safety Margins |
| Igor Tyshchenko1, Simon Lévy2, Bahman Tahayori3, and Leigh A. Johnston1 | ||
1Department of Biomedical Engineering, The University of Melbourne, Melbourne, Australia, 2MR Research Collaborations, Siemens Healthcare Pty Ltd, Melbourne, Australia, 3The Florey Institute of Neuroscience and Mental Health, Melbourne, Australia |
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Keywords: Safety, Parallel Transmit & Multiband, Safety margins, SAR estimation Specific absorption rate (SAR) in parallel transmission (pTx) ultra-high field MRI is typically evaluated by performing offline electromagnetic simulations on a generic human model. Conventionally, a safety margin that addresses the issue of intersubject variability is selected by choice of the 99th or higher percentile of the SAR distribution. In this work, we argue that this approach underestimates the risk of exceeding the SAR limit. As an alternative, we propose the use of Extreme Value Theory (EVT) for controlling the probability of extremal events in the form of large SAR deviations. |
| 2699 | Computer 174
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SAR and Temperature Safety Assessment on Patient Specific Models Generated with a Registration Method |
| Giuseppe Carluccio1,2, Eros Montin1, Christopher Michael Collins1,2, and Riccardo Lattanzi1 | ||
1Radiology, NYU Grossman School of Medicine, New York, NY, United States, 2Center for Advanced Imaging Innovation and Research (CAI2R), New York University, New York, NY, United States |
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Keywords: Safety, Safety Patient specific models are required to improve the accuracy of the simulations to perform safety assessment related to interaction of the RF fields with the body tissues. One registration method allows non-rigid transformations: this can be used to reshape a numerical body model to match the images of a patient, and generate a model similar to the shape of the patient. We performed SAR and temperature simulations to evaluate the ability of the registered model to perform a patient-specific safety assessment. The evaluation has been successful: the SAR and temperature patterns were corresponding to the ones of the target anatomy. |
| 2700 | Computer 175
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SAR Simulations with a Poseable Numerical Body Model for 3T MRI of Straight & Flexed Knee: First Results |
| Douglas Brantner1,2 and Christopher Collins1,2 | ||
1Radiology, NYU Grossman School of Medicine, New York, NY, United States, 2Center for Advanced Imaging Innovation and Research (CAI2R), New York University, New York, NY, United States |
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Keywords: Safety, Safety Although recent developments in flexible coils have allowed for imaging of the knee in a flexed or straight position, simulations for safety assessment are typically performed with both legs straight. Here we show first results of SAR simulations with both legs straight versus knee flexed with fields normalized as if imaging the knee that is changing position. Results indicate a decrease in maximum 10g SAR when the knee being imaged is flexed. |
| 2701 | Computer 176
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On the Importance of Solving for Temperature Versus Local SAR When Evaluating RF-Induced Heating in the Magnetic Resonance Environment |
| Eric David Anttila1, Grant M Baker1, Alan R Leewood1, and David C Gross1 | ||
1MED Institute, West Lafayette, IN, United States |
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Keywords: Safety, Safety Previous work has determined that solving for a weighted average local SAR is a relatively easy to way to estimate worst-case RF-induced heating in MRI. The purpose of this study was to determine the importance of solving for temperature using a sequentially coupled electromagnetics and heat transfer model versus local SAR alone when evaluating worst-case RF-induced heating. The results demonstrate that to fully capture RF-induced heating in MRI, temperature rise must be solved for using a sequentially coupled electromagnetic and heat transfer model due to the complex interplay of electric and thermal material properties for implants and the surrounding tissue. |
| 2702 | Computer 177
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Reducing the number of virtual observation points when utilizing populations of body models |
| Ehsan Kazemivalipour1,2, Markus W. May3,4, Jason P. Stockmann1,2, Robert L. Barry1,2, Boris Keil5,6, Lawrence L. Wald1,2,7, and Bastien Guerin1,2 | ||
1A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany, 4High-Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, 5Institute of Medical Physics and Radiation Protection, Department of Life Science Engineering, Mittelhessen University of Applied Sciences, Giessen, Germany, 6Center for Mind, Brain and Behavior (CMBB), Philipps-University Marburg, Marburg, Germany, 7Harvard-MIT Division of Health Sciences Technology, Cambridge, MA, United States |
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Keywords: RF Pulse Design & Fields, RF Pulse Design & Fields We introduce a VOP compression scheme using “stacked E-fields” followed by the removal of linear redundancies with a positive semi-definite convex optimization problem. This method provides a lower VOP-count at a constant SAR overestimation factor compared to three other approaches when applied to 7 Tesla 8-channel and 16-channel arrays loaded with three body models, each placed at three z-positions. The “stacked E-field” method yielded a compression factor of 0.0124% and 0.0039% for the 8-channel and 16-channel arrays, respectively, and 61% and 6% fewer VOPs than the standard VOP approach that does not remove linear redundancies. |
| 2703 | Computer 178
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Numerical Evaluation of Specific Absorption Rate of Local Transceiver Coil Arrays for Ultra-High Field MRI with Different Local Mesh Properties |
| Egor Berezko1, Georgiy Solomakha1, Klaus Scheffler2,3, and Nikolai Avdievich1 | ||
1High-field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, 2Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, 3Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany |
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Keywords: High-Field MRI, Safety Home-built RF UHF MRI coils have to be carefully evaluated for safety issues. This is performed by simulating the coil model, which often include thin conductors, loaded by a human voxel model. Currently such models are available mainly for time-domain solvers. Fine mesh over conductors and the large voxel model may lead to time-consuming simulations. Therefore, for smaller head-sized coils, the model has to be cut and the proper mesh size chosen. In this work, we numerically investigated the dependence of B1+ and SAR for four different head coils on fine local meshing and the size of the voxel model. |
| 2704 | Computer 179
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Numerical Simulation of SAR for a dual-frequency 1H/19F Body Coil array at 3 Tesla |
| Paul Mcelhinney1, Sarah Allwood-Spiers2, Graeme Keith1, Belinda Ding3, David Brennan4, Natasha Fullerton2, Celestine Santosh2,4, David Porter 1, and Shajan Gunamony1,5 | ||
1Imaging Centre of Excellence, University of Glasgow, Glasgow, United Kingdom, 2NHS Greater Glasgow & Clyde, Glasgow, United Kingdom, 3Siemens Healthcare Limited, Frimley, United Kingdom, 4Aurum Biosciences Limited, Glasgow, United Kingdom, 5MR CoilTech Limited, Glasgow, United Kingdom |
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Keywords: RF Arrays & Systems, Shims An eight-channel transceiver 1H/19F dual-frequency 3-Tesla body array has been developed to investigate the use of a perfluorocarbon (PFC) compound for use in as diagnostic tool in the investigation of inflammation inside the human body. Dual-frequency operation enables the same coil to be used at both frequencies, which reduces scan time, improves patient comfort, and provides accurate anatomic localisation. This RF coil consists of 8 transceiver elements, with four in each posterior and anterior half. This abstract presents the electromagnetic (EM) simulations for B1+ homogenisation, SAR assessment and validation of the dual-frequency array. |
| 2863 | Computer 161
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Use of Magnetic Materials to Mitigate RF-induced Heating in Active Implantable Medical Devices with 1.5T MRI |
| Md Zahidul Islam1, Ananda Kumar2, Jianfeng Zheng1, and Ji Chen1 | ||
1Univ of Houston, Houston, TX, United States, 2FDA, Silver Spring, MD, United States |
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Keywords: Safety, Safety The effect of ferrite magnetic beads to suppress the induced currents on a straight wire active implantable medical devices (AIMDs) lead was investigated. Leads with one, two and no ferrite beads were studied experimentally and using numerical simulations. The application of ferrite beads on the leads significantly reduced induced currents, and thus heating on experiments outside the MRI scanner. In the MRI magnet no significant reduction in heating was observed due to magnetic saturation of the ferrite beads. Suitable magnetic material for current suppression needs to be developed for application in MRI scanners. |
| 2864 | Computer 162
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RF-induced heating of interventional devices at 0.55T |
| Ali Caglar Özen1, Maximillian Russe2, Thomas Lottner1, Simon Reiss1, Sebastian Littin1, Maxim Zaitsev1, and Michael Bock1 | ||
1Division of Medical Physics, Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, 2Department of Radiology, University Medical Center Freiburg, Freiburg, Germany |
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Keywords: Safety, Interventional Devices, Low Field, RF-induced heating Low-field high-performance MRI systems at 0.55T are expected to cause less RF heating in conventional interventional devices compared to clinical 1.5T or 3T systems, which would facilitate MR-guided interventions significantly. Here we systematically evaluate the safety of intravascular devices through high-resolution electric field mapping, transfer function measurements, and realistic device trajectories from vascular models. Furthermore, the effects of patient size and positioning, target organ (liver and heart), and transmit body coil type are tested at a low-field RF test-bench for 6 commonly-used interventional devices (two guidewires, two catheters, an applicator and a biopsy needle). |
| 2865 | Computer 163
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Is MR-induced RF heating around implanted leads lower at 0.55 T than 1.5 T? Not necessarily. |
| Pia Panravi Sanpitak1, Bhumi Bhusal1,2, Jasmine Vu1,2, and Laleh Golestanirad1,2 | ||
1Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States, 2Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States |
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Keywords: Low-Field MRI, Low-Field MRI, Simulations Low-field MRI systems have been advertised as “safe” for patients with implants – but is this true? In a series of systematic simulations, we looked at implants with varied length, amount of coiling, and insulation during RF exposure in both 0.55 T and 1.5 T MRI environments. We found that both the actual and apparent length of the implant can significantly impact heating. There are several cases where heating is substantially higher at 0.55 T than 1.5 T, suggesting that no broad claims should be made, and these factors need to be carefully considered before scanning a patient. |
| 2866 | Computer 164
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New System, New Approach: Fasten up transfer function validation measurements, prove of concept |
| Finya Ketelsen1,2 and Gregor Schaefers1,3 | ||
1MRI-STaR - Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany, 2TU Dortmund University, Dortmund, Germany, 3MR:comp GmbH, Testing Service for MR Safety & Compatibility, Gelsenkirchen, Germany |
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Keywords: Safety, Safety, Implants, RF-induced heating The novel open 64 MHz linear exposure system offers new possibilities for the test process of active implants for RF-induced heating as a safety issue. This study proves the concept, that the measurements for the validation process of the transfer function, which models the electric behavior of an active implant, could be accelerated from hours of precise work to minutes without any rearranging. Because the system is open, there is significantly more space than in a birdcage coil and the object and measuring probe can be mounted to a movement system, that can access the whole phantom. |
| 2867 | Computer 165
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Comparison of the electric field and its line integral along the lead of a device across five different RF transmit coils |
| Lydia J Bardwell Speltz1,2, Seung-Kyun Lee3, Yunhong Shu1, Matt Tarasek3, Joshua D Trzasko1, Thomas KF Foo3, and Matt A Bernstein1 | ||
1Department of Radiology, Mayo Clinic, Rochester, MN, United States, 2Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN, United States, 3GE Global Research, Niskayuna, NY, United States |
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Keywords: Safety, Safety We introduce a method to calculate lead-tip voltage for implanted devices by considering 1) the individualized lead path extracted from X-ray-based images, 2) the incident electric field per unit B1+rms derived for the RF transmitter and a digital human body model, 3) the complex RF wavenumber in an insulated conductor derived from antenna theory. T/R coil transmitters in whole-body at 1.5T and 3.0T were considered, as well as a head coil on a compact 3T. Based on leads in 10 subjects, the results show the compact 3T produces less lead tip voltage than whole-body T/R coils. |
| 2868 | Computer 166
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RF Safety Measurements of External Defibrillator Electrodes: E-Field and Temperature Mapping |
| Simon Reiss1, Ali Caglar Özen1, Thomas Lottner1, and Michael Bock1 | ||
1Division of Medical Physics, Department of Radiology, University Medical Center Freiburg, Freiburg, Germany |
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Keywords: Safety, Safety Currently, no external defibrillation system is available that is labeled MR safe. To create an MR safe device heating induced by the electrodes that are attached to the patient needs to be prevented. In this study, we propose a setup for high resolution RF E-field mapping of commercially available defibrillation electrodes and show that this setup can be used to precisely detect hot spots. At these hot spots, we then perform temperature measurements within a 1.5T to assess the MR safety of the electrodes. |
| 2869 | Computer 167
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A Modular Parallel Radiofrequency Transmission System Platform for MRI Safety Investigations at 3 T |
| Benson Yang1, Fred Tam1, Maryam Arianpouya2, Cathleen Leone1, Vicki Li1, Jason Rock2, and Simon Graham1,2 | ||
1Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada, 2Medical Biophysics, University of Toronto, Toronto, ON, Canada |
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Keywords: RF Arrays & Systems, New Devices Parallel radiofrequency transmission (pTx) continues to show great promise in resolving MRI challenges at higher magnetic field strengths. Commercial pTx MRI systems can be very costly with limited system channel count options. This work presents the current state of an 8-channel pTx MRI system with expansion flexibility up to 32-channels that is based on software-defined radio technology. |
| 2870 | Computer 168
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A New Method to Improve RF Safety of Implantable Medical Devices using Inductive Coupling at 3.0T MRI |
| Bu S Park1, Joshua Guag2, Sunder Rajan2, and Brent McCright3 | ||
1FDA, Silver Spring, MD, United States, 2Division of Biomedical Physics (DBP), FDA, Silver Spring, MD, United States, 3Division of Cellular and Gene Therapies (DCGT), FDA, Silver Spring, MD, United States |
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Keywords: Safety, Electromagnetic Tissue Properties This study describes a new method to improve RF safety of implantable medical devices located outside of the imaging region by using a secondary resonator (SR) to reduce electric fields and corresponding specific absorption rate (SAR) during MRI. The SR is designed to produce opposing electro-magnetic fields (EM-fields) compared to the EM-fields made by a body coil at 3.0T. This study was performed using numerical simulations with ASTM phantom and human models, and corresponding experimental verifications with the ASTM phantom. Keywords: RF safety, secondary resonator |
| 2871 | Computer 169
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RF exposure of patient assistants at a low-field open MRI system |
| Sukhoon Oh1, Seon-Eui Hong2, Hyung-Do Choi2, Dongwoo Chang3, Kiseong Kim4, and Sangwoo Kim5 | ||
1Korea Basic Science Institute, Cheongju, Korea, Republic of, 2Electronics and Telecommunications Research Institute, Daejeon, Korea, Republic of, 3Chungbuk National University, Cheongju, Korea, Republic of, 4BioBrain, Inc., Daejeon, Korea, Republic of, 5Daewon University College, Jechoen, Korea, Republic of |
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Keywords: Safety, Safety Numerical investigations on the safety of patient assistants exposed to a 1.2T open MRI are performed at different poses of patient assistants (including wearing latex gloves), because current regulations are concerned with only patient RF safety. Compared with the patient, up to 29.8% of the patient 10-gram SAR was observed in the patient assistant. To prevent possible RF hazards of a patient assistant during MRI scans, certain clauses regarding the patient assistant’s poses or wearing gloves must be added to the existing MRI screening forms. |
| 2872 | Computer 170
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Consideration of peripheral nerve stimulation in the optimization of spiral k-space trajectories |
| Oliver Schad1,2, Tobias Wech1, and Herbert Köstler1 | ||
1Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Würzburg, Germany, 2University of Würzburg, Experimental Physics 5, Würzburg, Germany |
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Keywords: Gradients, Safety, Peripheral Nerve Stimulation The algorithm we present in this work designs variable density spiral (VDS) trajectories and their respective gradient time courses based on the Stanford VDS-tool. In addition to hardware limits (maximum gradient strength and slew rate) a PNS threshold based on the SAFE-Model is introduced. |
| 2873 | Computer 171
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Physiological variability of the tympanic membrane temperature as an RF safety metric assessment |
| Caroline Le Ster1, Mikhail Kozlov2, Alexandre Vignaud1, and Nicolas Boulant1 | ||
1University of Paris‐Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, 2Department of Neurophysics, Max Plank Institut for Human Cognitive and Brain Sciences, Leipzig, Germany |
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Keywords: Safety, Thermometry RF exposure during MR exams induces heating of the exposed tissues. Measurement of tympanic membrane temperature with an infrared sensor has been used to estimate non-invasively the global RF-induced temperature rise. In this study, the tympanic membrane temperature was measured before and after having the volunteers lying for 15 minutes with earplugs with neither an RF nor a static magnetic field. Large physiological variations of temperature rise were observed across the volunteers after this dummy “exposure”, showing the low reliability of this metric to measure small temperature rises, that make it problematic for RF-induced temperature rise estimation. |
| 2874 | Computer 172
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MR conditionality of two MR Conditional DBS ipsilateral implants with separate IPGs |
| Louai Aldayeh1, Mizan Rahman1, and Ross Venook1 | ||
1Boston Scientific Neuromodulation, Valencia, CA, United States |
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Keywords: Safety, Safety Previous investigations of RF-induced heating of multiple implants (active as well as passive) have shown that heating of an implant can be impacted by the presence of a separate neighboring implant. This work assessed to which extend this phenomenon is present for the limited scope of two separate MR Conditional ipsilateral DBS implants, one on one side of the body, and another on the other side. Both, RF-induced heating and voltage injection level into the IPG were assessed. A variety of DBS lead configurations, and clinically relevant distances in-between the two separate implants, were thoroughly assessed for a data-driven conclusion. |
| 2875 | Computer 173
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MRI Gradient Induced Vibration of Leadless Pacemakers |
| Michael Childers1, Dorab Sethna1, and Shiloh Sison2 | ||
1Abbott, Sylmar, CA, United States, 2Abbott, Sunnyvale, CA, United States |
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Keywords: Safety, Safety, Implants Simulations were performed to assess potential gradient induced vibration of leadless pacemakers. Results of the evaluation showed leadless pacemakers sized objects, made from commonly used conductive materials, generated very small vibrations (all less than 0.3mm in displacement) when exposed to conservative gradient induced vibration safety test conditions per ISO/TS 10974. These calculated displacements are negligible in comparison to the interacting displacements between a typical leadless pacemaker and cardiac tissue through each cardiac cycle. As such, the risk of leadless pacemaker gradient induced vibration tissue damage is minimal and assessments for this hazard per ISO/TS 10974 may not be necessary. |
| 2876 | Computer 174
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A novel PNS measurement setup for body gradient coils at an ultrasonic driving frequency of 20kHz |
| Michael JB McGrory1, Edwin Versteeg1, Jeroen CW Siero1,2, and Dennis WJ Klomp1 | ||
1Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2Spinoza Center for Neuroimaging, Amsterdam, Netherlands |
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Keywords: Gradients, Gradients Large dB/dt swings in gradient coils can induce peripheral nerve stimulation (PNS) in the human body. This limits the slew rates used in whole-body MRI reducing scan speeds and spatial resolution. Ultrasonic head gradients can enable fast and silent imaging, however extension to whole-body gradients is challenging due to the required larger dB/dt swings. In this work, we present a body gradient coil which can be used to investigate PNS induction at an ultrasonic driving frequency of 20kHz. |
| 2877 | Computer 175
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Behavioural and functional assessment of mice inner ear after chronic exposure to an ultra-high static magnetic field of 11.7T or 17.2T. |
| Caroline Le Ster1, Erwan Selingue1, Roseline Poirier2, Jean-Marc Edeline2, Sébastien Mériaux1, and Nicolas Boulant1 | ||
1University of Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, 2University of Paris-Saclay, CNRS, NeuroPSI, Saclay, France |
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Keywords: Bioeffects & Magnetic Fields, Animals High static magnetic (B0) fields are known to induce a transient disturbance of the inner ear. Recently a study demonstrated long-term behavioural effects in mice chronically exposed to a B0 field of 16.4T. In the current study, mice underwent chronic B0 exposure at 11.7T or 17.2T and longitudinally performed behavioural tests over the study. An auditory brainstem response (ABR) test was performed at the end of the full exposure period to assess inner ear properties. Despite the transient disturbance of mice inner ear observed immediately after B0 exposure, no short-term or long-term alteration was detected with behavioural or ABR tests. |
| 2878 | Computer 176
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Working Harder at MRI Safety, But Getting Poorer MRI Safety Results. |
| Tobias Gilk1,2 | ||
1Gilk Radiology Consultants, Overland Park, KS, United States, 2RADIOLOGY-Planning, Kansas City, MO, United States |
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Keywords: Safety, Safety US data suggests that MRI adverse events are growing at a rate of nearly 3x the rate of MRI examinations. While MRI accidents and injuries remain infrequent, the long-term trend of significant growth in MRI adverse events highlights needs for vigilance in MRI safety. |
| 2879 | Computer 177
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Influence of arm rotations on peripheral nerve stimulation thresholds for the interventionalist in MR guided procedures |
| Feng Jia1, Sebastian Littin1, Philipp Amrein1, Maximilian Frederik Russe2, and Maxim Zaitsev1 | ||
1Division of Medical Physics, Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, Freiburg, Germany, 2Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, Freiburg, Germany |
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Keywords: Safety, Safety, PNS Simulation Simulation of peripheral nerve stimulation of MRI gradient coils for rotated arms of an interventional radiologist. The arm rotation has a direct influence on the site of stimulation in the arm. |
| 3721 | Computer 141
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A tailored coil for sensitive detection of MRI signals in modulating the rat’s blood-brain barrier by focused ultrasound and microbubbles at 7T |
| Sheng-Kai Wu1,2, Alessandro De Maio1,2, Hsin-Ju Lee1,2, Kullervo Hynynen1,2, Meaghan O'Reilly1,2, and Fa-Hsuan Lin1,2 | ||
1Sunnybrook Research Institute, Toronto, ON, Canada, 2University of Toronto, Toronto, ON, Canada |
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Keywords: Multimodal, Non-Array RF Coils, Antennas & Waveguides Imaging-guided focused ultrasound using MRI can modulate the permeability of blood-brain barrier with high spatial accuracy. However, many MRI-guided FUS studies rely on either a body coil or head coil poorly suited to the FUS system geometry. We developed a tailored receiver coil to improve the sensitivity of 7T MRI for rats. The tailored geometry allows for a 30% SNR increase in a study modulating the blood-brain barrier permeability with microbubbles. |
| 3722 | Computer 142
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Quadrature Transceiver RF Arrays Using Double Cross Magnetic Wall Decoupling for Ultrahigh field MR Imaging |
| KOMLAN PAYNE1, Aditya Ashok Bhosale1, Leslie Lei Ying1, and Xiaoliang Zhang1 | ||
1Department of Biomedical Engineering, University at Buffalo, Buffalo, NY, United States |
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Keywords: Hybrid & Novel Systems Technology, RF Arrays & Systems Circularly polarized or quadrature transceiver coils can significantly increase overall signal reception and reduce the excitation power over linearly polarized RF transceivers. Due to the wave propagation of two modes owing to their electromagnetic field properties, it is challenging to achieve sufficient decoupling in multichannel quadrature coil arrays. In this work, we proposed a double cross magnetic wall decoupling for quadrature transceiver RF arrays based on a common-mode differential-mode (CMDM) resonator at UHF 7T. The proposed method comprised of two orthogonal decoupling elements is able to reduce the mutual coupling between the multi-modes in a pair of CMDM resonators. |
| 3723 | Computer 143
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Analysis of the interactions between a TMS coil and a standard receive-only RF loop for MR imaging at 3T |
| Lucia Navarro de Lara1,2, Qinglei Meng1,2, Jason P Stockmann1,2, Sergey Makarov1,2,3, Mohammad Daneshzand1,2, Larry L Wald1,2, and Aapo Nummenmaa1,2 | ||
1Martinos Center for Biomedical Imaging/MGH, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Worcester Polytechnic Institute, Worcester, MA, United States |
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Keywords: Hybrid & Novel Systems Technology, Hybrid & Novel Systems Technology, TMS/fMRI Specialized MR hardware is needed to combine non-invasive brain stimulation methods (e.g., TMS) and concurrent acquisition of functional MR images. Such integrated hardware systems enable studying causal relationships between the cortical and subcortical nodes of large-scale brain networks. For best possible imaging performance, all interactions of the stimulation coils on the transmit, encoding and receive system of the MR system should be analyzed on detail. The presented approach enables quantitatively assessing the influence of the TMS coils on MR imaging receive hardware. Understanding the effects could lead to improved design strategies for integrated TMS/MRI systems. |
| 3724 | Computer 144
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A Rotatable Twisted Solenoid TRASE Phase Gradient Head Coil |
| Christopher J Sedlock1, Aaron R Purchase1, Boguslaw Tomanek 1, and Jonathan C Sharp1 | ||
1University of Alberta, Edmonton, AB, Canada |
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Keywords: Hybrid & Novel Systems Technology, RF Arrays & Systems, TRASE TRASE is an MR encoding sequence that utilizes phase gradients of the RF transmit field for k-space encoding. A promising RF coil for TRASE imaging is the twisted solenoid due to its compact design and efficient B1 field. In this work we present the first TRASE head coil, consisting of a geometrically decoupled parallel-transmit (pTx) rotatable twisted solenoid pair. No RF switching hardware is required. The encoding direction of this coil pair is set by rotation angle, allowing for 2D radial k-space acquisitions. This method is compatible with the addition of a static B0 slice selection gradient for multi-slice.
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| 3725 | Computer 145
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Miniature and flexible Bazooka balun for MRI RF coils |
| Shuyang Chai1,2 and Xinqiang Yan1,2 | ||
1Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, 2Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States |
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Keywords: New Devices, New Devices Flexible receive coil design has been researched on for a long time. However, several challenges is still presenting. One of them is the still bulky and rigid balun. Here we exhibit a novel flexible bazooka balun. It can be built on any coaxial cable and is formed by heat shrinks and braided wires. The flexible balun is smaller than conventional balun in length and size. |
| 3726 | Computer 146
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In-bore Preamplifier Nonlinearity Calibration |
| Chris Vassos1, John Pauly1, Fraser Robb2, Shreyas Vasanawala3, and Greig Scott1 | ||
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2GE Healthcare, Aurora, OH, United States, 3Radiology, Stanford University, Stanford, CA, United States |
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Keywords: Hybrid & Novel Systems Technology, System Imperfections: Measurement & Correction Present MRI preamplifiers are very linear but use 10s of mA bias current and over 150mW power. For wireless arrays, low power alternatives based upon SiGe transistors are needed. These achieve the needed gain and noise figure, with order of magnitude power reduction, but at the cost of increased nonlinearity. Using pilot tone technology, we present a calibration system for preamplifier nonlinearity correction targeted to low power SiGe preamplifiers. This system integrated a phase-locked SDR into a form of prescan to demonstrate that in-bore preamplifier linearity calibration and correction are possible. |
| 3727 | Computer 147
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Comparing 8-channel and 4-channel head array coils for 7T human brain Deuterium MRS imaging (DMRSI) applications |
| Xin Li1, Soo Han Soon1, Matt Waks1, Hannes M. Wiesner1, Xiao-Hong Zhu1, and Wei Chen1 | ||
1Department of Radiology, University of Minnesota, Minneapolis, MN, United States |
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Keywords: RF Arrays & Systems, Non-Proton Deuterium MRS imaging (DMRSI) has emerged as an important neuro-metabolic imaging tool. We compared the performance of 4-channel and 8-channel deuterium head array coils for 7T human brain DMRSI through electromagnetic simulation, phantom and in vivo measurements. Both simulation and phantom studies show that the 4-channel array coil produced more than twice the RF magnetic field (B1) than the 8-channel array coil. Whole-brain DRMSI data with high spatial (0.7 cc nominal voxel) and temporal (2.5 min) resolutions was collected from five healthy subjects using a 4-channel head array coil, showing excellent SNR throughout the human brain. |
| 3728 | Computer 148
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ADC Repeatability and Reproducibility of NCI CIRP Network Pre-Clinical MRIs |
| Dariya Malyarenko1, Ghoncheh Amouzandeh1,2, Stephen Pickup3, Rong Zhou3, Henry Charles Manning4, Seth T Gamon4, Kooresh I Shoghi5, James D Quirk5, Renuka Sriram6, Peder Larson6, Michael T Lewis7, Robia G Pautler7, Paul E Kinahan8, Mark Muzi8, and Thomas L. Chenevert1 | ||
1Radiology, University of Michigan, Ann Arbor, MI, United States, 2neuro42, San Francisco, CA, United States, 3Radiology, University of Pennsylvania, Philadelphia, PA, United States, 4Cancer Systems Imaging, The University of Texas MDACC, Houston, TX, United States, 5Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, United States, 6Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, 7Baylor College of Medicine, Houston, TX, United States, 8Radiology, University of Washington, Seattle, WA, United States |
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Keywords: System Imperfections: Measurement & Correction, Precision & Accuracy The goal of this work was to assess ADC repeatability, reproducibility, and bias of Co-Clinical Imaging Research Resource Program (CIRP) network MRIs using standardized procedures for comparison to corresponding performance of clinical MRIs. A temperature-controlled phantom provided an absolute reference standard and means to assess spatial uniformity of these metrics. Seven institutions participated in the study where DWI were acquired over multiple days on 10 pre-clinical scanners, from 3 vendors at 6 field strengths. Technical level repeatability and reproducibility metrics, and spatial uniformity patterns are comparable to that observed on human systems using similar phantoms and test procedures. |
| 3729 | Computer 149
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Can a 38-channel dipolectric antenna array compete with a 32-channel commercial head coil at 7T? |
| Thomas Dardano1,2, Lijing Xin1,2, and Daniel Wenz1,2 | ||
1CIBM Center for Biomedical Imaging, Lausanne, Switzerland, 2Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland |
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Keywords: RF Arrays & Systems, RF Arrays & Systems In this work we explore a concept of dipolectric antenna array up to 38 receive channels. We constructed and evaluated an 8-channel version of dipolectric antenna array for human brain MRI at 7T and benchmarked its receive performance against a commercial 1Tx/32Rx head coil. In vivo data obtained for 8-channel array along with simulations (16- and 38-channel) indicate that a 38-channel dipolectric antenna array could provide significantly higher SNR than the current state-of-the-art solutions for human brain at 7T. |
| 3730 | Computer 150
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Twisted pair coils as flexible receive elements for 7 T - SNR and active detuning efficiency |
| Raphaela Czerny1, Roberta Frass-Kriegl1, Veronika Cap1, Elmar Laistler1, and Lena Nohava1 | ||
1High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Flexible RF Coils Form-fitting coil designs demand highly flexible coils such as twisted pair or coaxial transmission line resonators. Both of these designs and respective interfacing circuits were investigated as receive-only coils at 7 T. Similar signal-to-noise ratio and active detuning performance compared to a standard copper wire coil were demonstrated in bench and MRI experiments. |
| 3731 | Computer 151
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Development of 1H/23Na dual-tuned RF probe using inductive coupling for 9.4T vertical wide-bore superconducting MRI for rat’s kidney |
| Naoto Momiyama1, Tomoyuki Haishi2, and Yasuhiko Terada1 | ||
1Graduate School of Science and Technology, University of Tsukuba, Tsukuba, Japan, 2Department of Radiological Sciences, International University of Health and Welfare, Narita, Japan |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Proton A superconducting magnet for vertical NMR, commonly used as a high-field magnet, is effective for the MRI of X nuclides with low detection sensitivity. Even in a narrow magnetic field space, an inductively coupled RF coil with a simple structure can be used to image small animals one size larger. In this study, to visualize 23Na distribution in the kidney region of anesthetized rats, we developed 1H/23Na dual-tuned RF coils using inductive coupling with a 9.4T wide bore magnet (room temperature bore diameter 89 mm) and performed in vivo imaging. |
| 3732 | Computer 152
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Stretchable Coil for Small Animal MRI |
| Thejas Vishnu Ramesh1, Folk W. Narongrit2, and Joseph V. Rispoli1,2,3 | ||
1Biomedical Engineering, Purdue University, West Lafayette, IN, United States, 2Electrical and Computer Engineering, Purdue University, West Lafayette, IN, United States, 3Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Small Animal MRI This work demonstrates a simple, easy to use, stretchable coil system for small animal MRI at 7T. Phantom images obtained using the stretchable coil were analysed for coil SNR. The SNR of the stretchable coil was compared with SNR of a standard commercial coil. Ex-vivo imaging of a mouse and rat brain was also performed. Current work involves minimizing SNR reduction due to coil stretch. Future work involves developing a 4-channel stretchable coil array for in-vivo imaging of a rat brain. |
| 3733 | Computer 153
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15-Channel Head Cap Array using Twisted-Pair Elements for MRI |
| Julian Adolfo Maravilla1, Colin Taylor Knizek2, Nazem Khairallah1, Ana Claudia Arias1, and Michael Lustig1 | ||
1EECS, University of California, Berkeley, Berkeley, CA, United States, 2University of California, Berkeley, Berkeley, CA, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems, Flexible RF Array, Conformal RF Array, fMRI Sleep Studies, TMS/EEG/fMRI A tight fitting and wearable 15-Channel Head Cap Array using Twisted-Pair Elements was designed and characterized for potential use in a multimodal imaging system. The RF Array was characterized in terms of safety and SNR. The elements in the array (Twisted-Pair coil) show >40dB isolation for active detuning with no significant component heating under harsh RF conditions (ΔT<4°C). SNR evaluations revealed a 3x increase in peripheral SNR and retainment of SNR under parallel imaging conditions when compared to a commercial head array. An array of this caliber can be used for fMRI sleep studies and simultaneous TMS/EEG/fMRI. |
| 3734 | Computer 154
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Toward a Size-Adaptable 128-Channel Receive RF Coil for Human Head Imaging at 3T Using a Flexible Plate Approach |
| William Mathieu1, Charbel Matta1, Milica Popović1, and Reza Farivar2 | ||
1Electrical and Computer Engineering, McGill University, Montreal, QC, Canada, 2Ophthalmology, McGill University, Montreal, QC, Canada |
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Keywords: RF Arrays & Systems, RF Arrays & Systems We present a size-adaptable flexible-plate 128-channel receive coil design with initial results. Our approach allows for increased element density as elements can be placed closer to the surface of the scalp. Arrays are built on semi-flexible plates with boundaries roughly following cranial sutures. The aim is to accommodate at least 99% of head shapes and sizes. Our 18-channel “occipital” plate array (1 of 8 plates) was compared to the posterior portion (40-channels) of the Siemens 64 Head/Neck coil using SNR maps. Results show that our design improves average and max SNR by 1.9- and 7.4-fold, respectively. |
| 3735 | Computer 155
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Stretchable conductive-thread MRI receive array coils for the knee |
| Folk W. Narongrit1, Thejas Vishnu Ramesh2, and Joseph V. Rispoli1,2,3 | ||
1Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, United States, 2Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States, 3Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, United States |
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Keywords: RF Arrays & Systems, New Devices, Coils, Stretchable We report on the development of an 8-channel stretchable array coils for 3T knee MRI which was rapidly designed using embroidered conductive threads on athletic fabric. The coil is omnidirectionally stretchable and conforms to the anatomy. Phantom testing shows the coil’s signal-to-noise ratio (SNR), and image quality are comparable to a commercial flexible coil. In vivo imaging was done on a healthy volunteer illustrates the potential of rapidly developed stretchable coils. |
| 3736 | WITHDRAWN |
| 3737 | Computer 156
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B1 improvement of a birdcage coil using a flexible metamaterials at 7 T |
| Sergio Solis-Najera1, Jelena Lazovic2, Rodrigo Ruiz1, Fabian Vazquez1, and Alfredo Odon Rodriguez3 | ||
1Departamento de Fisica, UNAM, Mexico City, Mexico, 2Department of Physical Intelligence, Max Planck Institute for Intelligent Systems, Stuttgart, Germany, 3Electrical Engineering, UAM Iztapalapa, Mexico City, Mexico |
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Keywords: RF Arrays & Systems, RF Arrays & Systems This work presents a flexible metasurface to improve the B1 and the image SNR of a transceiver quadrature birdcage coil for preclinical MRI applications at 7 T. The metasurface was not tuned so no passive components were used. The imaging phantom was entirely covered with the metasurface and produced an improvement of both B1 and the SNR. This easy-to-implement approach offers an alternative to improve the B1 field for preclinical applications at high field.
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| 3738 | Computer 157
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Design of a high power RF amplifier with configurable number of channels |
| Jifeng Chen1,2, Ye Li1,2, Zhenhua Shen3, Bin Liu3, Xiaoliang Zhang4, Bin Cao3, Xin Liu1,2, Xu Chu3, and Hairong Zhen1,2 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, 3Shanghai United Imaging Healthcare, Shanghai, China, 4Department of Biomedical Engineering, State University of New York at Buffalo, New York, NY, United States |
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Keywords: RF Arrays & Systems, Parallel Transmit & Multiband, RF power amplifier UHF (Ultra high field) MRI requires high RF power from RF Power Amplifier (RFPA), especially for whole-body imaging1. Some studies on body imaging reported limitation on available RF power. In this study, we present works to provide RFPA with highest peak power capability known for UHF MRI with configurable number of transmit channels so as to meet different RF coil requirements. Feasibility and performance of the new method in UHF MRI was demonstrated on the bench and 5T whole-body scanner. |
| 3739 | Computer 158
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RF FRONT-END RECEIVER USED IN 1.5T MRI |
| Anvesh Inamdar1, Sanket Gothankar1, Bhaskar Niak1, and Rajesh Harsh1 | ||
1Medical Systems Division, SAMEER, Mumbai, India |
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Keywords: RF Pulse Design & Fields, RF Pulse Design & Fields, RF Front-end In an MRI, the receiver coil produces moderately low signals that are difficult to detect in a noisy environment. As a result, there was a requirement for a customised RF front end that could tolerate high power leakage from coils, provide adequate isolation, low noise figure, and have a good gain factor. The developed RF front end complies with the requirements and produces images with low noise |
| 3895 | Computer 141
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Low field Breast and Chest Wall Imaging for MR guided Proton Therapy |
| Neha Koonjoo1,2, Torben P.P Hornung1,2,3, Susu Yan3,4, Matthew S Rosen1,2,5, and Thomas R Bortfeld3,4 | ||
1Department of Radiology, A.A Martinos Center for Biomedical Imaging / MGH, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Department of Physics, ETH Zürich, Zürich, Switzerland, 4Department of Radiation Oncology, MGH, Boston, MA, United States, 5Department of Physics, Harvard University, Cambridge, MA, United States |
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Keywords: Low-Field MRI, Breast, Hybrid & Novel System Technology The use of low field MRI guidance in proton therapy is a new area of research especially during treatment of breast cancer. In this study, we optimized and constructed five different breast/chest RF coils at low field as proof of concept for a future MR guided proton therapy system design. Different coil shapes and sizes were tested. Organs-at-Risk (OAR) and different anatomical regions were optimized for imaging. Using the five coils, phantom images were acquired at 6.5 mT and MR signal across slices were compared to the calculated optimized B1 field homogeneity. Human breast imaging was also carried out. |
| 3896 | Computer 142
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Knee MRI Using a Wireless and Passive Metasurface Coil |
| Yi Yi1, Zhonghai Chi2, Yakui Wang1, Maopeng Wu2, Lixue Wang1, Deqing Jiang1, Li He1, Xihai Zhao3, Yonggang Meng2, Ji Zhou4, Qian Zhao2, and Zhuozhao Zheng1 | ||
1Department of Radiology, Beijing Tsinghua Changgung Hospital, School of Medicine, Tsinghua University, Beijing, China, 2State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing, China, 3Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, 4State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing, China |
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Keywords: New Devices, Non-Array RF Coils, Antennas & Waveguides, Metasurface Metasurface is an effective solution to enhance SNR of MRI images. Here, we propose a wireless and passive metasurface coil and evaluate its performance in knee MRI. Phantom studies suggest improved image uniformity compared to the conventional phased-array radio-frequency coils. In vivo knee MRI of volunteers suggests higher image quality scores and better contrast of knee cartilage in metasurface groups. When used in conjunction with the spine coil, the metasurface coil provides a favorable SNR between that of the 4- and 12-channel phased-array coil. It is more convenient, cost-effective, and applicable to 1.5T MRI systems from different manufacturers. |
| 3897 | Computer 143
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High permittivity ceramics for improving detection of fMRI activation at 1.5T |
| Vladislav Koloskov1, Mikhail Zubkov1, Georgiy Solomakha1, Viktor Puchnin1, Anatoliy Levchuk1,2, Alexander Efimtcev1,2, Irina Melchakova1, and Alena Shchelokova1 | ||
1School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation, 2Department of Radiology, Federal Almazov North-West Medical Research Center, St. Petersburg, Russian Federation |
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Keywords: Hybrid & Novel Systems Technology, Hybrid & Novel Systems Technology, high permittivity materials, SNR enhancement We show that high permittivity materials (HPMs) can improve functional magnetic resonance imaging (fMRI) at 1.5T, increasing the receive sensitivity of a commercial multi-channel head coil. Both numerical simulations and experiment showed ~25% improvement in the signal-to-noise ratio (SNR) of a commercial head coil in the areas of interest when HPM blocks were placed in proximity. This led to an increase in the detected motor cortex fMRI activation volume by an average of 56%, thus resulting in more accurate functional imaging at 1.5T. |
| 3898 | Computer 144
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Improving signal-to-noise ratio and contrast in Wrist Magnetic Resonance Imaging at 1.5T with Wireless Metasurface Resonantor |
| Yakui Wang1, Zhonghai Chi2, Yi Yi1, Maopeng Wu2, Lixue Wang1, Deqing Jiang1, Li He1, Xihai Zhao3, Yonggang Meng2, Ji Zhou4, Qian Zhao2, and Zhuozhao Zheng1 | ||
1Department of Radiology, Beijing Tsinghua Changgung Hospital, School of Medicine, Tsinghua University, Beijing, China, 2State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing, China, 3Center for Biomedical Imaging Research, Department of Biomedical Engineering,School of Medicine, Tsinghua University, Beijing, China, 4State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing, China |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Joints, Metasurface We designed a wireless metasurface resonator(WMR) for wrist magnetic resonance imaging(MRI) at 1.5T and tested the imaging effect. Phantoms and 14 wrist jionts(7 healthy volunteers) were examed with T1W SE and fat-suppressed PDW FSE sequences at a 1.5T MRI system. Commercial 12-channel wrist array coil(12CH-WR) and WMR(coupling with integrated spine coil) were used to receive MR signal respectively. We found that WMR could improve the image SNR by 1.5~2 times, and significantly improve the image contrast compared with the traditional 12CH-WR. |
| 3899 | Computer 145
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The Metaslab: A combined Metamaterial and Metasurface for Improved Transmit Performance and Use as a Receive Array. |
| Lauren Smart1, Adam Mitchell Maunder2, Ashwin K. Iyer1, and Nicola De Zanche2 | ||
1Electrical and Computer Engineering, University of Alberta, Edmonton, AB, Canada, 2Oncology, Medical Physics, University of Alberta, Edmonton, AB, Canada |
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Keywords: RF Arrays & Systems, Body, metamaterial Abdominal and thoracic imaging at 3T suffers from inhomogeneous transmit fields and hot-spots in specific absorption rate (SAR) that limit image quality and imaging efficiency, respectively. We combine a lightweight metamaterial and metasurface (the ‘metaslab’) to enhance transmit efficiency and homogeneity, as well as to reduce SAR. The metaslab is further able to operate as a receive array with four distinct sensitivity patterns and sensitivity comparable to that of a conventional 4-element loop receive array. The metaslab is much lighter than comparable dielectric pads and achieves all these benefits in a similar package as a conventional coil array. |
| 3900 | Computer 146
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High impedance quadrature receivers array for magnetic resonance skin imaging at 7T |
| Komlan Payne1, Aditya A. Bhosale1, Yunkun Zhao1, and Xiaoliang Zhang1 | ||
1Department of Biomedical Engineering, University at Buffalo, Buffalo, NY, United States |
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Keywords: Hybrid & Novel Systems Technology, RF Arrays & Systems The study of skin diseases is by far among the difficult research in biomedical field. Nowadays, many techniques are available to perform skin examination. Magnetic Resonance Imaging (MRI), a non-invasive technique can provide detailed image of the skin. For such procedure, a whole-body coil can be used as the transmitter while receivers array coils are placed in close proximity of the region of interest. In this abstract we design an array of high impedance quadrature detectors with good decoupling performance for skin image at 7T. |
| 3901 | Computer 147
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Transceiver 8Tx/32Rx array with L-shaped loop elements for accelerated cardiac MRI at 7T: initial optimization and experimental testing. |
| Maxim Terekhov1, Ibrahim A. Elabyad1, David Lohr1, Anna Frey2, Florian Schnitter2, and Laura M. Schreiber1 | ||
1Chair of Cellular and Molecular Imaging,Comprehensive Heart Failure Center, University Hospital Würzburg, Wuerzburg, Germany, 2Department of Internal Medicine I, Cardiology, University Hospital Würzburg, Wuerzburg, Germany |
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Keywords: RF Arrays & Systems, Parallel Transmit & Multiband, cardiovascular The concept of the L-shaped loop elements architecture with the antisymmetric arrangement was applied to develop a 8Tx/32Rx transceiver array for cardiac MRI at 7T. This work aimed to check B1+ shimming and parallel imaging capabilities of the array and to perform the initial testing in human thorax phantom and pig cadaver. Both phase-only and pTX optimization modes demonstrated the possibility for efficient shaping of B1+ with an optimized spatial homogeneity. Despite the sub-optimal geometry of the pig thorax, the array demonstrated a good B1+ coverage of the heart region with no apparent destructive interferences. |
| 3902 | Computer 148
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Towards Dense Flexible Transceive Coil Array: Comparison Study of Coaxial Dipoles for 7T Human Torso MRI. |
| Jules Vliem1,2, Raphael Tomi-Tricot1,3,4, Irena Zivkovic2, and Özlem Ipek1,3 | ||
1Biomedical Engineering, Kings's College London, London, United Kingdom, 2Electrical Engineering, Technical University of Eindhoven, Eindhoven, Netherlands, 3London Collaborative Ultra high field System (LoCUS), King's College London, London, United Kingdom, 4MR Research Collaborations, Siemens Healthineers, Frimley, United Kingdom |
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Keywords: RF Arrays & Systems, High-Field MRI In this work, we explored properties of various coaxial dipole designs and compared them with the conventional dipole. Dipoles were fabricated of RG58 coaxial cable and the total length was 34cm. S-parameters and flip angle maps of individual elements and array configurations were measured on a torso phantom. Comparison of flip angle maps shows very similar performances of all examined dipoles with the coaxial dipole being slightly advantageous. When placed in densely populated array configuration, coaxial dipoles were sufficiently decoupled and produced expected B1+ maps. Coaxial dipole shows promising performances to be used in a densely populated flexible torso array. |
| 3903 | Computer 149
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Performance comparisons of different single-channel coils using different materials |
| Chunhu Song1,2, Qiaoyan Chen1,2, Shao Che1,2,3, Haining Wang3, Xiaoliang Zhang4, and Ye Li1,2 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, 3Shanghai United Imaging Healthcare, Shanghai, China, 4Department of Biomedical Engineering, State University of New York at Buffalo, New York, NY, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems The ultra-flexible RF coil can fit the image subjects well and thus improve signal-to-noise ratio (SNR). In this study, four types of single-channel receiver coils using different materials with the same size were constructed. Phantom studies were performed on a 3T MRI system. As a result, the liquid metal coil can achieve a most similar performance as the conventional copper coil, while the liquid metal coil is more flexible. This demonstrates that the liquid metal coil has a good application potential in imaging curved anatomical structures. |
| 3904 | Computer 150
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A Wrap-on Decoupled Coaxial Transmission Line (CTL) Transceive Array for Head MR Imaging at 10.5T |
| Xiaoliang Zhang1, Lance DelaBarre2, Komlan Payne1, Matt Waks2, Gregor Adriany2, and Kamil Ugurbil2 | ||
1Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States, 2Radiology, University of Minnesota, Minneapolis, MN, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems In this work, a wrap-on 447MHz transceiver array using the 2nd mode of coaxial transmission line resonator is designed, constructed and tested for human head imaging at the ultrahigh field of 10.5T. Results demonstrate the unique decoupling performance among the resonant elements achievable even for non-overlapped array layouts. The 10.5T images of a human head phantom acquired from the proposed array along with numerical simulations are shown. |
| 3905 | Computer 151
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Estimating noise figure of matching networks for low-input-impedance preamplifiers |
| Wenjun Wang1, Juan Diego Sánchez Heredia2, Vitaliy Zhurbenko1, and Jan Henrik Ardenkjær Larsen2 | ||
1National Space Institute, Technical University of Denmark, Kongens Lyngby, Denmark, 2Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark |
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Keywords: RF Arrays & Systems, RF Arrays & Systems, matching The noise figure of a matching network between a receive coil and a preamplifier with low input impedance can be estimated using relationship \(F\approx1+R_{11}/R_\mathrm{c}\). It is demonstrated how to use this relationship to choose optimal matching-decoupling network topology in terms of signal-to-noise ratio (SNR). The formula serves as an efficient tool to estimate noise figure of matching networks and is useful in low-field and high-coil-Q applications, where the noise of the matching network becomes comparable to coil noise. |
| 3906 | Computer 152
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Multi-channel, Stretchable, Self-Tuning Coil Array Based on Liquid Metal Technology |
| Elizaveta Motovilova1, Terry Ching2, Jana Vincent3, Ek Tsoon Tan4, Victor Taracila3, Michinao Hashimoto2, Fraser Robb3, Darryl Sneag4, and Simone Angela Winkler1 | ||
1Departmetn of Radiology, Weill Cornell Medicine, New York, NY, United States, 2Engineering Product Development Pillar, Singapore University of Technology and Design, Singapore, Singapore, 3GE Healthcare, Aurora, OH, United States, 4Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems, Liquid metal, Stretchable RF coils Stretchable receive coils can provide conformal fitting, improved SNR, and dynamic imaging capabilities. However, conductor stretching alters the resonance frequency, reducing potential SNR advantages. Previously, we proposed and demonstrated in a single element prototype a smart self-tuning coil design which allows to maintain the desired Larmor frequency with stretching. This work investigates the applicability of self-tuning techniques in a multi-channel stretchable coil array and demonstrates its performance in silico and in vitro. Simulation results show stable resonance frequency (<1%) and sensitivity (±5%) for varied load/stretching conditions. In vitro imaging demonstrates consistent performance of individual coil elements and the array (SNR=146). |
| 3907 | Computer 153
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Quantitative evaluation of two-dimensional flexible metasurfaces at 3.0 T |
| Karthik Lakshmanan1,2, Alena Schelokova3, Stanislav Glybovski3, Mary Bruno1, and Christopher Collins1,2 | ||
1Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, NYU Grossman School of Medicine, New york, NY, United States, 2Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, NYU Grossman School of Medicine, New york, NY, United States, 3ITMO University, St. Petersburg, Russian Federation |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, RF Arrays & Systems Quantitative evaluation of transmit efficiency and receive-specific SNR were performed for two different metasurfaces in a body-sized phantom for cases with 1) excitation and reception using the system body coil and 2) excitation with the system body coil and reception with a commercial 12-element array. Similar evaluations were performed for one of the metasurfaces in vivo with the receive array present, and for comparisons all measurements were also made with no metasurface present. Both metasurfaces were seen to significantly improve transmit efficiency in all cases, and to improve SNR when the body coil was used for reception, with effects being strong near the metasurface and extending toward the center of the phantom. The metasurfaces had minimal effects on receive SNR of the commercial Rx array. |
| 3908 | Computer 154
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Investigating the effect of ultra-High Dielectric Constant (uHDC) ceramic disk placement on RF coil performance for optimal MRI applications |
| Xin Li1, Hannes M. Wiesner1, Xiao-Hong Zhu1, and Wei Chen1 | ||
1Department of Radiology, University of Minnesota, Minneapolis, MN, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, RF Arrays & Systems It has been demonstrated that integrating ultra-High Dielectric Constant (uHDC) materials with a RF coil can achieve large improvement in RF magnetic field (B1) and imaging sensitivity. A typical configuration inserts the uHDC materials between the imaging object and the RF coil, resulting in a weak B1 from the coil due to the distance from the object. In this study, we explored different configuration options and found that the best arrangement was to place the uHDC materials outside the coil, leaving no gap between the RF coil and the object, for optimal imaging applications. |
| 3909 | Computer 155
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Remote detection MRI using a flexible non-selective metamaterial at 7 T |
| Sergio Solis-Najera1, Jelena Lazovic2, Fabian Vazquez1, and Alfredo Odon Rodriguez3 | ||
1Departamento de Fisica, UNAM, Mexico City, Mexico, 2Department of Physical Intelligence, Max Planck Institute for Intelligent Systems, Stuttgart, Germany, 3Electrical Engineering, UAM Iztapalapa, Mexico City, Mexico |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, RF Arrays & Systems, travelling-wave We propose a method to remotely acquire MR images at 7 T with a preclinical imager using a bio-inspired surface coil, a parallel-plate waveguide and a non-selective metamaterial. Phantom images were acquired with and without a flexible metasurface inserted in cylindrical phantom filled with saline solution and a birdcage coil. Uniformity profiles were computed for all cases showing that the birdcage coil and metasurface profiles have a very good correspondance. An improvement was observed for the images obtained with the metasurface. This approach offers a convenient alternative to obtained high quality images. |
| 3910 | Computer 156
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A coupled planar RF array for ultrahigh field MR imaging |
| Yunkun Zhao1, Komlan Payne1, Leslie YIng1, and Xiaoliang Zhang1 | ||
1Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: New Devices, Spinal Cord This study proposes a coupled planar radio frequency (RF) array for spine imaging at 7T. Multiple identical loop coils are closely placed to achieve strong EM coupling in order to form a multimodal resonator. This coupled resonator can design large high-frequency RF coils for ultrahigh field imaging applications in humans. |
| 3911 | Computer 157
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Considerations for Accurate Active Detuning Measurements in Densely Parallel Array Coils |
| Manisha Shrestha1, Mirsad Mahmutovic1, Sam-Luca JD Hansen1, Jason P Stockmann2, and Boris Keil1 | ||
1Institute of Medical Physics and Radiation Protection, TH Mittelhessen University of Applied Sciences, Giessen, Germany, 2A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States |
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Keywords: RF Arrays & Systems, High-Field MRI, detuning Active detuning of receive array coil during transmit prevents large currents being induced in the coil which could damage sensitive electronic components and create SAR hotspots. The standard method of adjusting active detuning using a double probe shows an offset in the resonant frequency set at bench when tested in the presence of a scanner. Setting a high impedance at the input of loop using S11 measurement exactly at Larmor frequency has proven to be a better method to detune loops actively.
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| 3912 | Computer 158
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Design of a Highly Decoupled Compact Dual-tuned Transceiver RF Coil Arrays for 1H MRI and 31P MRSI at 7T |
| KOMLAN PAYNE1, Aditya Ashok Bhosale1, Leslie Lei Ying1, and Xiaoliang Zhang1 | ||
1Department of Biomedical Engineering, University at Buffalo, Buffalo, NY, United States |
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Keywords: Parallel Imaging, Multimodal, Dual nuclear In this work, we developed a decoupled multichannel double-tuned RF coil array for 1H/31P MR imaging and spectroscopy at the ultrahigh field of 7T. One of the difficulties in designing such high-frequency double-tuned coil arrays is to electromagnetically decouple the two frequency channels simultaneously. To address this issue, we designed a double-crossed magnetic wall (or ICE) decoupling which can independently and simultaneously decouple the 1H channels and 31P channels. With the improved performance, this developed 1H/31P transceiver array is expected to offer improved detection quality and imaging speed in 1H/31P metabolic imaging applications at 7T. |
| 3913 | Computer 159
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Boosting Central Head SNR at 10.5T: 32-channel Hybrid RF Coil Comprised of 25 Rx-only Loops and 7 TxRx NODES Dipoles |
| Alireza Sadeghi-Tarakameh1, Matt Waks1, Andrea Grant1, Jeromy Thotland1, Russell L Lagore1, Lance DelaBarre1, Edward Auerbach1, Pierre‐Francois Van de Moortele1, Gregor Adriany1, Kamil Ugurbil1, and Yigitcan Eryaman1 | ||
1Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, MN, United States |
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Keywords: RF Arrays & Systems, High-Field MRI Higher signal-to-noise ratio (SNR) is the primary maxim for increasing the magnetic field strength of MRI scanners. However, RF coils comprised of loops do not capture the highest achievable SNR that is theoretically available at ultrahigh field (defined as ≥7T) MRI. In this study, we investigate the hypothesis of increasing central head SNR at 10.5T by combining loop and dipole receiver elements. For this purpose, we manufactured a 32-channel hybrid RF coil comprised of 25 receive-only loops and 7 transceiver NODES dipoles. This 32ch hybrid coil achieved ~80% higher central SNR compared to a 32ch loop array. |
| 4071 | Computer 141
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En Route to Body and Cardiac MRI at 21.0 T: Where does the RF power dissipate? |
| Bilguun Nurzed1, Dennis Hieronymi1, Thomas Wilhelm Eigentler1, and Thoralf Niendorf1,2,3 | ||
1Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, 2Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine, Berlin, Germany, 3MRI.TOOLS, Berlin, Germany |
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Keywords: RF Arrays & Systems, Bioeffects & Magnetic Fields Investigation of the power correlation matrix at 21.0 T is vital to elucidate the electrodynamics for human body and cardiac MR as well as the RF antenna performance. Recognizing this opportunity, this abstract assesses the power losses for multi-channel RF transceiver arrays for human body and cardiac MR using 32-channel pTx/Rx self-grounded bow-tie building block (SGBT). Losses were determined inside the tissue, lossy material of the antenna, lumped elements of the tuning and matching network and due to coupling and radiation. |
| 4072 | Computer 142
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Design of calibration-free RF pulses for T2-weighted single-slab 3D turbo-spin-echo sequences at 7T utilizing parallel transmission |
| Daniel Löwen1, Eberhard Daniel Pracht1, Vincent Gras2, Aurelien Massire3, Franck Mauconduit2, Nicolas Boulant2, and Tony Stöcker1,4 | ||
1German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, 2Université Paris-Saclay, Commissariat à l’Energie Atomique, CNRS, NeuroSpin, BAOBAB, Gif sur Yvette, France, 3Siemens Healthineers, Saint-Denis, France, 4Department of Physics and Astronomy, University of Bonn, Bonn, Germany |
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Keywords: High-Field MRI, RF Pulse Design & Fields, Brain, Parallel Transmit & Multiband Multi-Slice T2-weighted MR imaging is a fundamental technique in brain imaging but suffers from field inhomogeneities at ultra-high field systems. In this work we present a pulse design method which provides slab-selective universal pulses with phase-coherent excitation profiles over selected brain regions. Applied in a 3D variable flip angle turbo-spin-echo (TSE) sequence, the pulses achieve superior SNR compared to multi-slice TSE imaging and B1+ field inhomogeneity mitigation. |
| 4073 | Computer 143
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Simultaneous multi-slice 23Na imaging using radial CAIPIRINHA |
| Marco L. Wittrich1,2, Armin M. Nagel1,3, Sebastian Schmitter1,4, Peter Bachert1,2, Mark E. Ladd1,2,5, and Fabian J. Kratzer1,2 | ||
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany, 3University Hospital Erlangen, Institute for Radiology, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU), Erlangen, Germany, 4Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany, 5Faculty of Medicine, University of Heidelberg, Heidelberg, Germany |
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Keywords: High-Field MRI, Non-Proton, 23Na,SMS,radial CAIPIRINHA In this work, a simultaneous multi-slice (SMS) approach using radial CAIPIRINHA was implemented for sodium MRI. Initial experiments were confined to two simultaneously excited slices. Here, simulated and measured slice profiles agreed well with expectations. Further, the SNR of the acquired SMS images was analyzed and compared to reference measurements of the individual slices. An SNR increase of up to 38% when maintaining flip angle and up to 13% for constant SAR was observed. Lastly, in-vivo head images (2.9x2.9x12mm3) were obtained showing the feasibility of 23Na SMS MRI. |
| 4074 | Computer 144
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Investigating the impact of head position on the spatial distribution of B1+ field for a 60-ch Tx coil at 7T |
| Hecheng Jin1, Andrea N Sajewski1, Tales Santini1, Tiago Martins1, Jacob P Berardinelli1, Anthony DeFranco1, Howard J Aizenstein1, and Tamer S Ibrahim1 | ||
1University of Pittsburgh, Pittsburgh, PA, United States |
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Keywords: High-Field MRI, Simulations, Head position, B1+ field, 7T MRI In this work, we computationally and experimentally evaluated the B1+ field and SAR generated by a 60-channel Tic-Tac-Toc RF coil at 7T MRI scanner on a variety of participants, head models and head positions. On three anatomically detailed human head models, we found slight changes in the intensity and the distribution of B1+ field and SAR over the whole brain when the head was moved out from the top of the coil. This was confirmed in both simulation and experimental B1+ maps. Our results highlighted the impact of imaging setup on imaging quality. |
| 4075 | Computer 145
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Investigating the Optimal Number of Channels in an Array System for Human Head Imaging at 7T |
| Aditya Ashok Bhosale 1, Leslie Ying1, and Xiaoliang Zhang1 | ||
1Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: High-Field MRI, RF Arrays & Systems To determine the optimal number of channels employed in an array system for Human Head imaging at 7T, we examined different multi-channel circular LC loop array systems, ranging from 4-channel to 64-channel arrays. |
| 4076 | Computer 146
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Preliminary SNR comparison between the 11.7T Iseult RF coil and its twin coil at 7T |
| Alexis Amadon1,2,3, Vincent Gras1,2,3, Edouard Chazel1,2,3, Paul-François Gapais1,2,3, Franck Mauconduit1,2,3, Alexandre Vignaud1,2,3, Nicolas Boulant1,2,3, and Michel Luong2,4 | ||
1NeuroSpin, CEA, Gif-sur-Yvette, France, 2Paris-Saclay University, Gif-sur-Yvette, France, 3Baobab, CNRS, Gif-sur-Yvette, France, 4IRFU, CEA, Gif-sur-Yvette, France |
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Keywords: High-Field MRI, High-Field MRI, 11.7T, Signal-to-Noise Ratio The Iseult coil, developed for MRI of the human brain at 11.7T, was presented at last year’s ISMRM meeting. Here we show SNR phantom measurements in comparison with the Avanti2 coil, a replica of the Iseult coil tuned at 300 MHz (for 7T). We derive a new power dependence of the SNR vs B0. |
| 4077 | Computer 147
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Background Field Inhomogeneity Correction for High-Resolution T2* Mapping of the Human Cervical Spinal Cord at 7T |
| Seyedeh Nasim Adnani1,2, Sultan Zaman Mahmud1,2, Thomas S. Denney1,2, and Adil Bashir1,2 | ||
1Department of Electrical and Computer Engineering, Auburn University, Auburn, AL, United States, 2Auburn University MRI Research Center, Auburn University, Auburn, AL, United States |
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Keywords: High-Field MRI, Spinal Cord, T2* mapping, Artifacts Ultra-high-field (UHF) Spinal Cord (SC) imaging could be helpful in detecting subtle pathological changes in the human SC. The increased effect of magnetic field inhomogeneity at UHF on T2* renders the quantification unreliable. Therefore, the field correction methods are critical. We have demonstrated the application of the Voxel Spread function method, to address this issue in human SC at 7T. F-term correction was applied to the pre-processed SC images, and the T2* values were reported for SC GM and WM both before and after field inhomogeneity correction. VSF reduces magnetic field inhomogeneity effects for quantitative T2* mapping in human SC. |
| 4078 | Computer 148
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7T to 3T domain adaptation in white matter lesion segmentation on T2-weighted (T2-w) FLAIR images using deep learning |
| Jinghang Li1, Eduardo Diniz2, Taylor Forry3, Tamer Ibrahim1,4, Howard Aizenstein1,4, and Minjie Wu4 | ||
1Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States, 2Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, PA, United States, 3Temple University, Philadelphia, PA, United States, 4Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States |
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Keywords: High-Field MRI, Machine Learning/Artificial Intelligence In this work, we explored the domain adaptation problem in deep learning segmentation. Specifically, we applied the residual U-net [1] on 3T and 7T Fluid Attenuated Inverse Recovery (FLAIR) images to delineate the white matter hyperintensity (WMH) in a 2D fashion. We leveraged learning without forgetting [2] to regulate the network’s learning in the new domain to preserve the model’s performance on the old domain while still achieving satisfying results on the new domain images. |
| 4079 | Computer 149
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Compact 16T MRI Magnet: Feasibility Study and Risk Reduction |
| Minfeng Xu1, Steve Buresh1, Anbo Wu1, Shike Huang1, and Thomas Foo1 | ||
1Global Research, General Electric, Niskayuna, NY, United States |
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Keywords: High-Field MRI, Magnets (B0), Superconducting Magnet; 16 T An electromagnetic design of a 16.0 T MRI magnet using a combination of Nb3Sn and NbTi superconductors has been completed. It consists of a 9.0 T inner Nb3Sn solenoid and a set of outer NbTi coils that produces 7.0 T field, for a combined 16.0 T field. The design revealed very high hoop tensile and axial compressional stresses in the Nb3Sn coil. Alloy-reinforced high-strength Nb3Sn wires were selected for use in this project. For a magnet to operate in a persistent mode, superconducting joints between Nb3Sn wire segments need to be developed. Various joint configurations were attempted with some success. |
| 4080 | Computer 150
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Design of dual-band Coaxial‐transmission‐line coils with independent tuning capabilities |
| Komlan Payne1, Aditya A. Bhosale1, Yunkun Zhao1, and Xiaoliang Zhang1 | ||
1Department of Biomedical Engineering, University at Buffalo, Buffalo, NY, United States |
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Keywords: High-Field MRI, Multimodal Recently, intensive research has been conducted on coaxial‐transmission‐line (CTL) RF coils for nuclear magnetic resonance (NMR) at frequency ranging from high field to ultra-high field. The flexibility of CTL is to some extent required to image dynamic anatomy of the human body. Analysis on the CTL coils based on transmission line theory has revealed multimode operating frequency. Consequently, CTL coils can be useful to implement dual-nuclear RF coil resonator designed for Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS). In this abstract, we design a dual-band CTL with independent tuning capabilities. |
| 4081 | Computer 151
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Bilateral Orthogonality Generating Acquisitions Method for Homogeneous T2* Images Using Dual Channel Parallel Transmission at 7T |
| Celik Boga1 and Anke Henning1 | ||
1UT Southwestern Medical Center, Dallas, TX, United States |
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Keywords: High-Field MRI, RF Pulse Design & Fields The T2*contrast specifically benefits from 7T human MRI systems and is frequently used in Neuroimaging. However, B1+ and B0 inhomogeneity at 7T limits the effectiveness of the T2*. A method originally proposed to minimize channel effects in the field of telecommunications, was adopted to a dual channel parallel transmission (pTx) human 7T MRI system. Final images are obtained by the unique combination of four small angle GRE acquisitons with adjusted flip angles for each channel. The proposed method is easy to implement, robust and provides homogeneous T2* images of the whole brain. |
| 4082 | Computer 152
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Evaluation of 8-Channel Transmit Dipoles and 8-Channel Transmit Loops for Pediatric Visual Cortex Imaging at 7T |
| Pedram Yazdanbakhsh1,2, Christian Sprang1,3, Marcus Couch4, Richard Hoge1,2,3, Christine Lucas Tardif1,2,3, and David A. Rudko1,2,3 | ||
1McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, QC, Canada, 2Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada, 3Department of Biomedical Engineering, McGill University, Montreal, QC, Canada, 4Siemens Healthcare Limited, Montreal, QC, Canada |
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Keywords: High-Field MRI, RF Arrays & Systems An 8-channel transmit radiofrequency (RF) coil array consisting of eight dipoles and another 8-channel transmit coil array consisting of 8-loops were designed, constructed and compared with each other for pediatric (4-9 years old) visual cortex imaging at 7T. To ensure robust safety of the 7T parallel-transmission (pTx) coil, local SAR matrices and the commensurate virtual observation points (VOPs) has been calculated for online SAR supervision. An 8-channel receive only array consisting of eight overlapped loops covering the back of the pediatric head area has been constructed and used inside the transmit coils for visual cortex imaging. |
| 4083 | Computer 153
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Significant Signal-to-Noise Ratio (SNR) Enhancement with Ultrahigh Dielectric Constant (uHDC) Ceramic Disks for 2H MRSI Application at 7T |
| Soo Han Soon1,2, Hannes M. Wiesner1, Xin Li1, Michael T. Lanagan3, Qing X. Yang4, Xiao-Hong Zhu1, and Wei Chen1,2 | ||
1Center of Magnetic Resonance Research (CMRR), Department of Radiology, University of Minnesota, Minneapolis, MN, United States, 2Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States, 3Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA, United States, 4Center for NMR Research, Department of Neurosurgery and Radiology, College of Medicine, Pennsylvania State University, Hershey, PA, United States |
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Keywords: High-Field MRI, New Devices, Ultrahigh dielectric constant material (uHDC) Ultrahigh-field (UHF) deuterium (2H) magnetic resonance spectroscopy imaging (DMRSI) is valuable to study neuroenergetics by quantitatively measuring the energy metabolic rates in the human brain. However, the low intrinsic signal-to-noise ratio (SNR) of deuterium signal due to its low gyromagnetic ratio and low metabolites concentration has been a technical challenge to achieving high imaging resolution. In this study, we have integrated ultrahigh dielectric constant (uHDC) ceramic disks with an 8-channel 2H-1H human head array coil to largely improve the receive sensitivity and DMRSI SNR (>60%) at 7T, aiming for human brain metabolic imaging application. |
| 4084 | Computer 154
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Understanding Loss Mechanisms in Double-Tuned Body Coils To Improve B1 Efficiency |
| Busra Kahraman-Agir1, Dimitri Welting1, Mark Gosselink1, and Dennis Klomp1 | ||
1Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands |
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Keywords: High-Field MRI, Non-Array RF Coils, Antennas & Waveguides, multinuclei body coils, double tuned Double-tuned circuits are often comprised of internal resonances in tank circuits that locally may amplify RF currents and thereby cause extra loss compared to single tuned RF coils. Here, we investigated the loss mechanisms of RF borecoils for the operating frequencies of 120.68, 78.8 and 45.8MHz for the purpose to design a B1+ efficient multi-tuned RF borecoil for metabolic MRI of 2H, 23Na and 31P, respectively at 7T.
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| 4085 | Computer 155
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Enhancing performance of a bio-inspired surface coil wtih a flexible metasurface for preclinical MRI at 7 T |
| Sergio Solis-Najera1, Jelena Lazovic2, Fabian Vazquez1, Rodrigo Martin1, and Alfredo Odon Rodriguez3 | ||
1Departamento de Fisica, UNAM, Mexico City, Mexico, 2Department of Physical Intelligence, Max Planck Institute for Intelligent Systems, Stuttgart, Germany, 3Electrical Engineering, UAM Iztapalapa, Mexico City, Mexico |
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Keywords: High-Field MRI, Non-Array RF Coils, Antennas & Waveguides, metamaterials A bio-inspired surface coil was built for preclinical MRI applications at 7 T. Images were acquired with and without a flexible metasurface partially cover a cylindrical phantom. Images obtained with the metamaterial showed an important improvement of coil performance. No electronic components were used for tuning the metasurface. This easy-to-implement approach offers an alternative to improve the SNR for preclinical applications at high field. |
| 4086 | Computer 156
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Exploration of the shielded-coaxial-cable coil as transceive array element for 9.4T MRI |
| Giovanni Costa1, Margarethus Maarten Paulides1, and Irena Zivkovic1 | ||
1Department of Electrical Engineering, Technical University of Eindhoven, Eindhoven, Netherlands |
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Keywords: High-Field MRI, High-Field MRI, RF arrays, transcieve coils, SCC coil The recently proposed shielded-coaxial-cable (SCC) coils are intrinsically highly decoupled elements. Their suitability in multichannel transceiver arrays at ultra-high field was successfully demonstrated in 7T arrays. In this work, we investigated the single element and array properties of SCC coils at 9.4T. We simulated the SCC element and compared its properties (B1+, SAR) with those of a conventional loop coil. Subsequently, we fabricated eight SCC coils and investigated their coupling properties when placed in various configurations. SCCs at 400MHz provided similar B1+ and SAR efficiency, but generated ~25% less SAR10g,max . SCC performed well in different array configurations. |
| 4087 | Computer 157
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A Comparison of Cartesian MR Fingerprinting Maps acquired at 3T and 7T |
| Saba Shirvani1, Belinda Ding2, and Christopher T. Rodgers1 | ||
1Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom, 2Research and Collaboration UK, Siemens Healthcare Ltd, Frimley, United Kingdom |
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Keywords: High-Field MRI, High-Field MRI, body, mr fingerprinting, tissue characterization Abdominal 7T MRI is technically demanding but has great potential due to improved signal-to-noise ratio. One promising way to quantify tissue properties is to use MR Fingerprinting, since MRF rapidly quantifies T1 relaxation alongside other tissue properties such as T2, B1+ and proton density. However, translating MRF measurements from high field to ultra-high field systems is challenging. Here we investigate a strategy to translate a Cartesian MRF sequence from 3T to 7T scanners, by optimising sequence parameters. We apply this approach to the brain and to the kidney and present comparable images from our 3T and 7T scanners. |
| 4088 | Computer 158
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3D Deep Learning Segmentation of White Matter Hyperintensity on 3T and 7T Brain MRI Scans |
| Yuanzhe Huang1, Jinghang Li1, Linghai Wang1, Taylor Forry2, Tamer Ibrahim1, Howard Aizenstein1, and Minjie Wu1 | ||
1University of Pittsburgh, Pittsburgh, PA, United States, 2Temple University, Philadelphia, PA, United States |
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Keywords: High-Field MRI, Machine Learning/Artificial Intelligence White matter lesions (WMLs), commonly found as hyperintensities (WMHs) on T2-weighted FLAIR MR brain images, are associated with neuropsychiatric and neurodegenerative disorders. In the present study, we adapted a 3D U-Net deep learning method to automatedly segment the WMHs on 3T and 7T MRI T2w FLAIR brain images. Using 3D U-Net, the accuracy of WMH segmentation is 98.8% for 3T data, while it drops to 90.3% for 7T data. However, after incorporating histogram matching in the preprocessing, the accuracy of WMHs segmentation significantly improves to 97.5% for 7T data. |
| 4089 | Computer 159
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Effects of spatial resolution on brain tissue displacement estimates based on DENSE MRI at 7T |
| Amelia Strom1,2, Timothy G. Reese2,3, Zijing Dong2,3, Baarbod Ashenagar4, Laura D. Lewis2,4, and Jonathan R. Polimeni1,2,3 | ||
1Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, 2Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, 3Department of Radiology, Harvard Medical School, Boston, MA, United States, 4Department of Biomedical Engineering, Boston University, Boston, MA, United States |
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Keywords: High-Field MRI, Tissue Characterization, Neurofluids, Diffusion Imaging Techniques Displacement Encoding with Stimulated Echoes (DENSE) MRI was used to estimate pons and midbrain tissue displacement over the cardiac cycle at 2-mm, 3-mm, and 4-mm isotropic spatial resolutions in individual subjects at 7T. Displacement estimates were largest at 2-mm resolution and matched previous reports of peak brainstem displacement over the cardiac cycle. Smaller estimates at lower resolution may be due to partial volume effects from the surrounding tissue or CSF. |
| 4090 | Computer 160
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Susceptibility Managed Optimization (SUMO) : Very HIgh order shimming for Single Voxel Spectroscopy at 7T |
| Hoby Hetherington1, Junghwan Kim2, Melissa Terpstra2, and Jullie Pan2 | ||
1Resonance Research Inc., Billerica, MA, United States, 2Radiology, University of Missouri, Columbia, MO, United States |
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Keywords: Shims, Shims B0 shimming for single voxel spectroscopy (SVS) is of importance due to its role in determining linewidth, accuracy of the analysis and interpretation. However, for difficult brain regions, such as the prefrontal cortex, where shifts of 3-6mm in voxel position can dramatically alter the achieved linewidth in SVS, the lack of a reliable method to predict the achievable homogeneity results in failed studies and/or increased study times. In this work we demonstrate an objective and non-iterative method (SUMO) for voxel positioning that predicts and ensures adequate B0 homogeneity is achievable. |
| 4226 | Computer 141
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Design of an improved Open-Face birdcage for human whole brain imaging at 5T |
| Zidong Wei1,2,3, Qiaoyan Chen1,2, Qiang He3, Xiaoliang Zhang4, Xin Liu1,2, Hairong Zheng1,2, and Ye Li1,2 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, 3Shanghai United Imaging Healthcare, Shanghai, China, 4Department of Biomedical Engineering, State University of New York at Buffalo, New York, NY, United States |
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Keywords: High-Field MRI, Brain The clinical experience, especially for subjects with claustrophobia, is not friendly when using the conventional shielded birdcage head coils on the ultra-high field. The closed structure also does not better support motion detection and motion correction, and other MRI functional applications. In this work, an optimized Open-Face birdcage head coil were designed based on EM simulations. The transmit efficiency, B1 uniformity, and SAR efficiency of the facial open-window birdcage coil with different configurations and a conventional shielded birdcage coil are compared. Finally, an optimized Open-Face birdcage head coil was built and evaluated on a whole body 5T MRI scanner. |
| 4227 | Computer 142
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A 48-channel head and neck neurovascular coil for MR vessel wall imaging at 5 T |
| Yingchao Tan1,2,3, Qiaoyan Chen1,2, Guangzu Xu3, Lei Zhang1,2, Na Zhang1,2, Xiaoliang Zhang4, Xin Liu1,2, Hairong Zheng1,2, and Ye Li1,2 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, 3Shanghai United Imaging Healthcare, Shanghai, China, 4Department of Biomedical Engineering, State University of New York at Buffalo, New York, NY, United States |
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Keywords: High-Field MRI, Head & Neck/ENT Ultra-high field magnetic resonance imaging (MRI) has been increasing in use for human brain imaging. However, due to the absence of a head and neck neurovascular coil, joint imaging of intracranial and extracranial arterial vessel wall has not been applied in current ultra-high field MRI. In this study, a 48-channel head and neck receiver neurovascular coil for joint imaging of intracranial and extracranial arterial vessel wall at 5T was developed. Simultaneous high-resolution imaging of intracranial and extracranial arterial walls with an isotropic spatial resolution of 0.5 mm has been achieved, which further expands the application of ultra-high field imaging. |
| 4228 | Computer 143
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Automatic Alignment of Ex-vivo Brain Pathology to 7T structural MRI |
| Jinghang Li1, Nadim Farhat1, Jacob P. Berardinelli1, Joseph M. Mettenburg2, Howard J. Aizenstein1,3, Julia K. Kofler4, and Tamer S. Ibrahim1,3 | ||
1Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States, 2Neuroradiology, University of Pittsburgh Medical Center, Pittsburgh, PA, United States, 3Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States, 4Pathology, University of Pittsburgh Medical Center, Pittsburgh, PA, United States |
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Keywords: High-Field MRI, Ex-Vivo Applications In this work, we present an image alignment pipeline that facilitates ongoing Alzheimer’s disease (AD) white matter pathology studies. Following our recently developed ex-vivo 7T cutting-guide container [1], in this work, we demonstrate a standardized alignment (between histopathology and ex-vivo 7T MRI) procedure that significantly reduces human effort and eliminate the need for manual alignment. |
| 4229 | Computer 144
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Improved visualization of whole-brain structures and pathology at ultra-high field 7T MRI with parallel transmission universal pulses |
| Caohui Duan1, Xiangbing Bian1, Kun Cheng1, Song Wang1, Linchang Liu1, Jinhao Lyu1, Jianxun Qu2, Franck Mauconduit3, and Xin Lou1 | ||
1Department of Radiology, Chinese PLA General Hospital, Beijing, China, 2MR Collaboration, Siemens Healthineers Ltd., Beijing, China, 3CEA NeuroSpin, Paris, France |
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Keywords: High-Field MRI, Parallel Transmit & Multiband Ultra-high field 7T MRI provides a significant increase in signal-to-noise ratio and contrast for noninvasively visualizing the brain, but is challenging to use for whole-brain imaging. In this study, we investigated the clinical potential of parallel transmission universal pulses (UP) for improving visualization of whole-brain structures and pathology. Our results show that UP enables remarkable signal contrast improvement throughout the brain, which is promising to improve lesion detection (e.g., brain metastases) and structures visualization over the whole brain. |
| 4230 | Computer 145
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Predictive Value of Intrapixel Incoherent motion (IVIM) Imaging For Prognostic Factors in Breast Cancer |
| Jian-mei Fu1, Jing Chen1, Gui-dong Dai1, and Yun-zhu Wu2 | ||
1The Affiliated Hospital of Southwest Medical University, LUZHOU, China, 2MR Scientific Marketing, Siemens Healthineers Ltd, Shanghai, China |
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Keywords: High-Field MRI, Diffusion/other diffusion imaging techniques, Intravoxel Incoherent MotionImaging The objective of this study was to estimate the true diffusion and motion of molecules in the capillary network using the VIM biexponential model without injection of contrast media, three parameters (d value, d * value and F value) were obtained to evaluate the expression of prognostic molecules (ER, PR, Her-2, Ki-67) in breast cancer, which can guide the treatment of breast cancer more precisely.
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| 4231 | Computer 146
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GRAPPA acceleration of Cartesian magnetic resonance fingerprinting (MRF) at 7T |
| Saba Shirvani1, Belinda Ding2, Iulius Dragonu2, and Christopher T. Rodgers1 | ||
1Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom, 2Research and Collaboration UK, Siemens Healthcare Ltd, Frimley, United Kingdom |
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Keywords: High-Field MRI, MR Fingerprinting, Quantitative Imaging, Tissue Characterization, Brain MR fingerprinting enables for robust simultaneous quantitative parametric mapping and is usually performed with spiral acquisitions. These are particularly sensitive to B1 inhomogeneities and hence more susceptible at ultra high-field. To mitigate B1 inhomogeneity effects, we implemented a Cartesian MRF approach. Cartesian 2D data collection time is somewhat slow, and we overcome this by demonstrating the feasibility of GRAPPA acceleration for applications in phantoms and in vivo. We present a fully sampled Cartesian data set in a phantom and in vivo, and we present the performance of increasing GRAPPA acceleration factors to reduce scan time significantly, without compromising image quality. |
| 4232 | Computer 147
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Effect of conductor width on coil array coupling |
| Yunkun Zhao1 and Xiaoliang Zhang1 | ||
1Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: High-Field MRI, Non-Array RF Coils, Antennas & Waveguides This study investigates the effect of conductor width of the RF coils to the EM coupling of an array. The results show that the wide conductor of the RF coils offers less EM coupling among resonant elements. |
| 4233 | Computer 148
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RF Field Enhancement with Ultrahigh Dielectric Constant Material for Micro Imaging at 7T |
| Mohan Jayatilake1, Christopher T Sica1, Dhevin Karunanayaka1, Anupa Ekanayaka2, Biyar Ahmed1, Rommy Elyan1, and Prasanna Karunanayaka1 | ||
1Pennsylvania State University College of Medicine, Hershey, PA, United States, 2Grodno State medical University, Grodno, Belarus |
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Keywords: High-Field MRI, High-Field MRI In this study, we investigated the effects of ultra-high dielectric constant (uHDC) material for reducing noise and enhancing the B1 efficiency at 300 MHz for 1H nuclear applications at 7T. Using electromagnetic field simulations [CST Studio (2020) software] and imaging experiments, we estimated B1+ efficiency maps for a phantom mouse brain with and without uHDC material. Our results show significant enhancement of B1+ efficiency and Signal-to-Noise ratio (SNR) in the presence of the uHDC material. |
| 4234 | Computer 149
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A wireless unilateral Rx-only RF coil for dedicated MRI of a human breast at 1.5 T |
| Aleksander Fedotov1, Pavel Tikhonov1, Georgiy Solomakha1, Victor Puchnin1, Alena Shchelokova1, and Anna Hurshkainen1 | ||
1Department of Physics, ITMO University, St. Petersburg, Russian Federation |
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Keywords: High-Field MRI, RF Arrays & Systems Wireless dedicated radiofrequency coils have recently proven to be a good alternative to conventional cable-connected coils due to compatibility with the scanners of different vendors. Due to significant increase of B1+ with respect to body coil manual calibration procedure needed often for operation of wireless coils.The goal of this work is to develop the first Rx-only wireless coil for dedicated breast MRI to overcome the aforementioned drawback. For that the passive detuning structure inserted to wireless Helmholtz resonator was designed and studied. |
| 4235 | Computer 150
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Passive shielding design for ultra-high field MRI superconducting magnets using an integral operation with nonlinear iteration |
| Yaohui Wang1, Qiuliang Wang1, Ming Yan1, Weimin Wang2, Zhifeng Chen3, and Feng Liu4 | ||
1Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China, 2School of Electronics & Institute of Biomedical Engineering, Peking University & Shenzhen Graduate School, Beijing, China, 3Monash Biomedical Imaging, Monash University, Melbourne, Australia, 4School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia |
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Keywords: Magnets (B0), Screening, Passive shielding Passive shielding is a feasible approach to constrain the strong magnetic fluxes in ultrahigh field MRI superconducting magnets. However, an in-depth investigation of the passive shielding design is not well discussed in the literature and notably lacks nonlinear optimization design/analysis methods for this practice. This work developed a computation algorithm for passive shielding design, which uses an integral operation with nonlinear iteration. An exemplification for shielding a 9.4T whole-body MRI superconducting magnet showed the significant advantages of the proposed method over commercial packages. The optimized passive shielding scheme will be used in our future magnet engineering projects. |
| 4236 | Computer 151
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Development of Head and C-Spine coils for use at 7T |
| Jagjit Sidhu1, Alexander Smerglia2, Labros Petropoulos2, Tsinghua Zheng2, Xiaoyu Yang2, Jami Tatulinski2, Ken Sakaie1, Paul Taylor 2, and Mark Lowe1 | ||
1Cleveland Clinic, Cleveland, OH, United States, 2Quality Electrodynamics, Mayfield Heights, OH, United States |
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Keywords: High-Field MRI, Spinal Cord MR imaging at 7T provides a greater signal intensity, which yields some combination of a greater signal-to-noise ratio, smaller voxel size, and/or faster scan times compared with lower field strengths. However, there remains room for improvement at 7T in terms of image homogeneity and a limited selection of coils. In this work, we summarize ongoing efforts to develop a single-transmit (STX) cervical spine (C-spine) and a parallel transmit (PTX) head coil. Both coils have a more open design with detachable anterior halves and larger physical dimensions. |
| 4237 | Computer 152
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Lumped inductors in RF resonators decrease the B1 fields in samples at ultrahigh fields |
| Yunkun Zhao1 and Xiaoliang Zhang1 | ||
1Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: High-Field MRI, RF Arrays & Systems This study investigates the effect of lumped inductors used in RF resonant circuits on the magnetic field strength generated by the radiofrequency (RF) coils. The results show that the lumped inductors can reduce B1 fields in samples. |
| 4238 | Computer 153
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Improved Transmit Efficiency and Clinical Coverage using a Cervical Spine Array with a Volumetric Transmitter at 7T |
| Alexander Smerglia1, Labros Petropoulos1, Jami Tatulinski1, Tsinghua Zheng1, Xiaoyu Yang1, Jagjit Sidhu2, Ken Sakaie2, and Mark Lowe2 | ||
1Quality Electrodynamics (QED), Mayfield, OH, United States, 2Imaging Institute, Cleveland Clinic, Cleveland, OH, United States |
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Keywords: High-Field MRI, Brain, Spine, Imaging, Cerebellum Several challenges are present when imaging the cervical spine in high-field MRI, such as achieving B1 coverage over the desired anatomy while maximizing efficiency of the transmitter. A cervical spine array coil with a volume transmit birdcage was built and tested on a system for improved transmit coverage and efficiency over previous prototypes. The coil consists of a partially shielded 22-rung birdcage transmitter and a 24 element receive RF array. A new mechanical design with larger eye windows improves the clinical experience. Improved transmit efficiency and complete B1 field coverage in the cervical spine region were confirmed through volunteer imaging. |
| 4239 | Computer 154
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Comparing the imaging performance of a three-channel endorectal coil for magnetic resonance imaging at 5T and 3T |
| Zhiguang Mo1,2, Xiaoping Zhang3, Huageng Liang3, Changjun Tie1,2, Wen Xiao3, Qi Cao3, Chenchen Liu3, Xiaoliang Zhang4, and Ye Li1,2 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, Shenzhen, China, 3Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China, 4Department of Biomedical Engineering, State University of New York at Buffalo, NY, United States., Buffalo, NY, United Stats, Buffalo, NY, United States |
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Keywords: High-Field MRI, Prostate We made a three-channel endorectal coil for prostate imaging on the 5T magnetic resonance system and compared the imaging performance of the coils with the same structure on the 5T system and the 3T system. Prostate images at resolution of 0.78 mm × 0.78 mm × 2.5 mm were performed. In vivo prostate study shows that the endorectal coil works on the 5T system shows better image quality compared with the endorectal coil and surface coil array on the 3T system. |
| 4240 | Computer 155
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Uniformity Improvement of the 7T Body MR Images |
| Bu S Park1 and Sunder Rajan2 | ||
1FDA, Silver Spring, MD, United States, 2Division of Biomedical Physics (DBP), FDA, Silver Spring, MD, United States |
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Keywords: High-Field MRI, Electromagnetic Tissue Properties To optimize MR image quality of 7T Body, the image region is divided into multiple ROIs, which can be independently optimized using transmit array optimization techniques to improve image intensity. Compared to the results of quadrature driving method, mean and SD of |Mt| in the full image (inner diameter of 500 mm) were improved 47% (Mean) and 48% (SD), whereas 94% (Max) and 97% (Mean) improved in the unaveraged SAR using the proposed method. The proposed method using multiple independently optimized ROIs and numerical simulations significantly improved uniformity of |Mt| body images at 7T. Keywords: 7T Body, Uniformity, SAR |
| 4241 | Computer 156
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Towards high sensitivity 13C MRS of Human Brain Glycogen at 7T |
| Eulalia Serés Roig1 | ||
1Laboratory of Functional and Metabolic Imaging (LIFMET), Institute of Physics (IPHYS), School of Basic Sciences (SB), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland |
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Keywords: Phantoms, Non-Proton Largely neglected due to its low concentration, yet brain glycogen plays an active role in brain energy metabolism and may be involved in a variety of brain diseases. The application of 13C MRS along with 13C-glucose intravenous infusion is to date the forefront method for investigating brain glycogen metabolism in vivo. Notably, the C1-resonances of glycogen and glucose have been detected non-invasively in the conscious human brain by 13C MRS at 4T after 13C-glucose infusion labelled at the C1-carbon. In this study, we explore the potential of 13C MRS at 7T with broadband 1H-decoupling towards measuring glycogen and glucose C1-resonances. |
| 4242 | Computer 157
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FAIR Benchmarking of 7T MRI Antennas – Case for a Standardized Protocol for RF Transmit Element Performance Assessment |
| Max Joris Hubmann1,2, Bilguun Nurzed3, Thoralf Niendorf3, Oliver Speck2,4, and Holger Maune2 | ||
1Siemens Healthineers GmbH, Magdeburg, Germany, 2Otto-von-Guericke University, Magdeburg, Germany, 3Berlin Ultra-High Field Facility, Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, 4Research Campus STIMULATE, Magdeburg, Germany |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides This abstract proposes a standardized setup and four standardized metrics to increase 7T Tx RF antenna concept comparability and reproducibility, with the goal of a better technology transfer of antenna concepts across the MR community. Eight antenna concepts are evaluated based on power and SAR efficiency as well as mutual coupling and reliance on load changes using a rectangular phantom mimicking the average electromagnetic body properties. Based on the presented results, much information can be collected and deductions about each antenna's preferable ambits drawn. In conclusion, this work initiates a first standardized protocol for analyzing Tx RF antenna concepts. |
| 4243 | Computer 158
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End-Grounded Dipole RF Element with Extended Coverage and Minimized SAR at 7T MRI |
| Haiwei Chen1, Lei Guo1, Yang Gao2, Zhiyan Quan3, Xiaocui Tang3, Sihong Pan3, Feng Liu1, and Xiaotong Zhang3 | ||
1the University of Queensland, Brisbane, Australia, 2School of Electronic Engineering (National Key Laboratory of Antennas and Microwave Technology) and Hangzhou Institute of Technology, Xidian University, Hangzhou, China, 3Zhejiang University, Hangzhou, China |
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Keywords: RF Arrays & Systems, RF Arrays & Systems Dipole RF coil suffers from high peak local SAR and limited imaging coverage. In this work, a novel dipole structure is proposed. Compared with the fractionated dipole, the proposed design achieves a substantially enlarged B1 field coverage and more than 25% SAR reduction by generating a uniform surface current on the coil. Experimental validations were conducted and agreed well with the simulation results. |
| 4244 | Computer 159
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Characterization of the RF field for metamaterial-based structures constructed of conducting strips and a dielectric at 7T MRI |
| Santosh Kumar Maurya1 and Rita Schmidt2 | ||
1Brain Sciences, Weizmann Institute of Science, Rehovot, Israel, 2Department of Brain Sciences, Weizmann Institute of Science, Rehovot, Israel |
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Keywords: New Devices, High-Field MRI Metamaterial-based structures constructed of conducting strips and a dielectric have already been used to locally increase the RF transmit field. In this study we characterize the RF field of such structures at 7T MRI. Configurations included either long strips (representing electric dipoles), or a matrix of short strips (representing magnetic dipoles). The RF field dependence on strip density and distribution was analyzed, providing insights useful for efficiency and coverage optimization. The configuration based on a matrix of short strips provides higher RF transmit efficiency, while the use of a non-uniform concave distribution of strips is useful to lower SAR. |
| 4245 | Computer 161
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Inductive and capacitive coupling modes of an RF coil to an ultra-High Dielectric Constant (uHDC) disk resonator |
| Parisa Lotfi1, Soo-Han Soon2, Navid P. Gandji1, Michael Lanagan3, Hannes M. Wiesner2, Xiao-Hong Zhu2, Wei Chen2, and Qing X Yang1 | ||
1Center for NMR Research, Departments of Neurosurgery and Radiology, College of Medicine, Pennsylvania State University, Hershey, PA, United States, 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 3Department of Engineering Science and Mechanics, Pennsylvania State University, State College, PA, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, High-Field MRI, Coil, Dielectric, coupling, SNR We investigated capacitive and inductive couplings of an RF coil to an ultra-High Dielectric Constant (uHDC) disk resonator with a given resonance mode of similar frequency using simulation and experiments. Coupling of the RF coil and uHDC resonator can result in splitting the resonance into two modes: a parallel mode via inductive coupling and an anti-parallel mode via capacitive coupling. With the two resonators, the stronger and deeper penetration of the resultant B1 field is observed with parallel mode (in-phase) than anti-parallel mode (out-of-phase), which supports that the parallel mode is preferable for coupling uHDC resonators for MRI applications. |
| 4246 | Computer 162
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Disentangling coil coupling mechanisms through a Faraday equivalent model: application to the shielded-coaxial-cable (SCC) coil at 7T |
| Giovanni Costa1, Margarethus Maarten Paulides1, and Irena Zivkovic1 | ||
1Department of Electrical Engineering, Technical University of Eindhoven, Eindhoven, Netherlands |
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Keywords: RF Arrays & Systems, High-Field MRI, Coupling, SCC coils, Faraday's law of induction, SAR reduction Minimizing coupling between coils constitutes a major challenge in the design of flexible arrays for UHF MRI. Recently, Shielded-coaxial-cable coils (SCC) were shown to be flexible and intrinsically highly decoupled: however, the decoupling mechanism of SCC remains unclear. In this work, we use an high frequency Faraday-equivalent model of the induced voltage to examine coupling between two SCCs in different geometrical configurations. We show that lower coupling in SCC derives from both lower magnitude of electric and magnetic fields as compared to a loop coil, and we discuss the implications in the design of coils for MRI. |
| 4247 | Computer 163
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Quasi-Static and Time-Generalized Field Computation Methods Compared to the Moment Method for Performance Evaluations of Coil Arrays in PI at UHF |
| Mirsad Mahmutovic1, Sam-Luca JD Hansen1, Manisha Shrestha1, and Boris Keil1 | ||
1Institute of Medical Physics and Radiation Protection, TH Mittelhessen University of Applied Science, Giessen, Germany |
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Keywords: RF Arrays & Systems, Parallel Imaging, Phased Array, Electromagnetic Field Simulations In this study, we compared the quasi-static method (QSM), the time-generalized method (TGM), and the method of moments (MoM) for performance evaluations of coil arrays in parallel imaging (PI) at UHF. We have shown that the QSM and the TGM are a good approximation to the MoM solution, and that all three methods perform similarly in a comparative study with a 64-channel head coil. Furthermore, we could show, that the TGM performs better than the QSM at larger distances in the phantom, which may be beneficial for the evaluation of torso coils. |
| 4248 | Computer 164
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Proof of concept for auto-resonant structure to increase the field of view of surface coils |
| Camille Dubuc1, Clément Thibault2,3, Faouzi Boussaha4, Sina Marhabaie5, Jean-Christophe Ginefri5, and Marie Poirier-Quinot5 | ||
1Universite Paris-Saclay, ORSAY, France, Metropolitan, 2Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France, 3Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, 4GEPI - Observatoire de Paris (CNRS 8111), Université PSL, Paris, France, 5Université Paris-Saclay, BioMaps, ORSAY, France |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Multi Loop Transmission Line Resonator To improve the performances of High Temperature Superconducting surface coils, it is essential to enlarge their field of view while keeping the sample-induced noise low. New multi-loop designs could help meeting this challenge. In this work, we present a preliminary study on a copper coil. We first introduce the design, electromagnetic simulations, realization of a multi-loop transmission line resonator copper coil and experimental characterizations. Signal to Noise Ratio-maps of the coil are then acquired in a 3T field. |
| 4249 | Computer 165
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Impacts of Longitudinal Coil Encoding on Simultaneous Multi-Slice (SMS) Head MRI |
| Yunsuo Duan1,2, Feng Liu1,2, Rachel Marsh1,2, Mathhew Riddle1,2, Gaurav Patel1,2, Alayar Kangarlu1,2, Lawrence S. Kegeles1,2, and John Thomas Vaughan Jr.3 | ||
1Division of Translational Imaging, Department of Psychiatry, Columbia University, New York, NY, United States, 2MRI Research Center, New York State Psychiatric Institute, New York, NY, United States, 3Columbia MR Research Center, Columbia University, New York, NY, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems Coil encoding in the longitudinal direction (z-direction) plays an important role in SMS MRI quality. Although many head coil arrays have been reported, systematic research on impacts of coil encoding in the longitudinal direction on SMS imaging remains insufficient. We present a comparison study of coil encoding for head arrays. Our experimental results showed that, to achieve quality images, the mulitband factor should be equal to or less than the number of coil rows. In extreme cases, the mulitband factor should not exceed 1.5 times the number of coil rows. |
| 4250 | Computer 166
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SNR Visualization: A Toolbox for Locating Flexible Coil Arrays |
| Pulkit Malik1, Tracy Wynn1, Peter Fischer1, and Gillian Haemer1 | ||
1InkSpace Imaging, Pleasanton, CA, United States |
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Keywords: RF Arrays & Systems, Data Analysis, Receive Array SNR We present a MATLAB based visualization toolbox for locating coil elements and evaluating SNR for flexible coil arrays. The greater variation in coil positioning creates challenges for SNR comparisons. By locating coils with coil sensitivity isocontours, the SNR of individual channels can be evaluated while the coil array is flexed. This is used to examine the repeatability of placement, and changes to coil coupling in the different placements. The coil locations can be validated using the SNR visualization displayed as slices, lines, and probe points. Expectations of the SNR field shape are used to further optimize coil locations. |
| 4251 | Computer 167
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MATCHING CIRCUIT CO-SIMULATION FOR MR RADIOFREQUENCY COIL SYSTEM OPTIMIZATION |
| Amer Ajanovic1, Stephen Ogier2,3, Raphael Tomi-Tricot1,4,5, Joseph V Hajnal1,4, and Shaihan Malik1,4 | ||
1Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, LONDON, United Kingdom, 2National Institute of Standards and Technology, Boulder, CO, United States, 3Department of Physics, University of Colorado, Boulder, CO, United States, 4London Collaborative Ultra high field System (LoCUS), London, United Kingdom, 5MR Research Collaborations, SIEMENS Healthcare Limited, Frimley, United Kingdom |
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Keywords: RF Arrays & Systems, Simulations, RF Pulse Design and Fields, parallel transmit coils We present a full closed form solution focusing on S-parameters to achieve tuning and matching of the coils by extending the circuit co-simulation (CCS) by enabling introduction of arbitrary matching networks into the CCS without requiring full RF simulation of the network. We validate the method against CCS and demonstrate its applicability to evaluate full-field solutions for 5 different coil model using MARIE. |
| 4252 | Computer 168
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8kw non-magnetic RF power amplifier with four-way combiner for 5T MRI |
| Jiasheng Wang1,2,3, Shengping Liu3, Jifeng Chen1,2, Xinwei Rong1,2, Xiaoliang Zhang4, and Ye Li1,2 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, 3Chongoing Universit of Technology, Chongqing, China, 4Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems, RF power amplifier Ultra-high-field magnetic resonance requires higher power capability and transmission efficiency. An 8 kW non-magnetic RF power amplifier with four-way combiner for 5T MRI is presented. The whole module adopts non-magnetization design to improve transmission efficiency, and the power of four MOSFETs is combined by a combiner with adjustable balance to meet the output power of 8 kW. |
| 4253 | Computer 169
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A screen-printed and electroplated 4-channel receiver array coil for veterinary imaging |
| Camila Pereira Sousa1,2, Tony Gerges2, Florent Dimeglio1, Jean-Lynce Gnanago2, Valernst Martial Gilmus2, Philippe Lombard2, Hugo Dorez1, Michel Cabrera2, and Simon Auguste Lambert 2 | ||
1Hawkcell, Marcy l'étoile, France, 2Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale de Lyon, CNRS, Ampère UMR5005, Villeurbanne, France |
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Keywords: RF Arrays & Systems, RF Arrays & Systems, Animals In this work, we present a 4-channel receiver array entirely dedicated to veterinary imaging. For this purpose, we have fabricated an array coil on a flexible substrate using silver-ink screen printed process and copper electroplating. This flexible and conformable array coil has the potential to improve veterinary diagnosis with small form-fitting elements that allow a better signal to noise ratio performance. |
| 4254 | Computer 170
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Determination of the Optimum Permittivity of High-Permittivity Pads when Dipoles are Used as Transmit Coils for the Chest |
| Giuseppe Carluccio1,2 and Christopher Michael Collins1,2 | ||
1Radiology, NYU Grossman School of Medicine, New York, NY, United States, 2Center for Advanced Imaging Innovation and Research (CAI2R), New York University, New York, NY, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems, High-Permittivity Materials High-Permittivity Materials are often used to manipulate the radiofrequency field B1. Optimization of the permittivity depends on the geometry of the pad, of the subject and of the coil. In this work we determine the permittivity of two pads positioned around the torso, having thickness 1.5 cm and 3 cm, when a dipole array is used to provide the highest transmit efficiency in the heart. The pads provide an improvement of the transmit efficiency of 9.5% and 7.6% for the 1.5 cm and 3cm case respectively, while providing a SAR reduction of 20.2% and 12.5%. |
| 4255 | Computer 171
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Performance and B1 Efficiency Analysis of Different Dipole Antenna Types at 7T. |
| Aditya Ashok Bhosale 1 and Xiaoliang Zhang1 | ||
1Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Simulations In this work, we compare the performance of several dipole antenna types for MR applications at 7T in terms of quality factor, B1+ strength, SAR, B1+ field pattern, and B1+ efficiency. This study may provide guidance on the selection of an appropriate dipole coil for a specific imaging application. |
| 4256 | Computer 172
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Numerical investigation of multi-turn wireless RF coil for MRI |
| Ming Lu1, Xiaoyang Zhang1, and Xinqiang Yan2,3 | ||
1College of Nuclear Equipment and Nuclear Engineering, Yantai University, Yantai, China, 2Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, 3Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, RF Pulse Design & Fields Standard RF coils require preamplifier models, baluns, coil plugs, and coil ID circuits, which makes coils bulky and expensive. A more affordable way to achieve as high SNR as the standard local receive coil is using the inductively coupled wireless coil. In this work, we numerically investigate whether the multi-turn wireless coil with a similar structure as the stacked coil can enhance the SNR. |
| 4257 | Computer 173
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A Systematic Comparison of Different Dipole Antenna Array Configurations for Knee Imaging Applications at 7T. |
| Aditya Ashok Bhosale 1, Leslie Ying1, and Xiaoliang Zhang1 | ||
1Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: MSK, RF Arrays & Systems In this study, we investigate different multi-channel array configurations formed by various dipole antenna types and compare the array configurations in B1+ field maps, SAR maps, and inter-element isolation for knee imaging at the ultrahigh field of 7T. |
| 4258 | Computer 174
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SNR Improvement with Ultrahigh Dielectric Constant (uHDC) Material for 7T 1H MRS Imaging |
| Mohan Jayatilake1, Christopher T Sica1, Dhevin Karunanayaka1, Anupa Ekanayaka2, Biyar Ahmed1, Rommy Elyan1, and Prasanna Karunanayaka1 | ||
1Pennsylvania State University College of Medicine, Hershey, PA, United States, 2Grodno State medical University, Grodno, Belarus |
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Keywords: High-Field MRI, Challenges We investigated the effects of ultra-high dielectric constant (uHDC) materials for enhancing the B1 field at 300 MHz for potential MRS imaging 1H at 7.0 T. The uHDC material was able to increase the transmit efficiency. We calculated B1+ and B1+ efficiency for a phantom mouse brain with and without uHDC material and empirically obtained nominal flip angle maps and 1H metabolic spectra with and without uHDC. Our results show significant enhancement of Signal-to-Noise ratios (SNRs) of 1H spectra in the presence of the uHDC material. |
| 4259 | Computer 175
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In-bore Reclinable Array for Pediatric Spine Imaging |
| Charbel Matta1, Milica Popović1, and Reza Farivar2 | ||
1Electrical and Computer Engineering, McGill University, Montréal, QC, Canada, 2Ophthalmology, McGill University, Montréal, QC, Canada |
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Keywords: RF Arrays & Systems, RF Arrays & Systems We constructed and tested a reclinable MR compatible chair equipped with an 8-channel spine array coil for 3T. The coil used a combination of overlap and transformer decoupling to maximize spatial resolution without modifying individual coil size. The signal to noise ratio and noise correlation matrices were used to compare the performance of the array to a 32-channel commercial array of the same type. The SNR variations were tested with respect to the inclination of the chair. |
| 4260 | Computer 176
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RF Interference Removal in Multi-Channel Receive coil |
| Harsh Kumar Agarwal1 and Ramesh Venkateshan1 | ||
1GE Healthcare, Bangalore, India |
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Keywords: System Imperfections: Measurement & Correction, Artifacts RF Interference can severely degrade the performance of an MR system. Several solutions such as RF shielding, waveguides and special filters are used to send and receive data to the MRI scanner. These solutions constitute significant part of MR installation and maintenance cost. RF interference in multi-channel receive MR system is strongly correlated across multiple receive channels. This correlation is exploited in this manuscript to remove/suppress the artifacts in the MR images arising due to RF interference. Initials results are demonstrated on 1.5T commercial MRI scanner with data acquired with open RF cage door. |
| 4261 | Computer 177
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Simulations of an integrated RF/wireless neonatal head coil array for multiple-input multiple-output (MIMO) wireless MRI data transmission |
| Olivia Jo Dickinson 1,2, Victor Taracila 3, Devon Karl Overson 1,2, Spencer R Lynch 1,2, Beth Reed1,2, Fraser Robb3, Allen Song1,2, Trong-Kha Truong 1,2, and Dean Darnell 1,2 | ||
1Medical Physics Graduate Program, Duke University, Durham, NC, United States, 2Brain Imaging Analysis Center, Duke University, Durham, NC, United States, 3GE Healthcare, Aurora, OH, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, RF Arrays & Systems, WIFI, wireless, neonatal Neonatal neuroimaging can be significantly improved using a form-fitting, lightweight coil array that is untethered from the scanner for a high SNR and reduced setup time. An iRFW coil array does this by performing simultaneous RF signal acquisition and wireless data transfer with the same coil element. Proof-of-concept simulations of a form-fitting soccer-ball geometry 16-channel iRFW coil head array show a high and uniform SNR in the neonatal head and WIFI 6 antenna gain patterns that radiate power outside the bore using a 2x1 multiple-input multiple-output WIFI 6 scheme for the high data rate wireless transmission of MRI data. |
| 4262 | Computer 178
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A 3T Coil Array for Improved Quantitative Susceptibility Mapping at Multiple Orientations in ex vivo Primate Brains |
| Chaimaa Chemlali1, Dimitrios G. Gkotsoulias2, Alina Scholz1, Sam-Luca JD Hansen1, Torsten Schlumm2, Roland Müller2, Carsten Jäger2, Harald E. Möller2,3, and Boris Keil1 | ||
1Institute of Medical Physics and Radiation Protection, TH Mittelhessen University of Applied Sciences, Giessen, Germany, 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 3Felix Bloch Institute for Solid State Physics, Leipzig University, Felix Bloch Institute for Solid State Physics, Leipzig, Germany |
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Keywords: RF Arrays & Systems, Quantitative Susceptibility mapping Quantitative susceptibility mapping (QSM) with multiple object orientations is typically limited by an appropriate examination time that is appropriate for human subjects and the small range of possible rotation angles within an MRI head coil. Ex vivo QSM can overcome these limitations supporting long acquisition times and the ability to rotate the ex vivo specimen to any position. Therefore, a 3T 26-channel ex-vivo brain array coil was developed for fixed chimpanzee brains. The coil was characterized with bench and image metrics and provides increased reception sensitivity, making it well-suited for high-resolution QSM ex vivo MRI studies. |
| 4382 | Computer 121
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Dephased bSSFP for the Delineation of Interventional Devices |
| Jonas Frederik Faust1,2, Peter Speier1, Axel Joachim Krafft1, Sunil Patil3, Mark E. Ladd2,4, and Florian Maier1 | ||
1Siemens Healthcare GmbH, Erlangen, Germany, 2Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany, 3Siemens Medical Solutions USA Inc., Malvern, PA, United States, 4German Cancer Research Center (DKFZ), Heidelberg, Germany |
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Keywords: Interventional Devices, MR-Guided Interventions Dephased MRI, e.g., used for the delineation of metallic interventional devices, is the reconstruction of images from a shifted k-space and can be achieved by introducing additional “White-Marker” magnetic field gradient moments into the acquisition scheme. A prototype 3D radial sequence was implemented to analyze and compare the artifact of a biopsy needle in a gel phantom for dephased GRE and dephased bSSFP contrast. We found dephased bSSFP to show improved artifact symmetry in comparison with dephased GRE. Undesired signal attributed to fat tissue interfaces in an ex-vivo phantom was successfully suppressed by introducing an altered bSSFP phase cycling. |
| 4383 | Computer 122
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Susceptibility-based Positive Contrast Imaging of MR Compatible Metallic Devices Using Model-based Deep Learning |
| Caiyun Shi1,2, Jing Cheng1, Xin Liu1, Hairong Zheng1, Yanjie Zhu1, Dong Liang1,3, and Haifeng Wang1 | ||
1Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, Shenzhen, China, 2Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Shenzhen, China, Shenzhen, China, 3Research Centre for Medical AI, Shenzhen Institutes of Advanced Technology, Chinese Academy of Science, Shenzhen, China, Shenzhen, China |
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Keywords: Interventional Devices, Machine Learning/Artificial Intelligence Susceptibility-based positive contrast MR imaging exhibits excellent efficacy for visualizing the MR compatible metallic devices, by taking advantage of their high magnetic susceptibility. In this work, a model-based deep learning architecture with U-net is developed to realize the 3D susceptibility-based positive contrast MR imaging on real phantom experiments. We train the network on synthetic data to generate positive contrast images from magnetic field maps for localizing the seeds from their surroundings and demonstrate the potential of the deep learning implementation. |
| 4384 | Computer 123
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Passive Device Tracking for interventional MRI with Ferric Ion Chelated Natural Melanin Nanoparticles |
| Engin Baysoy1, Gizem Kaleli-Can2, Alpay Özcan3, and Chunlei Liu4 | ||
1Department of Electrical Engineering and Computer Sciences, UC Berkeley, BERKELEY, CA, United States, 2Department of Biomedical Engineering, İzmir Demokrasi University, İzmir, Turkey, 3Department of Electrical and Electronics Engineering, Boğaziçi University, İstanbul, Turkey, 4Department of Electrical Engineering and Computer Sciences, UC Berkeley, Berkeley, CA, United States |
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Keywords: Interventional Devices, MR-Guided Interventions, Passive Tracking, Melanin Nanoparticles, MRI devices, interventional MRI Natural melanin nanoparticles (MNPs) labeled with paramagnetic ions provide a potential MRI contrast enhancing material alternative to current MRI contrast agents due to their biocompatibility, biodegradability, metal, and biomolecule chelation properties. In this study, we investigated T1 shortening effect of Fe3+ chelated MNPs solution compared to gadolinium-based contrast agents under 3T MRI. Then, we examined traceability of MNP-Fe3+ ions deposited interventional nitinol guidewire in MR scans. Results clearly showed that the coating of Fe3+ chelated MNPs over the surface of MRI compatible instruments will increase traceability of interventional devices in MRI. |
| 4385 | Computer 124
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Performance of a rotatable Tx/Rx body coil for MR-guided particle therapy |
| Kilian A. Dietrich1,2,3,4, Sebastian Klüter2,5,6, Jürgen Debus2,3,4,5,6,7,8,9,10, Mark E. Ladd1,3,9, and Tanja Platt1,2,4 | ||
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany, 3Faculty of Physics, Heidelberg University, Heidelberg, Germany, 4Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 5National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany, 6Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany, 7National Center for Tumor Diseases (NCT), Heidelberg, Germany, 8German Cancer Consortium (DKTK), Heidelberg, Germany, 9Faculty of Medicine, Heidelberg University, Heidelberg, Germany, 10Department of Radiation Oncology, Heidelberg Ion-Beam Therapy Center (HIT), Heidelberg, Germany |
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Keywords: Interventional Devices, MR-Guided Interventions, Particle therapy Electromagnetic field simulations were performed at 1.5T to characterize the imaging capabilities of an RF body coil that is compatible with MR-guided radiotherapy and that can be rotated to achieve a flexible coil to fixed beam orientation. Transmit and receive field characteristics of the RF coil were calculated inside a phantom, and the homogeneity and power efficiency were analyzed for 24 different angles of rotation. |
| 4386 | Computer 125
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Simulation of the Electric Transfer Function of Partially Inserted Guidewires |
| Felipe Godinez1, Özlem Ipek2,3, Jeffrey Hand2,3, Fatima Ben Haj4, Joseph V Hajnal2,3, and Shaihan J Malik2,3 | ||
1University of California Davis, Sacramento, CA, United States, 2School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 3Centre for the Developing Brain, King's College London, London, United Kingdom, 4Davis Senior High School, Davis, CA, United States |
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Keywords: Interventional Devices, Safety Endovascular interventional devices can heat when used in an MRI system. The heating mechanism can be evaluated using the electric transfer function. In this work we evaluated the TF for a partially inserted guidewire as used in practice, at frequencies corresponding to 0.55T, 1.5T, and 3T. The study revealed that the transfer function varies dramatically with insertion depth for some frequencies and not others. |
| 4387 | Computer 126
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Advanced RF antenna arrangements to improve the efficacy of Thermal Magnetic Resonance of Glioblastoma Multiforme at 7.0T, 9.4Tand 10.5T |
| Nandita Saha1,2, Andre Kuehne3, Jason M. Millward1, and Thoralf Niendorf1,4 | ||
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, 2The Charité – Universitätsmedizin, Berlin, Germany, 3MT MedTech Engineering GmbH, Berlin, Germany, 4Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany |
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Keywords: Interventional Devices, MR-Guided Interventions, Thermal MR This work proposes the concept of four RF applicators combining SGBT dipole and loop building block antenna array for diagnostic proton (1H) imaging and thermal intervention at 7.0T, 9.4T and 10.5T. We demonstrated the relationship between spatial arrangement of the antennas in RF applicator and the SAR profile which further related to temperature rise for targeted thermal intervention of deep-seated brain tumors. This approach of design, simulation, optimization of EM power deposition followed by calculation of the resulting temperature distribution can be adapted as a pre-routine to conduct optimization result for individual patient for further treatment planning. |
| 4388 | Computer 127
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High permittivity material for catheter tracking in interventional imaging |
| Yunkun Zhao1 and Xiaoliang Zhang1 | ||
1Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: Interventional Devices, MR-Guided Interventions This study presents a technique of using high permittivity dielectric materials for catheter tracking in interventional endovascular imaging procedures. The design includes a high dielectric material cylinder at the tip of the catheter. Given the small size and limited space of the catheters, it is challenging to implement the current catheter tracking techniques. In the proposed approach, the high permittivity material mounted on tip of the catheter can amplify the local magnetic fields and makes the catheter tip visible. This method doesn’t need any feeding cables and is not sensitive to the frequency shift which makes it easy to implement. |
| 4389 | Computer 128
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Design of a well decoupled 4-channel catheter Radio Frequency coil array for endovascular MR imaging at 3T |
| KOMLAN PAYNE1, Yunkun Zhao1, Leslie Lei Ying1, and Xiaoliang Zhang1 | ||
1Department of Biomedical Engineering, University at Buffalo, Buffalo, NY, United States |
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Keywords: Interventional Devices, Blood vessels Catheter-based radio frequency (RF) coils for interventional MRI are proposed as a means of obtaining high resolution images with significant advantages over conventional external signal detecting RF coils. A 4-channel catheter array coil was designed to improve the power transmission and SNR using parallel imaging and ultra-sensitive imaging with maximum proximity inside a blood vessel phantom. This design can be scaled to smaller/larger form to fit in tiny/wide vascular structure to provide the required B1 fields and sufficient decoupling among the resonant elements. Numerical simulation was employed to validate the performance and the feasibility of the proposed design. |
| 4390 | Computer 129
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Development and Evaluation of an MR-visible Interventional Microcatheter |
| Bridget F Kilbride1, Teri Moore1, Alastair J Martin1, Mark W Wilson1, and Steven W Hetts1 | ||
1Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States |
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Keywords: Interventional Devices, Interventional Devices Intra-arterial chemotherapy following blood-brain barrier opening (BBBO) can be a highly effective therapeutic delivery mechanism when treating primary and metastatic disease in the brain. Osmotic blood-brain barrier disruption has long been performed under x-ray guidance but has yet to gain clinical traction partially due to outcome variability. MRI is advantageous for its superior soft tissue contrast and real-time perfusion territory validation. We propose a passive microcatheter to provide real-time feedback of catheter positioning during BBBO under MRI guidance. In a phantom, we quantitated susceptibility artifacts at 3T. The catheter showed promise as a new MRI-visible tool to enhance BBBO procedures. |
| 4391 | Computer 130
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Initial experiences assessing the impact of different materials for needle-based interventional devices using advanced DWI and MR thermometry |
| James H Holmes1,2,3, Collin J Buelo4,5, Ruiqi Geng4,5, Matthew R Tarasek6, Desmond TB Yeo6, Christopher L Brace5,7, Diego Hernando5,7,8, Aaron Faacks5, Jia Xu1, Francisco Donato Jr.1, and Shane A Wells5,9 | ||
1Radiology, University of Iowa, Iowa City, IA, United States, 2Biomedical Engineering, University of Iowa, Iowa City, IA, United States, 3Holden Cancer Center, University of Iowa, Iowa City, IA, United States, 4Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, 5Radiology, University of Wisconsin-Madison, Madison, WI, United States, 6GE Research, Niskayuna, NY, United States, 7Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States, 8Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, United States, 9Urology, University of Wisconsin-Madison, Madison, WI, United States |
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Keywords: Interventional Devices, MR-Guided Interventions In this work we report initial results evaluating the imaging artifacts associated with different candidate materials for use in needle-based interventions. The impact of each material was assessed using MRT and DWI ADC as well as compared with local Bo field maps. |
| 4392 | Computer 131
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Electric Dipole Based Metasurfaces Enhance Targeted RF Power Deposition of Thermal Magnetic Resonance at 7.0T, 9.4T and 10.5T |
| Nandita Saha1,2, Rita Schmidt3, and Thoralf Niendorf1,4 | ||
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, Berlin, Germany, 2The Charité – Universitätsmedizin, Berlin, Germany, 3Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel, 4Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany |
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Keywords: Interventional Devices, RF Arrays & Systems, Metamaterial surface This work proposes the feasibility of passive metasurface (MS) to enhance the RF power deposition for Thermal Magnetic Resonance based treatment of brain tumors. An 8 channel hybrid RF applicator combining dipole antenna and passive MS is designed and evaluated at 7.0 T (300 MHz), 9.4 T (400 MHz) and 10.5 T (450 MHz). MS with metal strips inside waterbolus was designed which generates expected resonant modes of the thermal intervention frequency. The result demonstrated use of passive metamaterial surface in RF applicator enhances the RF power deposition inside target volume for targeted RF heating of deep seated brain tumor. |
| 4393 | Computer 132
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Self-activatable photodynamic-immunotherapy based on poly(thioketal) conjugated with photosensitizers |
| Wang Nianhua 1, Yao wang1, and Jiang Xinqing1 | ||
1Guangzhou First People’s Hospital, Guangzhou, China |
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Keywords: Multimodal, Molecular Imaging, MRI Near Infrared Ray Photodynamic therapy is a non-invasive and controllable modality with potential as a novel cancer treatment strategy. However, the ROS production efficiency of PDT is restricted to hydrophobic characteristics and aggregation caused quenching of PSs. Herein, we designed a ROS self-activatable polymer (PTKPa) to suppress photosensitizers ACQ and elevate ROS production capacity. This platform shows therapeutic outcomes in both cells and orthotopic mouse model, which can significantly elevate the intracellular ROS level upon 660nm laser irradiation, induce immunogenic cell death (ICD) to activate antitumor immunity. This work provides a general strategy enhancing tumor photodynamic therapeutic effects. |
| 4394 | Computer 133
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Implementation of Proposed Methods for MR-Guided Transperineal Prostate Interventions: Real Time Trajectory Calculation and Monitoring |
| Thomas Lilieholm1, David A Woodrum2, Walter F Block1,3,4, and Erica M Knavel Koepsel3 | ||
1Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, 2Radiology, Mayo Clinic, Rochester, MN, United States, 3Radiology, University of Wisconsin - Madison, Madison, WI, United States, 4Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, United States |
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Keywords: Interventional Devices, Visualization Utilizing MR guidance for minimally-invasive prostate interventions is known to improve the precision and accuracy of the procedure. Previous work has been done to develop and propose an integrated platform for conveniently providing this image guidance to clinicians for use with transperineal prostate interventions. Since then, the proposed methodology has been applied, in a limited capacity, to assist in an in-vivo prostate biopsy. It was found that the trajectory computation component of the platform was able to accurately guide needle placement to the clinician-selected anatomical regions with little need for correction. |
| 4395 | Computer 134
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Manganese-Phenolic Networks Platform Amplifying STING Pathway Activation for MRI Imaging Guided Cancer Chemo- /Immune Therapy |
| Xinrui Pang1, Ruili Wei1, Ye Wang1, Fangrong Liang1, and Ruimeng Yang1 | ||
1Department of Radiology, Guangzhou First People’s Hospital, GuangZhou, China |
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Keywords: Whole Body, Cancer, Immunity therapy Low immune infiltrates severely hinder cancer immunotherapy. Hence, we developed a manganese-phenolic networks platform (TMPD) The TMPD was based on doxorubicin (DOX) loaded PEG-PLGA nanoparticles and further coated with manganese (Mn)-tannic acid (TA) networks. Mechanistically, DOX could kill cancer cells while Mn2+ could significantly increase the activity of STING pathway related protein to amplify the STING signal and has the function of MRI T1 imaging. The nanoplatform could promote the presentation of tumor antigens and activate a robust innate and adaptive immunity, providing reference for the application of molecular imaging in tumor diagnosis and treatment. |
| 4396 | Computer 135
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PET-MRI lymph node analysis, a predictive tool for recurrence in upper aerodigestive tract cancers |
| Nadya Pyatigorskaya1, Yoann Sclover2, Aurelie Kas2, Lydia Yahia-Cherif1, and Melika Sahli Amor 2 | ||
1ICM, Paris, France, 2APHP, Pitié Salpêtrière, Paris, France |
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Keywords: PET/MR, Head & Neck/ENT, ENT, head and neck, PET/MRI, lymph nodes The aim of our study was to analyze the imaging characteristics of lymph nodes on pre-operative PET-MRI to find the predictors of recurrence or progression.273 patients with ATD cancer who underwent PET-MRI were included. Lymph node PET/MR analysis has shown that the strongest predictors of the recurrence were lymph node enhancement and SUVmax for the controlateral nodes and enhancement, SUVmax node shape for the homolateral nodes. In conclusion, PET-MRI can be an interesting tool in the pre-therapeutic assessment of primary tumors of the ADT with lymph node extension, particularly in the identification of predictive characteristics of recurrence or progression. |
| 4397 | Computer 136
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MRI compatibility study of a brain PET insert integrated with a quadrature birdcage transmit /47-channel receiver head coil assembly at 3 T |
| Qiaoyan Chen1,2, Zhonghua Kuang1,2, Yongfeng Yang1,2, Changjun Tie3,4,5, Xiaoliang Zhang6, Xin Liu1,2, Hairong Zheng1,2, and Ye Li1,2 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, 3Institute of Computing Technology, Chinese Academy of Sciences, Beijing, China, 4University of Chinese Academy of Sciences, Beijing, China, 5Peng Cheng Laboratory, Shenzhen, China, 6Department of Biomedical Engineering, State University of New York at Buffalo, New York, NY, United States |
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Keywords: PET/MR, PET/MR Simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) shows advantages in clinical and research applications for human brain. In this work, MRI compatibility of a brain PET insert integrated with a quadrature birdcage transmit /47-channel receiver head coil assembly was studied. The results of RF field (B1+) distribution, signal-to-noise ratio (SNR) and static field inhomogeneity (ΔB0) show MRI compatibility of the brain PET insert. Simultaneous PET/MRI was implemented, which demonstrated a high performance of the brain PET/MRI system. |
| 4398 | Computer 137
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3D Printed Alignment Apparatus for Retrofitted Rodent PET-MRI at 9.4 Tesla |
| Leo Marecki1, Suyog Pol1, Robert Zivadinov1,2, and Ferdinand Schweser1,2 | ||
1Buffalo Neuroimaging Analysis Center, Department of Neurology at the Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, The State University of New York, Buffalo, NY, United States, 2Center for Biomedical Imaging, Clinical and Translational Science Institute, University at Buffalo, The State University of New York, Buffalo, NY, United States |
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Keywords: PET/MR, Preclinical We developed a retrofitted alignment apparatus that attaches to the MRI’s motor-driven automated positioning system and enables simultaneous preclinical PET/MRI at 9.4T with a stand-alone microPET ring. The system leverages 3D printing technology to achieve stable alignment between the two modalities, consistent placement of animals, and rapid reconfiguration between PET-MRI and MRI-only experiments. Thereby addressing the shortcomings of other retrofitted designs and proving simultaneous PET-MRI capabilities at a reduced cost. |
| 4399 | Computer 138
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Evaluation of MRI performance and PET compatibility of a 32 channel coil for the Siemens Biograph mMR PET/MRI scanner |
| Harris Bidaman1, Katie Dinelle1, Reggie Taylor2,3, and Lauri Tuominen2,4 | ||
1Brain Imaging Centre, Royal Ottawa Mental Health Centre, Ottawa, ON, Canada, 2University of Ottawa Institute of Mental Health Research at The Royal, Ottawa, ON, Canada, 3Department of Physics, Carleton University, Ottawa, ON, Canada, 4Department of Psychiatry, University of Ottawa, Ottawa, ON, Canada |
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Keywords: PET/MR, Brain, Coil We evaluate MRI and PET performance of the novel Siemens 32 channel head coil for the Siemens Biograph mMR. Results are compared to the system standard 12 channel coil. MRI performance (SNR) was improved with the 32 channel coil. PET image uniformity was not impacted. ROI analysis of the PET data indicated a 5% underestimation of activity concentration in the 32 channel coil, however this difference was mitigated by the use of an image derived reference region. Any small differences in PET performance introduced by the 32 channel coil are far outweighed by the superior MRI performance of this coil. |
| 4400 | Computer 139
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Development of Small Animal PET-insert Compatible RF Coils for Simultaneous 129Xe MRI/15O2-PET Brain Perfusion Measurements |
| Elise Noelle Woodward1, Heeseung Lim2,3, Ramanpreet Kaur Sembhi1, Matthew S Fox1,2, and Alexei Ouriadov1,4 | ||
1Physics and Astronomy, Western University, London, ON, Canada, 2Lawson Health Research Institute, London, ON, Canada, 3Siemens Healthcare Limited, London, ON, Canada, 42Lawson Health Research Institute, London, ON, Canada |
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Keywords: RF Arrays & Systems, Hyperpolarized MR (Gas) This study aims to present two birdcage radiofrequency (RF) coils for the use of simultaneous hyperpolarized Xenon-129 (129Xe) MRI and 15O2 PET imaging for brain perfusion measurements. Coils were designed for use with a 2.89T Siemens scanner, or 34.05MHz, one using a low pass filter design, and the other a high pass filter design. |
| 4401 | Computer 140
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Direct Detection of Peak-like Magnetic Field Fluctuations using Rotary Excitation (REX) based MRI |
| Petra Albertova1,2, Maximilian Gram1,2, Martin Blaimer3, Magnus Schindelhütte4, Thomas Kampf4, Peter Michael Jakob2, and Peter Nordbeck1,5 | ||
1Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany, 2Experimental Physics 5, University of Würzburg, Würzburg, Germany, 3Fraunhofer Institute for Integrated Circuits IIS, Würzburg, Germany, 4Department of Diagnostic and Interventional Neuroradiology, University Hospital Würzburg, Würzburg, Germany, 5Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg, Würzburg, Germany |
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Keywords: Bioeffects & Magnetic Fields, Pulse Sequence Design, spin-lock With spin-locking, the resonance of the spin system can be shifted adjustably to the low frequency range for detection of biomagnetic field oscillations. In this study, we demonstrate that spin-locking is also sensitive to peak-like magnetic field fluctuations with broader spectral width. Simulations and measurements demonstrate that, in addition to the application of imaging neural oscillations, the spatially resolved detection of biomagnetic peaks is possible. Initial results show a high agreement between simulations and experiments and mark a first step towards spin-lock based diagnostics of biomagnetic activity, e.g. imaging of the cardiac conduction system. |
| 4402 | Computer 141
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Comparison of the Optimization of a 60-channel Transmit Coil in pTx and sTx mode at 7T |
| Andrea N Sajewski1, Tales Santini1, Tiago Martins1, Jacob Berardinelli1, and Tamer Ibrahim1 | ||
1University of Pittsburgh, Pittsburgh, PA, United States |
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Keywords: In Silico, RF Arrays & Systems The recently developed 60-channel Tic-Tac-Toe transmit coil was analyzed for use in either single or parallel transmit systems at 7T. With the 60-channel TTT coil, excellent homogeneity can be achieved and safe levels of SAR can be provided regardless of which system (sTx or pTx) is used. |
| 4403 | Computer 142
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Tailored cost functions for improved static pTX-based B1+ shimming in 7T cardiac MRI. |
| Maxim Terekhov1, David Lohr1, Christoph Aigner2, Sebastian Dietrich2, Sebastian Schmitter2, and Laura M. Schreiber1 | ||
1Chair of Molecular and Cellular Imaging, Comprehensive Heart Failure Center, University Hospital Würzburg, Wuerzburg, Germany, 2Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Berlin, Germany |
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Keywords: Parallel Transmit & Multiband, Cardiovascular Parallel transmit (pTX) technology is an emerging tool for improving of the B1+-field homogeneity in cardiac MRI (cMRI) at the ultra-high magnetic field. In this work, we propose a methodology to enhance the characteristics of the shaped B1+ field using a tailored cost function for the optimization procedure computing complex transmit vectors of magnitudes and phases for driving TX array. Using the cost functions (CF) based on the local B1 gradients with fine-tuning by weighting coefficients allows for considerable improvement of static pTX B1-shimming quality in compared to traditional CF using the coefficient-of-variation (CoV) of B1. |
| 4404 | Computer 143
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Static and dynamic parallel transmission (pTx) for human cardiac MRI at 21.0 T |
| Bilguun Nurzed1, Dennis Hieronymi1, Thomas Wilhelm Eigentler1, Christoph Stefan Aigner2, Sebastian Schmitter2, and Thoralf Niendorf1,3,4 | ||
1Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, 2Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany, 3Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine, Berlin, Germany, 4MRI.TOOLS, Berlin, Germany |
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Keywords: Shims, RF Arrays & Systems, Cardiovascular Transmission field inhomogeneities at ultrahigh and extreme field MRI can be offset using static or dynamic pTx. Responding to the challenges and recognizing the opportunities of cardiac MRI, this abstract examines the feasibility of parallel transmission (pTx) using self-grounded bow-tie (SGBT) RF array configurations for static and dynamic B1+ homogenization of the heart at 21.0T. Our results demonstrate that static pTx provides limited performance at 21.0 T, but dynamic pTx enables uniform heart excitation at 21.0T |
| 4405 | Computer 144
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Comparison of the transmit performance and Local SAR for multi-row parallel transmit coil arrays at 3 Tesla human brain MRI |
| Nejat Karadeniz1, Jo Hajnal1,2, and Özlem Ipek1 | ||
1Biomedical Engineering, King's College London, London, United Kingdom, 2Centre for the Developing Brain, King's College London, London, United Kingdom |
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Keywords: RF Arrays & Systems, Safety MRI multi-row array coils can offer increased flexibility to control and tailor the RF field distribution through RF Shimming. The performance of various multi-row configurations of parallel-transmit (pTx) RF coil array for brain imaging at 3T is investigated using electromagnetic field simulations with digital human computational model for overlapping and non-overlapping loop coil elements in 16- to 24-channel single, double, triple-row arrays. We found that triple-row coil arrays improve the transmit field homogeneity in the entire volume of the head. The double-row coil array offers the best SAR efficiency among other investigated coils. |
| 4406 | Computer 145
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Design of a universal RF-shimming drive mode for head and neck imaging at 7 Tesla using a 16-channel pTx array |
| Ehsan Kazemivalipour1,2, Markus W. May3,4, D. Rangaprakash1,2, Berkin Bilgic1,2,5, Jason P. Stockmann1,2, Robert L. Barry1,2, Boris Keil6,7, Lawrence L. Wald1,2,5, and Bastien Guerin1,2 | ||
1A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany, 4High-Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, 5Harvard-MIT Division of Health Sciences Technology, Cambridge, MA, United States, 6Institute of Medical Physics and Radiation Protection, Department of Life Science Engineering, Mittelhessen University of Applied Sciences, Giessen, Germany, 7Center for Mind, Brain and Behavior (CMBB), Philipps-University Marburg, Marburg, Germany |
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Keywords: RF Pulse Design & Fields, RF Pulse Design & Fields We calculate “universal” RF-shimming excitations that provide maximum B1+ coverage and homogeneity across the brain & c-spine using a patient-friendly 16-channel pTx array. We simulated three body models and three z-positions to ensure robustness to both B1+ and SAR variation across a range of head/neck sizes and shapes (universal design). We provide two solutions, both of which may be saved on the scanner: a low-SAR solution that improves flip-angle uniformity by 13% compared to the BC mode excitation (same SAR) and a high-SAR excitation that improves flip-angle non-uniformity by 25% at the cost of a 2x local SAR increase. |
| 4407 | Computer 146
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Efficient Use of Specific Absorption Rate Limits Through Sub-Population Universal Pulses in Parallel Transmission |
| Igor Tyshchenko1, Simon Lévy2, Jin Jin3, Bahman Tahayori4, and Leigh A. Johnston1 | ||
1Department of Biomedical Engineering, The University of Melbourne, Melbourne, Australia, 2MR Research Collaborations, Siemens Healthcare Pty Ltd, Melbourne, Australia, 3MR Research Collaborations, Siemens Healthcare Pty Ltd, Brisbane, Australia, 4The Florey Institute of Neuroscience and Mental Health, Melbourne, Australia |
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Keywords: Parallel Transmit & Multiband, Parallel Transmit & Multiband, Universal pulses, safety margins, 7T MRI Universal pulse (UP) design in parallel transmit (pTx) imaging is a calibration-free technique that can effectively mitigate the radiofrequency (RF) field inhomogeneity over a population in ultra-high field MRI. In this work, we explore a middle-ground approach of using sub-population UPs. Assuming the entire population is divided into sub-populations by grouping similar anatomical shapes and positions, UPs can thus be designed with reduced intersubject variability. In this preliminary study of head imaging, it is demonstrated that sub-populations of various sizes centred at the mean shape and position can reduce safety margins and improve UP’s performance. |
| 4408 | Computer 147
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Accelerated Volumetric Multi-Channel pTx B1+ Mapping at 7T for the Brain and Heart |
| James L. Kent1, Ladislav Valkovič2,3, Iulius Dragonu4, Mark Chiew1,5,6, and Aaron T. Hess1 | ||
1Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom, 2Oxford Centre for Clinical Magnetic Resonance Research, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom, 3Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia, 4Research & Collaborations GB&I, Siemens Healthcare Ltd, Camberley, United Kingdom, 5Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, 6Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada |
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Keywords: Parallel Transmit & Multiband, Parallel Transmit & Multiband Ultra-high field MRI with parallel transmit offers significant advantages but B1+ maps are required to utilize its potential. Acquiring B1+ maps for each channel is time-consuming and limits the application of ultra-high field in clinical practice. In this abstract we present an approach to acquire full 3D multi-channel B1+ maps in 11 seconds. We do this by employing a time-interleaved acquisition of modes strategy using undersampled relative maps and two fast undersampled Sandwich B1+ maps all reconstructed using TxLR, a calibrationless reconstruction for transmit field maps. We demonstrate this approach with simulations and scans in phantom and in the brain. |
| 4409 | Computer 148
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An 8-Parallel Transmit 32-Receive Array Head Coil for Clinical Use at 7.0 Tesla |
| Alexander Smerglia1, Labros Petropoulos1, Xiaoyu Yang1, Tsinghua Zheng1, Paul Taylor1, Blaise Whitesell1, Jagjit Sidhu2, Ken Sakaie2, and Mark Lowe2 | ||
1Quality Electrodynamics (QED), Mayfield, OH, United States, 2Imaging Institute, Cleveland Clinic, Cleveland, OH, United States |
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Keywords: Parallel Transmit & Multiband, Brain An 8-parallel transmit 32-Rx head coil was built and evaluated for performance in high-field MRI. The coil is comprised of an 8-rung curved degenerate birdcage transmitter and a 32-loop element receive array. The coil housing was designed with an anterior/posterior split and eye windows for patient comfort, and a sizable interior that can fit 99 percent of the general population. A volunteer was imaged to confirm transmit coverage, which includes the entire brain and upper cervical spine. Good B1 uniformity, and improved transmit efficiency over previously built non-curved Tx head coils were also confirmed. |
| 4410 | Computer 149
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Quasi-Damped Newton’s Method for Large Flip Angle Universal Pulse Design Using Parallel Transmission at 9.4T |
| Celik Boga1, Ole Geldschlager2, and Anke Henning1 | ||
1UT Southwestern Medical Center, Dallas, TX, United States, 2Max Planck Institute for Biological Cybernetics, Tuebingen, Germany |
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Keywords: RF Pulse Design & Fields, High-Field MRI The Universal Pulse (UP) concept to parallel transmission radiofrequency (RF) pulse design was introduced to avoid time consuming B1+ and ΔB0 data acquisition before each clinical scan. Introduced large flip angle design methods utilize kT-point trajectories and small tip angle approximation. In this work, new quasi damping scheme for Newton's methods method is introduced for large flip angle universal pulse design using numerical solution of the Bloch equation. Introduced quasi-damping scheme can be utilized in large flip angle Universal Pulse design for all flip angles including 180o pulses, without the loss of performance. |
| 4411 | Computer 150
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Comparing parallel transmit 2-spoke against circularly polarized pulses for 7T whole brain diffusion MRI |
| Minghao Zhang1, Belinda Ding1,2, Iulius Dragonu2, Patrick Liebig3, Robin M. Heidemann3, and Christopher T. Rodgers1 | ||
1Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom, 2Siemens Healthcare Limited, Camberley, United Kingdom, 3Siemens Healthcare GmbH, Erlangen, Germany |
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Keywords: Parallel Transmit & Multiband, Diffusion Tensor Imaging Diffusion MRI (dMRI) is inherently limited by SNR. 7T scans increase intrinsic SNR but suffer from regions of signal dropout, especially in temporal lobes and cerebellum. We applied dynamic parallel transmit (pTx) to allow whole-brain 7T dMRI and scanned 7 volunteers comparing pTx 2-spoke and circularly polarized pulses. PTx 2-spoke scans increased whole-brain mean temporal SNR increased by 22%, produced cleaner fractional anisotropy maps, and reduced fiber estimation uncertainty by 4% (P=0.016) for first fibers and 2% (P<0.001) for second fibers. However, less restrictive SAR limits will be needed for clinical translation of our approach due to long scan time. |
| 4412 | Computer 151
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RF mode switching based Tx coil system for B1+ homogeneity mitigation at 7T: basic concept and preliminary study |
| Shin-ichi Urayama1, Masaki Fukunaga2, and Martijn Cloos3 | ||
1Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan, 2National Institute for Physiological Sciences, Okazaki, Japan, 3University of Queensland, Brisbane, Australia |
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Keywords: RF Arrays & Systems, RF Arrays & Systems, RF-mode, non-pTx To mitigate B1 inhomogeneity problems in ultra-high-field MRI, we proposed RF-mode switching technique which doesn’t need an expensive parallel transmit (pTx) system. As a preliminary study, we developed an RF-switching circuit (one of the main parts of the system) and validated its function through phantom experiments. The results showed that the switching function works well, although a certain degree of power-loss was observed both at bench (< -1dB) and on the images. We have re-designed a new switching circuit and will continue to the development to demonstrate this technique at a fraction of the cost of a pTx system. |
| 4413 | Computer 152
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Optimisation of pulse-specific phase schedule reduces peak RF amplitude in multiband parallel-transmit pulses |
| Belinda Ding1,2, Sydney Nicole Williams1, Minghao Zhang3, Jürgen Herrler4, Patrick Liebig4, Iulius Dragonu5, Radhouene Neji5, Christopher T. Rodgers3, and David A Porter1 | ||
1Imaging Centre of Excellence, University of Glasgow, Glasgow, Scotland, 2Siemens Healthcare Ltd., Glasgow, United Kingdom, 3Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom, 4Siemens Healthcare GmbH, Erlangen, Germany, 5Siemens Healthcare Ltd., London, United Kingdom |
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Keywords: Parallel Transmit & Multiband, Parallel Transmit & Multiband, phase schedule Multiband(MB) imaging can greatly reduce scan time, but MB pulses often encounter peak amplitude constraints. An optimal phase schedule has been published for traditional single-transmit (sTx) RF pulses. However, after an initial evaluation, we found that it only has marginal benefits for parallel-transmit (pTx) pulses. We compared four common optimisation algorithms (fmincon, fminsearch, simmulated annealing, global search) to determine the most suitable algorithm for choosing the best offset phases for a pTx pulse. Overall, fmincon efficiently selected the optimal phase schedule of a pTx pulse and lowered peak amplitude by an average of 15% when MB-factor=3. |
| 4414 | Computer 153
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Slice-specific B1 shimming can improve the repeatability of multi-shot, diffusion-weighted imaging at 7T |
| Belinda Ding1,2, Sydney Nicole Williams1, Iulius Dragonu3, Jürgen Herrler4, Sarah Allwood-Spiers5, Patrick Liebig4, and David A Porter1 | ||
1Imaging Centre of Excellence, University of Glasgow, Glasgow, Scotland, 2Siemens Healthcare Ltd., Glasgow, United Kingdom, 3Siemens Healthcare Ltd., London, United Kingdom, 4Siemens Healthcare GmbH, Erlangen, Germany, 5NHS Greater Clyde and Glasgow, Glasgow, Scotland |
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Keywords: Parallel Transmit & Multiband, Diffusion/other diffusion imaging techniques, high-field, 7T, DWI, repeatability Parallel transmission (pTx) can significantly improve readout-segment EPI (rsEPI) diffusion-weighted imaging (DWI) at 7T when compared to the non-pTx sequence. However, no study has been done to assess the repeatability of pTx-DWI. Thus, we conducted a test-retest study to evaluate the impact pTx pulses have on the repeatability of ADC measures in a rsEPI[DP1] DWI sequence at 7T. Overall, pTx-DWI had higher SNR and can potentially improve the repeatability for intra- and inter-session ADC measures even when different B1-shim coefficients are used for different sessions. This suggests that pTx has an important role in quantittaive imaging studies at 7T. |
| 4415 | Computer 154
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Optimized interferometric encoding of presaturated TurboFLASH B1-mapping for pTx at 7T MRI: Application to T1-mapping in the spinal cord |
| Aurelien Destruel1,2,3, Franck Mauconduit4, Aurélien Massire5, Vincent Gras4, and Virginie Callot1,2,3 | ||
1Aix-Marseille Univ, CNRS, CRMBM, Marseille, France, 2APHM, Hôpital Universitaire Timone, CEMEREM, Marseille, France, 3iLab-Spine, International Associated Laboratory, Montréal, Canada, Marseille, France, 4Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-yvette, France, 5Siemens Healthcare SAS, Saint-Denis, France |
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Keywords: RF Pulse Design & Fields, Spinal Cord One of the best solutions to B1 inhomogeneities observed at ultra-high field MRI is to use parallel transmit techniques (pTx). However, fast and accurate knowledge of the B1+ is required. The presaturated TurboFLASH (satTFL)-based B1-mapping sequence, with interferometric encoding, has shown great promise due to its speed and reliability, but it was observed that its performance may drop when used with unconventional radiofrequency coils and applications. In this study, a novel optimization of the interferometric encoding is presented and applied to cervical spinal cord MRI at 7T. The impact of having improved B1-maps is evaluated on pTx MP2RAGE-based T1-mapping. |
| 4416 | Computer 155
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Multiphoton Parallel Transmission (MP-pTx) |
| John M Drago1,2,3, Bastien Guerin2,3, Stephen F Cauley2,3, and Lawrence L Wald2,3,4 | ||
1Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3A. A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 4Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States |
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Keywords: RF Pulse Design & Fields, Parallel Transmit & Multiband We introduce multiphoton parallel transmission to mitigate nonuniform excitation in high-field MRI. Following an on-resonance birdcage subpulse, a multiphoton subpulse consisting of a single, off-resonance, high-frequency field from a birdcage coil, is supplemented with low-frequency parallel irradiation from a shim array. RF heating concerns are simplified compared to pTx, because only the birdcage coil produces significant SAR. Using a small-tip forward model, we optimize a nonconvex problem to find the amplitudes/phases of the low-frequency coils. Simulations demonstrate flip angle variation reduction across the brain ROI of 31.5% and NRMSE reduction of 42.0% compared to a conventional 7 T birdcage excitation. |
| 4417 | Computer 161
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A Flexible iPRES AIR Coil Array for MRI and Localized B0 Shimming |
| Devon Karl Overson1,2, Dean Darnell1,2, Fraser Robb3, Allen Song1,2, and Trong-Kha Truong1,2 | ||
1Duke-UNC Brain Imaging & Analysis Center, Duke University, Durham, NC, United States, 2Duke Medical Physics Graduate Program, Duke University, Durham, NC, United States, 3GE Healthcare, Aurora, OH, United States |
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Keywords: Shims, RF Arrays & Systems, flexible coil array, localized B0 shimming, integrated RF/shim coil array, iPRES Susceptibility-induced B0 inhomogeneities can cause artifacts that severely degrade the image quality in many applications. Integrated parallel reception, excitation, and shimming (iPRES) coil arrays can perform MRI and localized B0 shimming with a single coil array, but are so far rigid, which limits their SNR and shimming performance. Here, we develop a flexible iPRES coil array that can conform to the subject’s anatomy and substantially improve the SNR and reduce the B0 inhomogeneities and geometric distortions in diffusion-weighted imaging of the knee compared to a rigid iPRES coil array, which will be valuable for many anatomical regions and applications. |
| 4418 | Computer 162
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Design of human brain shim coil with high-density wire pattern translated from Stream Function |
| Shengyue Su1 and Anke Henning1 | ||
1Advance Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States |
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Keywords: Shims, New Devices, Simulations In this work, we propose a B0 shim coil design method based on high-density wire pattern discretized from stream function optimization. We demonstrate that the magnetic field generated by the designed shim coil can fully match the theoretical magnetic field generated by continuous stream functions. We compared the performance of different current-carry surfaces over shim ability for stream function optimization. We also evaluated the impact of current limitation for the discretized coil on B0 shim result and power dissipation. |
| 4419 | Computer 163
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Correction of field drifting for single shot spiral diffusion imaging |
| Tzu Cheng Chao1, Daniel D. Borup2, and James G. Pipe1 | ||
1Department of Radiology, Mayo Clinic, Rochester, MN, United States, 2MR R&D, Royal Philips, Rochester, MN, United States |
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Keywords: System Imperfections: Measurement & Correction, Diffusion Tensor Imaging Diffusion MRI provides useful microstructural information of the soft tissue. Scans using a single-shot Spiral trajectory have demonstrated better geometric fidelity and SNR than those with a Cartesian EPI counterpart. This study shows that the field drifting during a diffusion scan can be a confounding factor to the image quality. A correction strategy exploiting the average off-resonance measurement before and after a scan was applied to mitigate the blurring artifact caused by field drifting. |
| 4420 | Computer 164
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Silent slice-wise shimming with a multi-coil setup at ultrahigh-field MRI |
| Ali Aghaeifar1 and Klaus Scheffler 1,2 | ||
1Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2Biomedical Magnetic Resonance, University Hospital Tübingen, Tübingen, Germany |
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Keywords: Shims, Shims, multi-coil Multi-Coil shimming is advantageous because of its ease of use for effective local and slice-wise shimming. Shim coils are constructed of current-carrying conductor wires and undergo Lorenz force while placed in the magnet. Currents alteration in slice-wise shimming changes the magnitude and direction of force and imposes mechanical vibrations and acoustic noise. Here we propose strategies to control the level of inter-slice shims current change. The proposed strategies showed that inter-slice shims current change can be appropriately reduced by applying a minor change into shimming routine and without degrading shimming performance significantly . |
| 4421 | Computer 165
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On the spatiotemporal phase modulation of odd and even EPI echoes at 300 mT/m diffusion MRI: A field monitoring analysis |
| Gabriel Ramos Llorden1, Daniel Park1, Hong-Hsi Lee1, Alina Scholz2, Boris Keil2, Lawrence L. Wald1,3, Thomas L. Witzel4, and Susie Y. Huang1,3 | ||
1Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States, 2Institute of Medical Physics and Radiation Protection, Mittelhessen University of Applied Sciences, Giessen, Germany, 3Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, 4Q Bio Inc, San Carlos, CA, United States |
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Keywords: Gradients, Brain Most of EPI ghosting algorithms assume that odd/even of phase modulations, either of first or higher spatial order, are stationary through the readout. Hence, a phase maps (or a linear function) for the subset of odd and even k-space lines is judged enough to model Nyquist ghosting and obtaining ghosting free images. Nevertheless, we demonstrate with field monitoring that for high-gradient strength diffusion MRI, persistent eddy currents from the diffusion module interfere non-linearly with the image encoding, leading to phase modulations that are time-varying during the readout. Implications for existing ghosting correction algorithms and potential alternatives are discussed. |
| 4422 | Computer 166
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Self-Grounded Bow-Tie Antennas Placed Perpendicular to B0 in a Helmet RF Array Improve B1+ Uniformity for Brain MRI at 7.0T |
| Faezeh Rahimi1,2, Thomas Wilhelm Eigentler1,3, Bilguun Nurzed1, Jason M. Millward1,4, and Thoralf Niendorf1,4,5 | ||
1Berlin Ultrahigh Field Facility, Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, 2Theoretische Elektrotechnik Institut Hochfrequenz- und Halbleiter-Systemtechnologien, Technische Universität Berlin, Berlin, Germany, 3Chair of Medical Engineering, Technische Universität Berlin, Berlin, Germany, 4a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine, Berlin, Germany, 5MRI.TOOLS GmbH, Berlin, Germany |
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Keywords: RF Arrays & Systems, Modelling, Brain MRI, UHF MRI, PTx UHF-MR uses RF arrays to shape the magnetic field generated inside the brain. For brain MRI at 7T, a helmet shaped transmit RF array could be beneficial versus conventional annular configurations. Recognizing this opportunity this work examines the feasibility of a multi-channel TX helmet RF applicator using broadband Self-Grounded Bow-Tie (bbSGBT) antenna building blocks. The focus is on enhancing B1+ uniformity and coverage for brain MRI at 7.0T. Our findings obtained for the human head voxel model Duke demonstrate improved mean B1+ coverage and increased B1+ uniformity for the helmet configuration. |
| 4423 | Computer 167
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Feasibility of an optimized B0 passive shim helmet based on iron-oxide nanoparticle inks for human brain imaging |
| Hanne Vanduffel1, Nick Arango2, Willy Gsell1, Uwe Himmelreich3, Wim Vanduffel1, Cesar Parra1, Berkin Bilgic4, Clarissa Cooley4, Dimitios Sakellariou1, Rodrigo de Oliviera SIlva1, Lawrence Wald4, Rob Ameloot1, and Jason Stockmann4 | ||
1KULeuven, Leuven, Belgium, 2MIT, Cambridge, MA, United States, 3KULeuven, 3000, Belgium, 4Martinos Center, Charlestown, MA, United States |
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Keywords: Shims, High-Field MRI We present a new method for passive shimming based on 3D printed ferromagnetic inks that are fully compatible with the scanner RF coils. We show simulated B0 shim performance for designs that are optimized to shim the human brain for both a subject-specific passive shim insert and a robust general insert. |
| 4424 | Computer 168
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Retrospective Correction of Second-order Concomitant Fields in 3D Perfusion Imaging with a High-performance Gradient System |
| Afis Ajala1, Seung-Kyun Lee1, Nastaren Abad1, and Thomas Foo1 | ||
1GE Global Research, Niskayuna, NY, United States |
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Keywords: Gradients, Arterial spin labelling, Concomitant Field Correction Magnetic resonance imaging using 3D stack-of-spirals at 3T on a high-performance gradient system such as the MAGNUS can be subject to strong second-order concomitant magnetic fields (SOCG), which can lead to signal dropout and blurring artifacts that become more significant at locations that are farther from the gradient isocenter. SOCG cannot be corrected by pre-emphasis of gradient waveforms and/or radio frequency modulation alone, and hence requires higher-order hardware or software solution. We demonstrate a software-based correction of SOCG in 3D pseudo-continuous arterial spin labelling with a stack-of-spirals k-space trajectory by nulling the phase contributed by SOCG during reconstruction. |
| 4425 | Computer 169
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Robust RF Shimming With Minibatched Magnitude Least Squares Optimization |
| Jonathan B Martin1 and William A Grissom2 | ||
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 2Vanderbilt University, Nashville, TN, United States |
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Keywords: RF Pulse Design & Fields, High-Field MRI We present a magnitude-least-squares RF shimming algorithm which uses interleaved noisy and locally converging updates to escape local minima and find low-cost shim solutions. We introduce noise in the algorithm by performing updates using a small minibatch of the available B1+ measurements. The method is validated using in-vivo head B1+ maps from a 7T scanner. An optimal minibatch size is found which consistently produces low-power and low-RMSE solutions across subjects and through head slices. This shim design method may be employed to more robustly correct for B1+ inhomogeneities at ultra-high field strengths than is possible with conventional methods. |
| 4426 | Computer 170
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Experimental and theoretical investigation of eddy current heating of RF shield in a high-performance gradient system |
| Daehun Kang1, Seung-Kyun Lee2, Erin Gray1, Eric Fiveland2, Yunhong Shu1, Thomas Foo2, and Matt A Bernstein1 | ||
1Radiology, Mayo Clinic, Rochester, MN, United States, 2GE Global Research, Niskayuna, NY, United States |
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Keywords: Gradients, Gradients, Eddy current heating With a high-performance gradient system, gradient-induced eddy current in the RF shield can cause a substantial temperature rise in the patient bore. Especially, a multi-echo EPI sequence involving intense gradient switching and long echo trains, usually lasts for >10 minutes in many resting-state functional MRI studies. The temperature change caused by RF shield heating can jeopardize patient safety and hardware reliability. Based on theoretical and experimental investigation, we demonstrated two main factors that could contribute to the RF shield heating in a high-performance compact 3T scanner, namely the shield surface conductivity and mean-square slew rate of the gradient waveform. |
| 4427 | Computer 171
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Comparison of universal phase shims determined from simulated and measured B1+ maps in the prostate and heart at 7T |
| Saskia Wildenberg1, Nico Egger2, Sophia Nagelstraßer2, Ralph Kimmlingen3, Titus Lanz4, Armin M. Nagel2,5, and Andreas K. Bitz1 | ||
1Electrical Engineering and Information Technology, University of Applied Sciences - FH Aachen, Aachen, Germany, Aachen, Germany, 2Institute of Radiology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany, Erlangen, Germany, 3Siemens Healthcare GmbH, Erlangen, Germany, Erlangen, Germany, 4Rapid Biomedical GmbH, Rimpar, Germany, Rimpar, Germany, 5Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, Heidelberg, Germany |
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Keywords: RF Pulse Design & Fields, Simulations Universal RF shimming is a proven method to avoid the time-consuming process of calculating patient-specific RF shims for every individual subject. Nevertheless, this method requires numerous B1+ maps from in vivo measurements, which is a time-consuming process, especially in the context of product development. This work therefore investigates whether a universal RF shim based on simulated B1+ maps, which are needed for the safety assessment of the coil anyways, is a viable alternative compared to shim optimization based on in vivo data. The study was performed using a torso coil at 7T for the prostate and cardiac region. |
| 4428 | Computer 172
|
Assessment and mitigation of EMI from in-room equipment in the setting of interventional 0.55T MRI |
| Bilal Tasdelen1, Ecrin Yagiz1, Rajiv Ramasawmy2, Ahsan Javed2, Dogangun Uzun2, Dursun Korel Yildirim2, Adrienne Campbell-Washburn2, and Krishna S Nayak1 | ||
1Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, 2Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, United States |
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Keywords: System Imperfections: Measurement & Correction, System Imperfections: Measurement & Correction, EMI, interference, pilot tone Five devices that are relevant in interventional setting and a Pilot-Tone generator are assessed in terms of their electromagnetic interference with 0.55T MRI. Two of the devices (ergometer and flat-panel television) generated significant interference, however acceptable image quality was achieved when using the EDITER interference cancellation technique. EDITER also enabled the use of higher Pilot-Tone amplitudes and use of cheap, general-purpose signal generator for Pilot-Tone generation. |
| 4429 | Computer 173
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Design Optimization of an Hybrid Multi-Coil Array for In Vivo Human Brain B0 Shimming |
| Sebastian Theilenberg1, Carlotta Ianniello1, Kay C Igwe1, Adam M Brickman2,3,4, and Christoph Juchem1,5 | ||
1Biomedical Engineering, Columbia University in the City of New York, New York, NY, United States, 2Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, United States, 3Gertrude H. Sergievsky Center, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, United States, 4Department of Neurology, Columbia University Medical Center, New York, NY, United States, 5Radiology, Columbia University Medical Center, New York, NY, United States |
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Keywords: Shims, Brain The multi-coil (MC) technique utilizing a set of individually driven non-specific coils outperforms traditional spherical harmonics B0 shimming in rodent and human brains. MC designs consisting of dedicated MC elements have shown the best shim performance, while designs utilizing a DC current on the RD coil of RF coil arrays have slightly lower performance but need significantly less physical space. Here, we optimized the number, size and placement of dedicated MC elements to be used in combination with RF-DC coils in a hybrid MC shim system for B0 shimming of the human brain in a clinical 3 T MR scanner. |
| 4430 | Computer 174
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A 16-channel MC and RF hybrid system for B0 shimming and B1 reception: a preliminary prototype |
| Carlotta Ianniello1, Sebastian Theilenberg1, Jonah Majumder1, John Thomas Vaughan1,2,3, and Christoph Juchem1,2 | ||
1Department of Biomedical Engineering, Columbia University in the City of New York, New York, NY, United States, 2Department of Radiology, Columbia University Medical Center, New York, NY, United States, 3Columbia Magnetic Resonance Research Center, Columbia University in the City of New York, New York, NY, United States |
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Keywords: Hybrid & Novel Systems Technology, RF Arrays & Systems, RF Rx array, AC/DC coil, Hybrid RF and shimming We explore the potential of a hybrid approach in which RF receive elements are driven with direct current for B0 shimming (RF+MC) aided with multicoil shim-only elements (MC-only) to overcome the challenging B0 inhomogeneities in the frontal brain. A proof-of-concept implementation consisting of 16 RF+MC elements and 18 MC-only elements is presented. Simulations have shown minimal SNR loss despite the proximity of MC-only elements. Furthermore, the B0 shimming performance of this preliminary setup outperformed 3rd and 5th order SH shimming despite its rudimentary design. Future work will focus on optimizing the B0 performance while minimizing the MC-to-RF coupling. |
| 4431 | Computer 175
|
Eddy-current characterization and pre-emphasis on a compact inside-out nonlinear gradient |
| Ates Fettahoglu1,2, Zhehong Zhang1, Nahla Elsaid1, Andrew Dewdney3, and Gigi Galiana1 | ||
1Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States, 2Radiology, Stanford University, Stanford, CA, United States, 3Siemens Healthcare, Erlangen, Germany |
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Keywords: Hybrid & Novel Systems Technology, Prostate, Eddy-current, GIRF Diffusion-weighted imaging requires strong sensitizing gradients, resulting in eddy currents that create image distortions and hinder the reliability of measured diffusion parameters. In this study, we characterize and and compensate for eddy currents on a compact inside-out nonlinear gradient using a 2D phase encoded FLASH sequence. Time series of the effective waveform was calculated from PCA of the field maps, which was then used to calculate a gradient impulse response function (GIRF). The GIRF was validated by comparing the output waveform of a simple vs pre-emphasized trapezoid. Results showed clear improvement of the pre-emphasized waveform. |
| 4432 | Computer 176
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GIRF-based characterization of a novel cryogen-free HTS magnet |
| Volkert Roeloffs1, Peter Hömmen1, Andreas Voß1, Yi Li1, Robert Odenbach1, Leander Bartsch1,2, Steffen Lother1, and Stefan Röll1,3 | ||
1Neoscan Solutions GmbH, Magdeburg, Germany, 2Otto-von-Guericke University, Magdeburg, Germany, 3Research Campus STIMULATE, Otto-von-Guericke University, Magdeburg, Germany |
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Keywords: System Imperfections: Measurement & Correction, Gradients, eddy currents We characterized our new 1.5 T HTS magnet via GIRF determination. Analysis of time scales showed that relevant first-order eddy currents exhibit time constant of less then 200 µs. This finding is a promising characterization of our system but requires further investigations. |
| 4433 | Computer 177
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Simple Method for Bloch-Siegert B1 Map Data Processing |
| Andrew J Wheaton1 and Wayne R Dannels1 | ||
1Canon Medical Research USA, Mayfield, OH, United States |
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Keywords: System Imperfections: Measurement & Correction, System Imperfections: Measurement & Correction, B1 mapping A simple data processing method for calculating B1 map data using the Bloch-Siegert shift method is described. The proposed method uses a phase conjugate approach instead of conventional phase subtraction. The proposed method has the dual advantages of 1) not requiring phase unwrapping and 2) enabling simple and SNR-efficient complex data combination for multi-channel phased array coils. One consequence of using a phase conjugate approach is a reduced range of resolvable B1 due to phase aliasing. A practical solution is offered to resolve this problem by making an assumption of the realistic range of expected B1. |
| 4434 | Computer 178
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Reliable Low-Field B0-Maps by Deep Learning with Physical Constraints |
| David Schote1, Lukas Winter1, Christoph Kolbitsch1, and Andreas Kofler1 | ||
1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany |
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Keywords: System Imperfections: Measurement & Correction, Low-Field MRI, B0-field map Heavy B0-field inhomogeneities in low-field MRI can lead to geometric distortions in the reconstruction, if not compensated. We simulated low-field data to evaluate different approaches for estimating the field map from phase difference maps. By using spherical harmonic basis functions as physical constraints in our neural network approach we could improve the estimation of B0-field maps compared to other network architectures and methods not involving neural networks. |
| 4542 | Computer 121
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A multiscale approach based on the combination of DTI, XRD and histology to study the myeloarchitecture in a rat model of mTBI |
| Michela Fratini1,2, Isabel San Martín Molina3, Manfred Burghammer4, Tilman Grünewald4,5, Raimo A. Salo3, Omar Narvaez3, Maria Guidi6, Federico Giove6, Manisha Aggarwal7, Jussi Tohka3, Alejandra Sierra3, and Gaetano Campi8 | ||
1Nanotec, CNR, Roma, Italy, 2IRCSS Santa Lucia Foundation, Roma, Italy, 3University of Eastern Finland,, Kuopio, Finland, 4European Synchrotron Radiation Facility, Grenoble, France, 5Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France, 6Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Rome, Italy, 7Russell H. Morgan Department of Radiology and Radiological Science, , John Hopkins University School of Medicine, Baltimore, MD, United States, 8Institute of Crystallography, CNR, Rome, Italy |
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Keywords: Multimodal, Tissue Characterization, x ray scanning diffraction We have combined high-resolution structural imaging techniques, such as scanning micro-X-ray diffraction (SμXRD), DTI and histology to study the myeloarchitecture in both healthy and pathological rat brains. For the latter, we focused on an animal model of mild traumatic brain injury (mTBI) that is the most common form of acquired brain injury caused by an external force into the brain. We have performed a quantitative morphometrical analysis of myelin, mapping its relevant morphological and topological parameters (period, orientation, and integrated intensity fluctuation) to assess tissue microstructural damage 35 days after mTBI and sham-operation |
| 4543 | Computer 122
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Continuous wave radar for carotid pulse sensing in Magnetic Resonance Imaging |
| Renesmee Kuo1, John Pauly1, Fraser Robb2, Shreyas Vasanawala1, and Greig Scott1 | ||
1Stanford University, Stanford, CA, United States, 2GE HealthCare, Aurora, OH, United States |
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Keywords: Hybrid & Novel Systems Technology, Image Reconstruction Non-contact synchronization MRI with heart motion is still an open challenge. Inaccurate cardiac gating often complicates image reconstruction and leads to poor or non-diagnostic images. Continuous wave doppler radar is a non-contact, noninvasive novel systems technology that could monitor cardiac motions without distortion from the MRI electromagnetic environment while offering an alternative to state-of-the-art (ECG) triggering. |
| 4544 | Computer 123
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Design and Implement Active Twin-T Notch Filter for Signal Reception in Magnetic Particle Imaging |
| Kangjian Huang1, Congcong Liu1, Ye Li1, Yanjie Zhu1, Hairong Zheng1, Dong Liang 1, and Haifeng Wang1 | ||
1Shenzhen Institute of Advanced Technology，Chinese Academy of Sciences, shenzhen, China |
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Keywords: Hybrid & Novel Systems Technology, Hybrid & Novel Systems Technology Because of the imaging coding mode of Magnetic particle imaging (MPI), the drive-field signal directly couples into the receiving coil and covers the magnetic particle signal, which one aims to detect. Therefore, some method is needed to remove the drive-field signal and retain the magnetic particle signal. One of the methods is to use a passive band-stop filter to filter the excitation signal, but the general passive band-reject filter has a large stopband, which filters part of the magnetic particle signal while filtering the drive-field signal. In this study, we design an active twin-T notch filter with narrow stopband, which better restore the magnetic particle signal and improve the signal-to-noise in MPI. |
| 4545 | Computer 124
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AI inspired engineering of future MRI machines and components |
| J. Coupling1, E. Current1, and Line SP. Litting1 | ||
1Division of Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany |
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Keywords: Hybrid & Novel Systems Technology, New Devices The topic of this contribution is how artificial intelligence (AI) can be used to engineer future magnetic resonance imaging (MRI) machines and components. MRI machines are vital tools in the medical field, used for everything from diagnosing injuries to detecting cancer. However, they are also extremely complex devices, made up of many different parts that must work together seamlessly. |
| 4546 | Computer 125
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Feasibility of high-frequency shear wave MR elastography of the parotid glands |
| Vitaliy Atamaniuk1, Jun Chen 2, Kevin Glaser2, Andrii Pozaruk1, Marzanna Obrzut3, Bogdan Obrzut4, Wojciech Domka5, Krzysztof Gutkowski6, Richard L Ehman2, and Marian Cholewa1 | ||
1Department of Biophysics, Institute of Physics, College of Natural Sciences, University of Rzeszow, Rzeszow, Poland, 2Department of Radiology, Mayo Clinic, Rochester, MN, United States, 3Center for Diagnostic Medical Sonography, Rzeszow, Poland, 4Department of Obstetrics and Gynecology, Institute of Medical Sciences, Medical College, University of Rzeszow, Rzeszow, Poland, 5Department of Otorhinolaryngology, Institute of Medical Sciences, Medical College, University of Rzeszow, Rzeszow, Poland, 6Institute of Medical Sciences, Medical College, University of Rzeszow, Rzeszow, Poland |
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Keywords: New Devices, Elastography A specialized driver was developed to enable magnetic resonance elastography of the parotid and other salivary glands using high shear wave frequencies to provide improved spatial resolution and optimized ergonomics. The performance of this new device was tested in volunteer studies. Preliminary results showed that suitable shear wave illumination of the parotid gland is possible at frequencies as high as 120 Hz and that high-frequency shear wave MR elastography of the parotid gland is feasible. |
| 4547 | Computer 126
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Monitoring performance of a GaN HEMT switch across different magnetic field strengths for implementation of On-Coil Tx Amplifiers |
| Brett Setera1,2, Aristos Christou2, and Natalia Gudino1 | ||
1Laboratory of Functional and Molecular Imaging, National Institutes of Health, Bethesda, MD, United States, 2Department of Materials Science & Engineering, University of Maryland, College Park, MD, United States |
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Keywords: New Devices, New Devices, Radiofrequency Technology We present a method for monitoring multiple GaN HEMT device signals at different orientations with B0 during RF switching to determine possible magnetic field impacts on device performance and assist the development of an optimized GaN based device for on-coil amplification. Reduction in output current with increased magnetic field strength were not detected and device orientation did not impact signal amplitude. |
| 4548 | Computer 127
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Postmortem Imaging with Reusable 3D Printed Ex Vivo Brain Enclosures/Cutting Guide for MRI Registration with Gross Anatomy Photographs at 7T |
| Jacob Patrick Berardinelli1, Julia Kofler2, Jinghang Li3, Owen Flaugh3, Nadim Farhat3, Tales Santini3, Andrea Sajewski3, Noah Schweitzer3, Joseph Mettenburg2,3, Milos Ikonomovic2, Howard J. Aizenstein3, and Tamer S. Ibrahim3 | ||
1Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States, 2UPMC, Pittsburgh, PA, United States, 3University of Pittsburgh, Pittsburgh, PA, United States |
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Keywords: New Devices, Ex-Vivo Applications The ability to continuously prototype and 3D print new containers as well as using an improved transmit coil has led to major improvements in ex-vivo image quality. This has also allowed for a more automated registration process of the MR images to the gross anatomy
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| 4549 | Computer 128
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MRI IN RADIATION THERAPY: VALIDATION OF THE EFFECT FROM BLANKET MRI-COIL ON THE PELVIS REGION OF HEALTHY VOLUNTEERS |
| Yosef Al-Abasse1, Tova Roman Rung1, Peter Larsson1, Dan Josefsson1, Lena Lundkvist2, Kristina Redelius2, Kristina Hultman2, Maria Nilsson2, Jan Rzepecki2, and Peter Lundberg1,3 | ||
1Department of Health, Medicine and Care, Linköping University, Linköping, Sweden, 2Department of Oncology, and Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden, 3Center for Medical Imaging and Visualization (CMIV), Linköping University, Linköping, Sweden |
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Keywords: Multimodal, Radiotherapy, Synthetic CT, T2-w, software Conventional coils for dose planning purposes cannot be placed on the patient as the outer body contour then will be deformed. Coils are therefore placed on a special holder which creates a distance between coil and patient, but this leads to less SNR. The blanket-coils are significantly lighter and can be placed directly on the patient. Three similarity comparison methods were used here, Hausdorff distance, Dice similarity coefficient (DSC) and Surface DSC. Eight of eleven comparisons were within 4 mm difference for Hausdorff distance; Surface DSC was >99%, at a 3 mm tolerance, and DSC >98.5%.
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| 4550 | Computer 129
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Benchtop NMR for lab-on-a-chip |
| Marc Azagra1, Alejandro Portela1, Hetal Patel2, Dian Weerakonda2, Jose Yeste1, Alba Herrero-Gómez1, Matthew Fallon2, Megdouda Benamara3, Marc Dubois3, Tryfon Antonakakis3, Javier Ramon1, and Irene Marco-Rius1 | ||
1Institute for Bioengineering of Catalonia, Barcelona, Spain, 2Oxford Instruments, Abingdon, United Kingdom, 3Multiwave Imaging, Marseille, France |
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Keywords: New Devices, Hyperpolarized MR (Non-Gas), Molecular Imaging A benchtop NMR spectrometer has been designed and optimized to monitor real-time metabolism of 3D tissue engineered on microfluidic platforms using hyperpolarization by dynamic nuclear polarisation. We show the design process, which included the modification of a commercial benchtop NMR spectrometer, the design and fabrication of a microfluidic platform for a reliable injection of a hyperpolarized substrate and a constant delivery and renewal of the cell media and its integration with a RF coil for transmit/receive, and the design and fabrication of a sample carrier. We also present our preliminary NMR data using this system. |
| 4551 | WITHDRAWN |
| 4552 | Computer 130
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Development of a MR-compatible bioreactor for 3D cell structure metabolic analysis in real-time for a 60 MHz benchtop NMR spectrometer. |
| Lluís Mangas-Florencio1, Alba Herrero-Gómez1, Marc Azagra1, James Ellis1, and Irene Marco-Rius1 | ||
1Institute for Bioengineering of Catalonia, Barcelona, Spain |
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Keywords: New Devices, Cancer, Metabolism Bioreactor platforms have been used in HP-NMR applications to analyze cellular metabolism in real-time, however they require complex set-ups and automated controlled systems, limiting their use. We present a system that overcomes these limitations consisting of a 3D printed platform, an NMR compatible 3D cell model and a recirculation circuit for single-shot and longitudinal hyperpolarization-enhanced NMR experiments. The platform presents no signal interference, a media system for biological support, and a straightforward and simplified manufacturing and assembly process. As a proof-of-concept, we present preliminary metabolic data of a 3D HeLa cell model analyzed with our bioreactor. |
| 4553 | Computer 131
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An in-bore PIN diode driver based on a single chip with nanoseconds rise/fall time |
| Christoph Michael Schildknecht1, Russell L Lagore2, Matt Waks2, Gregor Adriany2, and Klaas Paul Pruessmann1 | ||
1Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zürich, Switzerland, 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States |
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Keywords: New Devices, New Devices An in-bore PIN diode driver with eight output channels is presented here. The driver is based on a single-chip solution making the implementation simple and of high performance. The rise and fall times of the driver's output are in the single-digit nanosecond range with a peak output current of up to 5.7A per channel. Triggering the driver can be done either with an optical or electrical signal. The driver was tested on the bench and in-bore of a 10.5T MR scanner. |
| 4554 | Computer 132
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Ultra-thin metasurface pads for spine MRI |
| Marc Dubois1, Amira Trabelsi1,2,3, Tania Vergara Gomez1,2,3, Pierre Jomin3, Djamel Berrahou1, David Bendahan2,4, Frank Kober2,4, Virginie Callot2,4, Stefan Enoch3, and Redha Abdeddaim3 | ||
1Multiwave Imaging, Marseille, France, 2Aix Marseille Univ, CNRS, CRMBM, Marseille, France, 3Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France, 4APHM, Hopital Universitaire Timone, CEMEREM, Marseille, France |
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Keywords: New Devices, Spinal Cord, Metamaterial, Metasurface Spine imaging is usually conducted at 3T given the need of high spatial resolution. Unfortunately, the lumbar and thoracic spine regions of interest will lie in areas of weak transmit efficiency. Recent studies showed that high permittivity ceramic blocks can improve image quality. Here we present a new approach based on ultra-thin, lightweight, flexible metasurface pads yielding improved efficiency and homogeneity of the B1+ field along the spine in clinical 3T MRI settings. Our design offers seamless integration to regular equipment leading to more efficient and safer spine imaging protocols. |
| 4555 | Computer 133
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The MR-Bioreactor : Micro-MRI of thick living tissues to characterize 4-days old ex-ovo chick embryo morphology. |
| Jean-Lynce Gnanago1, Sophie Calvet2, Tony Gerges1, Valernst Gilmus1, Camila Pereira Sousa1, Michel Cabrera1, Julien Falk2, and Simon Auguste Lambert1 | ||
1Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale de Lyon, CNRS, Ampère UMR5005, Villeurbanne, France, Lyon, France, 2MeLis, CNRS UMR 5284-INSERM U1314-Université Claude Bernard Lyon 1 Institut NeuroMyoGène, Lyon, France, Lyon, France |
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Keywords: New Devices, Animals Thanks to their accessibility for experimental manipulations, their availability and their low cost, chick embryos have been used as animal models for developmental biology for long. In these applications, non-invasive 3D imaging of the embryos is needed to monitor the embryos development. Morphological characterization of ex-ovo chick embryo generally require tissue fixing which can alter MR characterizations. In this work, we use our MR-Bioreactor to perform a high resolution morphological characterization of a chick embryo maintained in living conditions. |
| 4556 | Computer 134
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Silicon Carbide (SiC) Based Flexible and Stretchable Dielectric Pad for B1 Field Enhancement |
| Seyedamin Hashemi1, Kezia Sharon Christopher1, Sri Kirthi Kandala1, Kwanjoon Song2, Benjamin Bartelle1, and Sung-Min Sohn1 | ||
1School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States, 2Department of Biomedical engineering, Yonsei University, Wonju, Korea, Republic of |
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Keywords: New Devices, RF Arrays & Systems, Invisible Dielectric pad, Silicon Carbide, SNR enhancement We propose a stretchable, flexible, and MRI invisible dielectric pad to enhance the quality of acquired MR images. A silicon-based elastomer is mixed with Silicon Carbide (SiC) to develop this proposed dielectric pad. Preclinical in-vivo imaging of a mouse head was conducted at 9.4T to validate the performance of the dielectric pad. 2.54% (in dB) increase in the central SNR of the brain was observed after using the dielectric pad and peripheral brain locations have shown improved contrast. The flexible and stretchable dielectric pad could be used as a substitute for conventional dielectric pads, especially in irregular sample shapes. |
| 4557 | Computer 135
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A Design of 10-100 MHz Broadband NMR Transmission-line Probe |
| Shouquan Yao1, Juncheng Xu1, Yiqiao Song2, Ming Shen1, Bingwen Hu1, and Yu Jiang1 | ||
1Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai, China, 2Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States |
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Keywords: New Devices, New Devices, Probe This work demonstrated a broadband NMR probe with a bandwidth of 10-100 MHz. Based on transmission-line structure, broadband transmission was achieved. As for broadband reception, high-speed active T/R switches and low-noise differential amplifiers were used for high-sensitivity RF reception. The SNR of FID signal detected by broadband probe was 74% of that of conventional resonance probe, which means the feasibility of the broadband NMR transmission-line probe was verified. |
| 4558 | Computer 136
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State of Art, Powerful, System On Chip, Design,Development and Implementation of Multi Channel Transceiver for MRI Spectrometer |
| Rajesh Harsh1, Dharmesh Verma1, Aparna Gunvant Raut1, and Mahadev Kashinath Dipnaik1 | ||
1Medical Systems Division, S.A.M.E.E.R. Mumbai, Mumbai, India |
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Keywords: New Devices, Spectroscopy, System -on-chip,MIMO Based smart MRI Spectrometer The increasing complexity of modern MRI hardware design makes system challenging. MRI systems equipped with multi-channel exciter and multi-channel data-acquisition modules, particularly high-channel-counts often requires a huge cost. This abstract summaries the design and development of a low cost, small form factor, system on chip approach to realize a complete 1.5 T MRI spectrometer on a small chip of 28 nanometer fabric. The developed system executes parallel image processing algorithms and compatible instrumentation for accurate spatial and temporal requirements. |
| 4559 | Computer 137
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Developing an In-Bore MRI-Compatible Syringe Pump |
| Martin D Holland1, Seth N Lee2, and Harrison D Kim2 | ||
1Interdisciplinary Engineering, University of Alabama at Birmingham, Birmingham, AL, United States, 2Radiology, University of Alabama at Birmingham, Birmingham, AL, United States |
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Keywords: New Devices, New Devices, Syringe pump, MRI Compatibility, 3D Printing Delivering a contrast (or therapeutic) agent to a subject inside an MRI bore requires an expensive electronically programmed syringe pump and a long tube filled with the agent. We developed an inexpensive 3D-printed MRI-compatible syringe pump that can be used inside an MRI bore. This syringe pump yields a highly reproducible infusion rate, which can be readily adjusted using gears with different gear ratios. |
| 4560 | Computer 138
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Falling conductive loop: A simple analytical model for magnetic damping |
| Seung-Kyun Lee1 | ||
1GE Global Research, Niskayuna, NY, United States |
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Keywords: Magnets (B0), Magnets (B0), magnetic damping The motion of a conductive object is profoundly affected by the presence of a strong magnetic field. A conductive loop falling inside an MRI magnet can serve as an analytically solvable model to explore magnetic damping. We present a pair of magneto-mechanical coupled equations to describe its motion and verify their solution with experimental data. A simple formula for the loop's falling time was obtained, which indicates that magnetic damping is proportional to B02. |
| 4561 | Computer 139
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Open-Bore Hybrid MPI-MRI Scanner: A Proof-of-Concept Simulation Study |
| Sefa Karaca1,2,3, Damla Alptekin Soydan1, Emine Ulku Saritas2,3, and Can Barış Top1 | ||
1Aselsan Research Center, ASELSAN A.Ş., Ankara, Turkey, 2Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, 3National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey |
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Keywords: Hybrid & Novel Systems Technology, Low-Field MRI, Magnetic Particle Imaging Magnetic particle imaging (MPI) is a novel technique that images background-free spatial distribution of magnetic nanoparticles inside the body. The lack of signal from the background tissue provides high sensitivity to MPI. However, anatomical information is also required in many applications. Here, we present an open-bore hybrid preclinical MPI-MRI system, in which the coils can be utilized interchangeably between MPI and MRI data acquisitions. We analyze the imaging performance for both modalities using a simulation model based on our in-house prototype MPI system that can generate 0.5 T/m selection field gradients for MPI and 50 mT B0 for low-field MRI. |
| 4562 | Computer 141
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RF pulse optimization for robust excitation in 31P magnetization transfer spectroscopy |
| Christina Graf1, Clemens Diwoky2, Armin Rund3, and Rudolf Stollberger1 | ||
1Institute of Biomedical Imaging, Graz University of Technology, Graz, Austria, 2Institute of Molecular Biosciences, Karl-Franzens University Graz, Graz, Austria, 3Institute for Mathematics and Scientific Computing, Karl-Franzens University Graz, Graz, Austria |
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Keywords: RF Pulse Design & Fields, RF Pulse Design & Fields In this work, robust excitation pulses for 31P spectroscopy at 7T are designed by optimal control. The particular challenges of inhomogeneous RF field due to use of surface RF coils and broad bandwidth requirements due to the nature of 31P were addressed thoroughly. The optimized RF pulses show superior performance compared to adiabatic RF pulses during numerical simulations and phantom experiments. Application of the optimized RF pulses to T1 prediction by dual angle method is the logical consequence. |
| 4563 | Computer 142
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RF Pulse Predistortion for Low-Field MRI Based on Spin Physics Using a Neural Network Amplifier-to-Bloch Equation Model |
| Madison M Albert1, Christopher E Vaughn1, Jonathan B Martin1, Sai Abitha Srinivas1, and William A Grissom1 | ||
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States |
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Keywords: RF Pulse Design & Fields, Low-Field MRI, Amplifiers, Predisortion In low-field MR, low-cost amplifiers with reduced fidelity are used. Current solutions to this problem require additional hardware and do not optimize the pulse for the final excitation profile. The proposed methodology models the amplifier with a neural network, connects the network to a Bloch simulator, and optimizes the pulses for the desired excitation profile. In simulation, a windowed sinc pulse (time-bandwidth product = 10, phase = 0 radians, duration = 1 ms) was optimized to minimize the loss between the target profile and the generated profile after the pulse passes through the amplifier to 0.05% of the starting loss. |
| 4564 | Computer 143
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Simultaneous Saturation and Excitation (SatEx) pulse |
| Shota Hodono1, Chia-yin Wu1,2,3, Carl Dixon1, Donald Maillet1, Jin Jin4, Jonathan R Polimeni5,6, and Martijn A Cloos1 | ||
1Centre for Advanced Imaging, The University of Queensland, St. Lucia, Australia, 2ARC Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, St. Lucia, Australia, 3chool of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia, Australia, 4Siemens Healthcare Pty Ltd, Brisbane, Australia, 5Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, 6Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States |
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Keywords: RF Pulse Design & Fields, Velocity & Flow We propose a new slice-selective excitation pulse that simultaneously saturates magnetization adjacent to it. The Saturation and Excitation (SatEx) pulse is a summation of two asymmetric sinc pulses whose leading lobes have been cut combined with an asymmetric excitation pulse with its final lobes truncated. The saturation and excitation slice profile were validated in simulations and a flow-phantom scan. The flow-phantom scan showed strong saturation of inflow effects. Since the SatEx pulse is as short as a conventional sinc excitation pulse, it can be implemented in a wide range of fast imaging sequences to suppress inflow effects without lengthening TR. |
| 4565 | Computer 144
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Design and Optimization of a MultiPINS Prepulse for Two-dimensional Ultrashort Echo Time Simultaneous Multi-slice Pulse Sequences |
| Jason A Reich1, Erin MacMillan2,3,4, and Rebecca Feldman1,5 | ||
1Computer Science, Mathematics, Physics and Statistics, University of British Columbia, Kelowna, BC, Canada, 2UBC MRI Research Centre, Department of Radiology, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada, 3SFU ImageTech Lab, Simon Fraser University, Surrey, BC, Canada, 4Philips Canada, Mississauga, ON, Canada, 5Biomedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States |
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Keywords: RF Pulse Design & Fields, RF Pulse Design & Fields It has been challenging to achieve ultrashort echo times with two-dimensional acquisitions. However, the use of a prepulse and a whole volume hard excitation may address these limitations. In addition, such a pulse sequence would allow for the use of simultaneous multi-slice pulses to reduce scan times. We aim to design a low specific absorption rate, short duration MultiPINS prepulse that excites a slice profile with sharp, narrow slice gaps. Optimization suggests that a pulse with time bandwidth product (TBW) of 49.43 is optimal, but further investigation suggests that a pulse with TBW as low as 36 may be feasible. |
| 4566 | Computer 145
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Analytical expression for gradient eddy current-induced power dissipation in a thin conductive shell: A model for RF shield heating |
| Seung-Kyun Lee1, Matthew Tarasek1, Yihe Hua1, Keith Park1, Daehun Kang2, Matt A Bernstein2, and Thomas Foo1 | ||
1GE Global Research, Niskayuna, NY, United States, 2Mayo Clinic, Rochester, MN, United States |
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Keywords: Gradients, Gradients, eddy current Gradient-induced eddy current in an RF shield can cause significant temperature increase in the patient bore. As gradient coils produce higher amplitudes with faster rise time, understanding and controlling eddy-current heating become more and more important for patient safety and device longevity. Through time-domain analysis, we have derived a mathematical formula that relates the eddy-current heating of a uniform conductive shell to the properties of the conductor and the mean-square slew rate of the gradient waveform. The theoretical prediction was tested by experiments performed on a high-performance head-only gradient (MAGNUS) system. |
| 4567 | Computer 146
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Subject Specific Prediction of Gradient-Induced E-fields Using a Multivariate Linear Modeling Approach |
| Koray Ertan1, Peter B Roemer2, and Brian Rutt1 | ||
1Radiology, Stanford University, Stanford, CA, United States, 2Roemer Consulting, Lutz, FL, United States |
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Keywords: Gradients, Gradients, PNS, Peripheral Nerve Stimulation, Safety, Bioeffects, Magnetic Fields Peripheral Nerve Stimulation (PNS) remains as a limiting factor for gradient coils despite the recent advances. PNS thresholds varies significantly across population group. In this study, E-fields are simulated on simplified body model population with randomized realistic body dimensions and different patient landmark positions. It is shown that multivariate linear model with body dimensions and z-offset location as the independent variables can accurately predict the maximum E-field on the surface which can also be used to predict PNS thresholds. This simple multivariate model may pave the way to estimate subject specific PNS thresholds using simple anatomical measurements. |
| 4568 | Computer 147
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Modelling the gradient system as linear and time-invariant: Do the assumptions break down at higher field strength? |
| Stefan Sommer1,2,3, Herbert Köstler4, and Hannah Scholten4 | ||
1Siemens Healthineers International AG, Zurich, Switzerland, 2Swiss Center for Musculoskeletal Imaging (SCMI), Balgrist Campus, Zurich, Switzerland, 3Advanced Clinical Imaging Technology (ACIT), Siemens Healthineers International AG, Lausanne, Switzerland, 4Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Würzburg, Germany |
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Keywords: System Imperfections: Measurement & Correction, Gradients, GIRF, GSTF The gradient system transfer function (GSTF) is a broadly used model to characterize the gradient chain and correct for imperfections e.g. in non-Cartestian sampling trajectories. The model assumes linearity and time-invariance (LTI) of the system. In this work, we indirectly examine the LTI compliance across two different field strengths by comparing different GSTFs based on varying subsets of input gradient shapes for the model computation. Overall, only small changes in the GSTF were observed upon adding different input gradients for the system characterization. However, the differences were more pronounced at 7T compared to 3T. |
| 4569 | Computer 148
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Vector concomitant field mapping by phase contrast imaging |
| Seung-Kyun Lee1 and Afis Ajala1 | ||
1GE Global Research, Niskayuna, NY, United States |
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Keywords: Gradients, Gradients, concomitant field We show that concomitant field-induced phase in phase-contrast imaging allows measurement of the transverse (x,y) components of the magnetic field generated by a gradient coil. Combined with conventional B0 mapping which gives the z-component, the method permits experimental determination of the full three-dimensional vector magnetic field of a gradient coil. We demonstrate the method on a high-performance head gradient (MAGNUS) system and discuss its application to concomitant-field artifact correction based on one-time calibration. |
| 4570 | Computer 149
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Characterizing gradient performance and estimating Maxwell fields at 0.55T. |
| Daniel West1, David Leitão1, Raphael Tomi-Tricot1,2, Tobias C Wood3, Jo Hajnal1,4, and Shaihan Malik1,4 | ||
1Biomedical Engineering, King's College London, London, United Kingdom, 2MR Research Collaborations, Siemens, Frimley, United Kingdom, 3Department of Neuroimaging, King's College London, London, United Kingdom, 4Centre for the Developing Brain, King's College London, London, United Kingdom |
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Keywords: System Imperfections: Measurement & Correction, Gradients In this work we use a general sequence to characterize gradient imperfections at low field (0.55T) by measuring the gradient impulse response function (GIRF). Maxwell fields become non-negligible at lower field strengths and so we incorporate these into our GIRF calculation to form a single processing pipeline. Once the predictive ability of the GIRF was confirmed, we use our data to estimate the Maxwell phase and compare this to an analytic approach; good agreement is observed. These results will inform future low-field investigations and enable an improved image quality for sequences that are particularly prone to gradient imperfections. |
| 4571 | Computer 150
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MRI Simulations for Complex 3D Flow using the Lattice Boltzmann Method |
| Ansgar Adler1, Nick Scholand1, Jost Kollmeier2, Yong Wang3,4, and Martin Uecker1,4,5 | ||
1Insitute of Biomedical Imaging, Graz University of Technology, Graz, Austria, 2Biomedical NMR, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany, 3Department of Fluid Physics, Pattern Formation, and Biocomplexity, Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany, 4DZHK (German Centre for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany, 5Institute of Diagnostic and Interventional Radiologie, Göttingen, Germany |
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Keywords: Phantoms, Velocity & Flow, Simulation The lattice Boltzmann method (LBM) is a versatile technique to simulate fluid dynamics in complex environments. We extended the LBM to flows with a spin 1/2 degree of freedom in external magnetic fields. We performed 3D simulations for FLASH MRI of a laminar flow in a pipe and the complex flow of the Karman vortex street. |
| 4572 | Computer 151
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Thermal Model in Feedforward Control of the Gradient Array System in MRI |
| Ege Aydın1,2, Reza Babaloo1,2, and Ergin Atalar1,2 | ||
1Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, 2National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey |
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Keywords: Gradients, System Imperfections: Measurement & Correction Resistive elements in a gradient system, namely the gradient coil and the amplifier, causes heating and the total system resistance to increase. With feedforward controllers, such changes cause inaccurate gradient fields to occur, which in turn causes image artifacts. To mitigate self-heating caused resistance change issues, modeling the gradient system's thermal behavior is necessary. Such a model introduces additional parameters to the overall feedforward model, and identifying these parameters correctly is essential for accurate current waveforms. For this purpose, we propose a method to extract these parameters along with a more complete thermal model. |
| 4573 | Computer 152
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A Novel Method to Estimate and Control the Eddy Power Loss within the Cryostat: A Co-Simulation Approach to Tune Z-Gradient Array Coil |
| Manouchehr Takrimi1 and Ergin Atalar1,2 | ||
1UMRAM, Bilkent University, Ankara, Turkey, 2Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey |
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Keywords: Gradients, Hybrid & Novel Systems Technology, Gradient Array Coils We propose a fast computational method based on a series of electromagnetic simulations to calculate a proper set of feeding currents for a z-gradient array coil that dynamically provides the best shield for its primary array coil. The net magnetic field generated by each array element is calculated, and the total average eddy power (energy) loss resulting from fast-switching stray fields inside the cryostat assembly is estimated and controlled. Two design scenarios with comparable performance criteria are offered for a 48-element z-gradient array coil. The accuracy of the estimated eddy power losses is compared with that of commercial software. |
| 4574 | Computer 153
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The effects of RF channel numbers on |B1+| mapping using the BSS method |
| Yinhao Ren1, Yunyu Gao2, Bensheng Qiu3, Xiang Nan4, and Jijun Han1 | ||
1School of Biomedical Engineering, Anhui Medical University, Hefei, China, 2School of Biomedical Engineering, Southern Medical University, Guangzhou, China, 3Center for Biomedical Imaging, University of Science and Technology of China, Hefei, China, 4Department of Anatomy, Anhui Medical University, Hefei, China |
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Keywords: RF Pulse Design & Fields, Brain In the BSS method, WA and MLE as two methods in channel combination were proposed in |B1+| mapping for the multi-channel coils. We investigated the effects of the channel numbers on the performance of WA and MLE. The results showed the accuracy of |B1+| maps improved with the channel numbers increasing, even at low SNR. However, this trend slowed down when the channel numbers reached 24 or above. The RSD of WA and MLE was reduced to 6.6% and 4.0% for 24-channel coils, but the improvements were only 1.0% and 0.7% for 32-channel coils at SNR=25. |
| 4575 | Computer 154
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Diffusion Weighted Imaging using a Prostate Nonlinear Gradient Coil |
| Nahla M H Elsaid1, Terence Nixon1, Andrew Dewdney2, Andrea De Simone3, Ates Fettahoglu1, and Gigi Galiana1,4 | ||
1Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States, 2Magnetic Resonance, Siemens Healthcare GmbH, Erlangen, Germany, 3Università Cattolica del Sacro Cuore, Rome, Italy, 4Biomedical Engineering, Yale University, New Haven, CT, United States |
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Keywords: Gradients, Prostate This work presents the early performance characteristics of an inside-out prostate nonlinear gradient (NLG). Diffusion-weighted imaging (DWI) could detect prostate cancers non-invasively. However, it requires high b-values, which in turn require a gradient pulse with a long duration, increasing the echo time. A longer echo time means a lower SNR and lower contribution from short T2 components. NLG coil circumvents this issue by having a gradient with a high amplitude within a limited field of view, which applies to prostate imaging. |
| 4576 | Computer 155
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Open-source, low-cost device for visualizing static magnetic field components at 0.25 T and 3 T |
| Folk W. Narongrit1, Thejas Vishnu Ramesh2, T Arthur Terlep1, Antonia Susnjar2, and Joseph V. Rispoli1,2 | ||
1Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, United States, 2Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States |
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Keywords: Magnets (B0), New Devices We present a low-cost (<$17 USD per channel), open-source, and scalable prototype for visualizing the three-axis static magnetic field components up to 3 T based on the GaAs Hall effect technology. The prototype showed accuracy and stability on the bench and accurately measured field values in a 0.25 T electromagnet and a 3 T MRI scanner. |
| 4577 | Computer 156
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A High Performance Gradient and RF Insert for Dental MRI |
| Philipp Amrein1, Serhat Ilbey2, Sebastian Littin2, Feng Jia2, Michael Bock2, Maxim Zaitsev2, and Ali Caglar Özen2 | ||
1Division of Medical Physics, Department of Radiology, University Medical Center Freiburg, Germany, Freiburg, Germany, 2Division of Medical Physics, Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, Freiburg, Germany |
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Keywords: Gradients, New Devices, Dental MRI Dental MRI requires high resolution imaging, e.g., for detection of root canals, as well as, high readout bandwidth for short T2* tissues, such as dentin and nerve fibers. These requirements can only be satisfied by high-performance gradients. In this study, we show with Bloch simulations the necessity for high performance gradients, and consequently introduce a gradient and RF insert, which is optimized for dental MRI. We also explore the concept a cylindrical encoding for curved slices for 4-fold acceleration compared to conventional encoding. |
| 4578 | Computer 157
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Reproducibility of field from an easily installed insert gradient coil for prostate DWI |
| Zhehong Zhang1, Nahla M H Elsaid2, Terry Nixon1,2, Andrew Dewdney3, and Gigi Galiana1,2 | ||
1Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University, New Haven, CT, United States, 2Department of Radiology and Biomedical Imaging, School of Medicine, Yale University, New Haven, CT, United States, 3Siemens Healthcare, Erlangen, Germany |
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Keywords: Gradients, New Devices, Insert gradient coil A compact, lightweight device that generates a strong nonlinear gradient was recently developed for prostate DWI. In principle this hardware can be installed/removed for individual scans, but an additional question is whether the gradient field would need to be mapped and characterized with each installation. This work shows high reproducibility of the field after different installations, implying a single high quality field map can be reused. This result paves the way for practical clinical use of this insert gradient. |
| 4579 | Computer 158
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Central SNR Gain from the Field Strength: Evaluation of Current RF Coil Technology |
| Alireza Sadeghi-Tarakameh1, Andrea Grant1, Matt Waks1, Nader Tavaf1, Russell L Lagore1, Lance DelaBarre1, Edward Auerbach1, Gregor Adriany1, Pierre‐Francois Van de Moortele1, Kamil Ugurbil1, and Yigitcan Eryaman1 | ||
1Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, MN, United States |
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Keywords: RF Arrays & Systems, High-Field MRI Higher signal-to-noise ratio (SNR) is the primary motivation for increasing the magnetic field strength of MRI scanners. However, advanced technology, including state-of-art radiofrequency receiver coils, is strictly required to realize the SNR gain from field strength. In this study, we experimentally investigate the capability of conventional loop technology to capture central SNR gain from field strength for head applications. For this purpose, we evaluated the SNR performance of several loop receiver arrays at 3T, 7T, and 10.5T. We showed that realizing the SNR gain from the UHF will likely require RF coil technologies other than the conventional receiver loop arrays. |
| 4580 | Computer 161
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Prostate Imaging at 7 Tesla: Comparison of Two 8-channel Transmit/Receive RF Local Body Arrays |
| Markus W. May1,2, Oliver Kraff1, Jenni Schulz3, Stephan Orzada4, Sebastian Schmitter5, Thomas Meurs6, Mark van Uden6, Tom Scheenen3, and Harald H. Quick1,2 | ||
1Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany, 2High-Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, 3Department of Medical Imaging, Radboud University Medical Center, Nijmegen, Netherlands, 4Medical Physics in Radiology (E020), German Cancer Research Center (DKFZ), Heidelberg, Germany, 5DZHK (German Center for Cardiovascular Research), DZHK (German Center for Cardiovascular Research), Partner Site Berlin, Berlin, Germany, 6Tesla Dynamic Coils, Zaltbommel, Netherlands |
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Keywords: RF Arrays & Systems, Body The purpose of this study is to compare two different coil array designs for prostate imaging. We compared an in-house developed 8chpTx/Rx micro stripline element coil array with meanders to a recently introduced, commercially available 8chpTx/Rx coil array based on fractionated dipoles for 1H prostate imaging at 7T. Both coil arrays showed comparable results in the phantom and in vivo examinations. The commercially available coil array performs slightly better in the region of the prostate and is well suited for future prostate imaging at 7T. |
| 4581 | Computer 162
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Eight-channel transceiver array for combined head and neck imaging at 7 Tesla |
| Divya Baskaran1, Paul McElhinney1, Sydney Williams1, Sarah Allwood Spiers2, David Porter1, and Shajan Gunamony1 | ||
1Imaging Centre of Excellence, University of Glasgow, Glasgow, Scotland, 2MRI Physics, NHS Greater Glasgow and Clyde, Glasgow, Scotland |
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Keywords: High-Field MRI, RF Arrays & Systems, Neurovascular imaging Combined full brain and neck MRI has been proven inevitable in diagnosis of variety of neurodegenerative diseases such as multiple sclerosis, and amyotrophic lateral sclerosis. High spatial resolution and signal-to-noise ratio provided by the ultra-high field MRI systems (>7T) could be valuable in identification of such subtle morphologies which are not noticeable at standard MRI systems. Current state-of-the-art requires change of coil for imaging either brain or C-spine or equipped with 16-channel transmission capability. This work presents the design and validation of novel neurovascular transceiver array with 8 channels (industry standard) for combined head and neck imaging at 7T. |
| 4582 | Computer 163
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Slice-wise z-shimming for spinal cord fMRI with Shimming Toolbox |
| Alexandre D'Astous1, Merve Kaptan2, Daniel Papp1, Alice Dabbagh2, Jürgen Finsterbusch3, Falk Eippert2, Eva Alonso-Ortiz1, and Julien Cohen-Adad1,4,5,6 | ||
1Neuropoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada, 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 3Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, 4Mila - Quebec AI Institute, Montreal, QC, Canada, 5Functional Neuroimaging Unit, Centre de recherche de l'Institut universitaire de gériatrie de Montréal, Montreal, QC, Canada, 6Centre de recherche du CHU Sainte-Justine, Université de Montréal, Montreal, QC, Canada |
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Keywords: Shims, Spinal Cord Spinal cord fMRI is challenging, in part due to B0 inhomogeneities. An EPI, z-shimming signal intensity based approach was implemented to automatically and dynamically shim the spinal cord. The technique was implemented in the open-source Shimming Toolbox. Z-shimming was tested on a healthy participant and showed a 14% increase in signal intensity as well as 19% increase in tSNR. The technique was generalized to allow for the use of any shim coil geometry as well as non-EPI data. |
| 4583 | Computer 164
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Simulation and Comparison of Transmit Elements for 7T Head-Imaging with a Large Diameter Transmit Coil |
| Max Joris Hubmann1,2, Robert Kowal 2,3, Stephan Orzada4, Piet Wagner5, Frank Seifert5, Oliver Speck2,3, and Holger Maune2 | ||
1Siemens Healthineers GmbH, Magdeburg, Germany, 2Otto-von-Guericke University, Magdeburg, Germany, 3Research Campus STIMULATE, Magdeburg, Germany, 4Deutsches Krebsforschungszentrum Heidelberg, Heidelberg, Germany, 5Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides 12 transmission coil designs for 7T head imaging are compared using EM simulations for a large diameter transmit coil. The highest power and SAR efficiency are achieved by loop coils, a passively-fed dipole shows the highest intrinsic decoupling and an IMARS the lowest load dependence. The results provide insight to each element's performance. To make a final decision on a coil element, the array performance must also be evaluated in the futur, as this may differ from the performance of the single element performance. Thus, the decision on a particular transmit element depends on the coil's application and configuration. |
| 4584 | Computer 165
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Denoising Effect of Double-Loop Spiral Coil with ultra-High Dielectric Constant Materials for MRI Applications |
| Parisa Lotfi poshtgol1, Navid P. Gandji1, Michael Lanagan2, Soo-Han Soon3, Wei Chen3, and Qing X Yang1 | ||
1Center for NMR Research, Departments of Neurosurgery and Radiology, College of Medicine, Pennsylvania State University, Hershey, PA, United States, 2Engineering Science and Mechanics, Pennsylvania State University, state college, PA, United States, 3Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, High-Field MRI, High dielectric material We investigated the denoising effect of employing double-loop spiral coil (DLSC) versus the conventional single loop surface coil in the presence of ultrahigh dielectric constant materials (uHDCM). The DLSC confines the conservative E-field distribution between the loops which as a result reduces the E-field in the sample, therefore reduces the noise level. Reduction of conservative E-Field makes the non-conservative E-field more dominant in the sample, which synergistically with the noise reduction allows increasing transmit efficiency and receive sensitivity for MRI application. |
| 4585 | Computer 166
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Parallel transmission of cardiac imaging using statistical initial phase optimization at 5T |
| Jiaxu Li1,2, Liqiang Zhou3, Bin Liu3, Nan Li1,4, Zhenhua Shen3, Xiaoliang Zhang5, and Ye Li1,4 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 2School of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China, 3Shanghai United Imaging Healthcare, Shanghai, China, 4Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, 5Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States |
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Keywords: Parallel Transmit & Multiband, Shims High-field magnetic resonance imaging is one of the main development directions of magnetic resonance cardiac imaging because of its high signal-to-noise ratio and more anatomical details. However, with the increase of field strength, the homogeneity of B1 field is a serious challenge, and parallel transmission is one of the important methods to solve this problem.In this work, we proposed a clinically applicable radiofrequency shimming method to improve the imaging quality of cardiac imaging at 5T MRI.Statistical methods were employed to find out a better initial phase of an eight-channel coil and enhance the stability of cardiac imaging. |
| 4586 | Computer 167
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Compact 7T: Progress in Construction and Assembly of a Low-Cryogen, High-Performance, Head-only High-Field MRI System |
| Thomas Foo1, Mark Vermilyea1, Gene Conte1, Chris Van Epps1, Justin Ricci1, Minfeng Xu1, Anbo Wu1, Shike Huang1, Seung-Kyun Lee1, Wolfgang Stautner1, Bai Ye1, Doug Kelley2, John Huston III3, Matt A Bernstein3, Yunhong Shu3, Christopher Hess4, and Duan Xu4 | ||
1GE Research, Niskayuna, NY, United States, 2GE Healthcare, Waukesh, WI, United States, 3Mayo Clinic, Rochester, MN, United States, 4University of California-San Francisco, San Francisco, CA, United States |
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Keywords: High-Field MRI, Magnets (B0), Cryogenics; Low-Cryogen; Compact Steps in the construction of an 8 metric ton, 7.0 T MRI scanner for imaging the brain are described. The system nearing completion uses only 12 liters of liquid helium and has outside dimensions comparable to a clinical whole-body 3.0 T scanner, with a similar footprint. As such, the new Compact 7.0 T system fits into any whole-body 3.0 T room, simplifying installation. The system is in the final stages of assembly. |
| 4587 | Computer 168
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Improved multi-channel pTx B1+ mapping in the head and neck at 7T by combining RF shims and transmit voltages |
| Matthijs H.S. de Buck1, Peter Jezzard1, and Aaron T. Hess1 | ||
1Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom |
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Keywords: Parallel Transmit & Multiband, High-Field MRI, B1+ mapping Acquiring robust multi-channel B1+ maps in both the head and neck using pTx head coils at 7T can be challenging due to the combination of low RF penetration into the neck, the limited dynamic range of multi-channel B1+ mapping techniques, and B0 sensitivity. We present a pipeline for large dynamic range pTx field mapping along with a publicly available 10-subject database of head and neck field maps for a commonly used multi-channel head transmit coil. The pipeline is evaluated by comparing the predicted B1+ to the measured B1+ for random transmit shim configurations in the head and neck. |
| 4588 | Computer 169
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Susceptibility-weighted imaging (SWI) of the kidney at 5T – initial results |
| Liyun Zheng1,2,3, Chun Yang1,2, Yongming Dai4, and Mengsu Zeng1,2 | ||
1Shanghai Institute of Medical Imaging, Shanghai, China, 2Department of Radiology, Zhongshan Hospital, Fudan University, Shanghai, China, 3Shenzhen United Imaging Research Institute of Innovative Medical Equipment, Shenzhen, China, 4MR Collaboration, Central Research Institute, United Imaging Healthcare, Shanghai, China |
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Keywords: High-Field MRI, Kidney At high magnetic field strengths (B0 ≥ 3 T), susceptibility-weighted imaging (SWI) is an appealing approach for increased signal-to-noise ratio (SNR). To our knowledge, implementation of SWI on the kidney at higher field MRI (> 3T) has not been attempted yet. This initial study proved that it is possible to obtain SWI at 5T for renal with sufficient image quality. For 5T SWI, SNR of cortex and medulla and CNR of cortex/medulla were significantly higher than at 3T, leading to improved vessel conspicuity and corticomedullary discrimination. |
| 4589 | Computer 170
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16-Channel 11.7T Transmit Array with Integrated Field Probes |
| Son Chu1, Vincent Gras2, Nicolas Boulant2, and Shajan Gunamony1 | ||
1University of Glasgow, Glasgow, United Kingdom, 2University of Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif sur Yvette, France |
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Keywords: RF Arrays & Systems, RF Arrays & Systems Transmit arrays are essential to mitigate B1+ inhomogeneity at extremely high static magnetic field strengths. In addition, the transmit elements must be arranged in multiple rows to achieve whole-brain coverage at 11.7T. Furthermore, concurrent field monitoring probes offer the possibility to improve MR image quality by correcting subject-specific k-space trajectories and monitoring real-time dynamic field fluctuations. The placement of these probes must be carefully controlled to achieve proper probe conditioning as well as to preserve the RF performance of the transmit array. This work presents the numerical simulation and optimization of a 16-channel-transmit array with integrated field probes. |
| 4590 | Computer 171
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Reproducibility and variability of tailored and universal nonselective excitation pulses at 7T for human body imaging: Re-scans after one year |
| Christoph Stefan Aigner1, Jean Pierre Bassenge1,2, Sebastian Dietrich1, Max Lutz1, Felix Krüger1, and Sebastian Schmitter1,3,4 | ||
1Physikalisch-Technische Bundesanstalt (PTB), Berlin and Braunschweig, Germany, 2Working Group on Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine, Berlin, Germany, 3Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 4University of Minnesota, Center for Magnetic Resonance Research, Minneapolis, MN, United States |
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Keywords: RF Pulse Design & Fields, Parallel Transmit & Multiband 3D ultrahigh field (UHF) imaging of the body, particularly the heart, is highly challenging due to the inhomogeneous transmit field (B1+) leading to spatially varying flip-angle (FA) patterns. This study demonstrates that pre-computed universal pulses (UPs) allow for calibration-free 3D cardiac FA homogenization at 7T, despite inter-subject variations because of sex, age, BMI, and coil-placement differences. Furthermore, the performance is robust across multiple MRI operators or re-scans after one year. UPs are, therefore, suited to significantly simplify UHF cardiac imaging by removing the need for lengthy calibration prescans. |
| 4591 | Computer 172
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A Comparison Between Shielded and Unshielded RF Antennas for 7T Body MRI |
| Tobey D Haluptzok1, Simon Schmidt1, Russell L Lagore1, and Gregory J Metzger1 | ||
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States |
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Keywords: RF Arrays & Systems, High-Field MRI To more fully realize the benefit of UHF MRI, coil designs must be optimized to for pTx and intrinsic SNR performance. In this abstract we compare 5 RF coil array block systems. The first comparison ran is pTx performance, the second comparison is of intrinsic array SNR, and the third tests robustness to top loading. The shielded and unshielded three-loop dipole elements performed better than the single-loop dipole and the shieled helped with top load insensitivity. From these results we conclude that the three-loop dipole coil blocks have superior performance and that the shield doesn’t hurt performance. |
| 4592 | Computer 173
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PASTeUR package extension to slab-selective excitations and 3D-EPI for plug-and-play parallel transmit at 7 Tesla |
| Redouane Jamil1, Aurélien Massire2, Franck Mauconduit1, Vincent Gras1, Mathieu Naudin3,4,5, Rémy Guillevin3,4,5, Eberhard Pracht6, Tony Stöcker6,7, Nicolas Boulant1, and Rüdiger Stirnberg6 | ||
1Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, 2Siemens Healthcare SAS, Saint-Denis, France, 3CHU Poitiers, Poitiers, France, 4LRCOM I3M, DACTIM LMA CNRS 7348, University of Poitiers, Poitiers, France, 5Laboratory of Applied Mathematics, UMR CNRS 7348, University of Poitiers, Poitiers, France, 6German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, 7Department of Physics and Astronomy, University of Bonn, Bonn, Germany |
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Keywords: Parallel Transmit & Multiband, Parallel Transmit & Multiband, High-Field MRI; fMRI Keywords: Parallel Transmit & Multiband; High-Field MRI; RF Pulse Design & Fields; fMRI PASTeUR is a package of sequences using non-selective parallel transmission Universal Pulses (UP) as a plug-and-play pTX solution alleviating B1+ inhomogeneities. Here, we extend the UP solution to slab-selective excitations while preserving a plug-and-play philosophy. A slab of any thickness/orientation/rotation can be acquired without subject-specific calibrations. In vivo experiments performed with an fMRI protocol on a 3D-EPI show that the improved B1+ homogeneity can result in higher SNR. Moreover, the slab-selective UP coupled with parallel imaging and segmented k-space acquisitions pushed further the quality of 3D-EPI. |
| 4593 | Computer 174
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Design and Test of a Flexible Two-row CTL Array and Its Detunable Resonant Elements for 10.5T MR Imaging |
| Xiaoliang Zhang1, Matt Waks2, Lance DelaBarre2, Komlan Payne1, Kamil Ugurbil2, and Gregor Adriany2 | ||
1Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States, 2Radiology, University of Minnesota, Minneapolis, MN, United States |
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Keywords: New Devices, High-Field MRI A flexible patch array using small-sized 5-cm coaxial transmission line (CTL) resonators is designed, constructed and tested, aiming for human head imaging at the ultrahigh field of 10.5T. Bench tests on decoupling performance among resonant elements are shown. For full utility, a detuning circuit is successfully developed, showing the ecellent detuning capability for 5-cm small CTL loops at 447 MHz. This study suggests that it is possible to build high-density receive-only coil arrays using small-sized CTL resonators at 10.5T. |
| 4594 | Computer 175
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Impact of a High-Permittivity Helmet on Transmit Efficiency Across a Wide Range of Field Strengths and Relative Permittivities |
| Giuseppe Carluccio1,2 and Christopher Michael Collins1,2 | ||
1Radiology, NYU Grossman School of Medicine, New York, NY, United States, 2Center for Advanced Imaging Innovation and Research (CAI2R), New York University, New York, NY, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, High-Permittivity Materials High-Permittivity Materials are used in MRI to manipulate the B1 field distribution for example to provide a stronger transmit efficiency. For a given coil, the transmit efficiency depends on the frequency. Here we examine the effects of a high-permittivity helmet on the transmit efficiency in exciting the brain with a birdcage coil over a range of frequencies. The optimal frequency providing the maximum transmit efficiency is not significantly impacted by the presence of the helmet, while the maximum efficiency can increase by about 100% compared to when no helmet is used. |
| 4595 | Computer 176
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Metasurface for passive RF shimming to improve brain imaging at 7T |
| Vladislav Koloskov1, Alena Shchelokova1, and Andrew Webb2 | ||
1School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation, 2Department of Radiology, C.J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands |
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Keywords: Hybrid & Novel Systems Technology, Hybrid & Novel Systems Technology, metasurface, passive shimming We propose a new passive radiofrequency (RF) shimming approach using a flexible, compact, low-cost, and long-term stability metasurface to improve brain imaging at 7T. The metasurface can be manufactured as a periodic structure based on a set of metal crosses connected by the capacitors, thus having a thickness of less than 1 mm. Numerical studies with the human voxel model showed up to 6% homogeneity improvement at the regions of interest (ROI) in the presence of the metasurface in comparison with the conventional case, which also outperforms the effect of the dielectric pad’s placement. |
| 5063 | Computer 121
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Low-Loss Switches for Multinuclear MRI/S Using Stimuli-Responsive Polymer Materials |
| Edith Valle1, Seelay Tasmim2, Mary P. McDougall1,2, and Taylor H. Ware2,3 | ||
1Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States, 2Biomedical Engineering, Texas A&M University, College Station, TX, United States, 3Materials Science & Engineering, Texas A&M University, College Station, TX, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Hybrid & Novel Systems Technology The development of highly sensitive multinuclear RF coils for MRI/S is challenging because most current multi-tuning techniques involve the addition of lossy components. Although it is possible to optimize for a particular nucleus, usually non-1H, multinuclear coils have lower SNR than their single-tuned counterparts. We investigate a novel switching system that uses stimuli-responsive materials. The coils with the proposed switching method had a decrease of <26% in Q when compared to single-tuned coils. As a result, we demonstrated a promising alternative to traditional switching techniques. |
| 5064 | Computer 122
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Investigation of Triple-Tuned Trap Designs |
| Joseph Busher1 and Mary P. McDougall1,2 | ||
1Biomedical Engineering, Texas A&M University, College Station, TX, United States, 2Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides Multi-frequency coils are typically known to have substantial losses as compared to their single-tuned counterparts. Here we investigate sensitivity tradeoffs of triple-tuned (1H-23Na-31P) trap designs on receive coils in a tightly controlled experiment to isolate the sensitivity effects of the traps. Triple-tuned LCC traps were shown to have significant improvement in sensitivity for 23Na and 1H as compared to an LC trap design. The increase came at the expense of 31P sensitivity, however continued optimization of the trap design will likely further improve the final experimental SNR. |
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A Triple-nuclear four-channel RF coil for Simultaneous acquisition of 1H/19F/23Na MR imaging at 3T |
| Nan Li1,2, Feng Du1,2, Xiaoliang Zhang3, Xin Liu1,2, Hairong Zheng1,2, and Ye Li1,2 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, Shenzhen, China, 3Department of Biomedical Engineering, State University of New York, Buffalo, NY, United States, Buffalo, NY, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems As the lower natural abundance of X-nuclei, it is important to enhance that the signal-to-noise ratio (SNR) of the X-nuclei is as high as possible by designing a well-designed multiple-tuned coils. In this study, a new triple-tuned RF coil system capable of 1H / 19F / 23Na imaging was proposed. The performance of the triple-tuned coil was evaluated compared to their counterpart single-tuned coils by the numerical electromagnetic simulation. Imaging tests at 3T MRI were performed on the phantom by using the triple-tuned RF coil. |
| 5066 | Computer 124
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Signal-to-noise and B1 characterization of linear and quadrature 13C-cryocoils for preclinical MRSI |
| Luca Nagel1, Geoffrey J. Topping1, and Franz Schilling1 | ||
1School of Medicine, Klinikum rechts der Isar, Department of Nuclear Medicine, Technical University of Munich (TUM),, Munich, Germany |
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Keywords: RF Arrays & Systems, RF Arrays & Systems Cryogenically-cooled 13C radiofrequency (RF) coils (cryocoils) improve SNR by reducing thermal coil noise compared to room-temperature coils. Coil geometry impacts B1 patterns, which impact experiment design and must be characterized. The sensitivity profiles of a linear and a quadrature coil were characterized with varied RF powers, which is complicated by transmit B1 variation with position and resulting excitation variations. The sensitivity was compared to a room-temperature volume resonator. The quadrature cryocoil configuration offers better B1 uniformity but lower SNR closest to the coil compared to the linear configuration, both have an overall better SNR performance compared to the volume resonator. |
| 5067 | Computer 125
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Investigating Dipole Antennas as 1H Transmit Elements for a 1H/31P Calf Coil at 7 T |
| Veronika Cap1, Martin Meyerspeer1, Sigrun Roat1, Elmar Laistler1, and Roberta Frass-Kriegl1 | ||
1Division MR Physics, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria |
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Keywords: RF Arrays & Systems, RF Arrays & Systems, dipoles, simulation Different dipole antenna types as 1H transmit elements for metabolic 1H/31P MRS studies of the human calf were investigated. In simulations, the dipole elements and a loop coil were compared in terms of transmit efficiency and SAR. A three-element array of the best-performing design was simulated and constructed, and its transmit performance was found to be comparable to a four-element loop array. Investigating the interaction between a dipole transmit element and a receive-only loop placed underneath, efficient geometric decoupling was observed. This can be exploited to improve the receive sensitivity (homogeneity, depth) by using transceiver dipoles together with receive-only loops. |
| 5068 | Computer 126
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Design and Construction of a quadruple-nuclear transceiver coil array for 1H/19F/23Na/31P MRI at 3T |
| Feng Du1,2, Nan Li1,2, Xiaoliang Zhang3, Xin Liu1,2, Hairong Zheng1,2, and Ye Li1,2 | ||
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen 518055, Guang Dong, China, Shenzhen, China, 3Department of Biomedical Engineering, State University of New York, Buffalo, NY, United States, Buffalo, NY, United States |
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Keywords: RF Arrays & Systems, New Devices Multinuclear MRI has been demonstrated as a crucial tool for comprehensively characterizing tumor pathology and monitoring tumor treatment response as it can provide biochemical, physical, and functional as well as structural information. The objective of this work is to develop a quadruple-nuclear transceiver coil array for 1H/19F/23Na/31P MRI at 3T to simultaneously detect multinucleal signals. The phantom studies were performed on self-developed 3T MRI system to verify the performance. These results proved that uniform excitation and highly sensitive acquisition in the region of interest were achieved by utilizing the proposed RF coil and indicated the fesibility for multinuclear MRI applications. |
| 5069 | Computer 127
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A Low-complexity Approach to Decouple Dual-tuned RF Coil Elements in Multinuclear Receive Array Coils |
| Chenhao Sun1, Courtney Bauer1, Jue Hou1, and Steven M. Wright1 | ||
1Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems, Multi-Nuclei, multinuclear, decoupling This study proposes a novel low-complexity decoupling approach for multi-nuclei receive array coil design. Instead of using narrowband LC networks and isolation preamplifiers, a preamplifier with high input impedance can be used to decouple receive coils while maintaining most SNR. A broadband impedance matching network consist of LCC multi-tuned circuit and transformer was developed to interface the coil with a high Z preamplifier. The proposed setup has achieved more than 15dB of decoupling over a range of 25MHz. The prototype simultaneously yielded 73.6% and 91.9% of SNR at 2H and 23Na when compared to the conventional single-tuned preamplifier decoupling methods. |
| 5070 | Computer 128
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Reconfigurable Coaxial Receive Dipoles for Dynamic Parallel Imaging of Human Brain at 9.4T |
| Georgiy Alekseevich Solomakha1, Felix Glang1, Theodor Steffen2, Klaus Scheffler1,3, and Nikolai Ivanovich Avdievich 1 | ||
1High-field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, 2Electronical Workshop, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, 3Department for Biomedical Magnetic Resonance, University of Tübingen, Tuebingen, Germany |
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Keywords: RF Arrays & Systems, RF Arrays & Systems Recently developed dynamic parallel imaging, i.e. rapid modulation of element's sensitivities during acquisition, greatly improved the performance of the method. In this work, sensitivity profiles of dipole elements were electronically reconfigured by varying impedances of lumped element circuits connected in series with the dipoles . This required a large number of DC wires directly connected to the dipoles. In the present work, we developed, constructed, and evaluated a dynamically reconfigurable 8-element coaxial dipole array for brain imaging at 9.4T. Our design eliminates the DC wires directly connected to the dipoles and, hence, substantially simplifies further increasing the number of receive channels. |
| 5071 | Computer 129
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A high impedance radio-frequency system improves the decoupling between receiving coils in MRI |
| Yu-Lung Tang1, Hsin-Ju Lee2,3, and Fa-Hsuan Lin2,3 | ||
1Timwave Technologies Company Limited, Taipei, Taiwan, 2Sunnybrook Research Institute, Toronto, ON, Canada, 3University of Toronto, Toronto, ON, Canada |
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Keywords: RF Arrays & Systems, RF Arrays & Systems The decoupling between coils significantly impacts the amount of independent information between channels in a receiver coil array. Using a pre-amplifier with a low input impedance is limited by the technology in achieving the lowest possible impedance, typically around a few ohms. Here we propose a strategy to improve the decoupling between coil elements in a receiver array by increasing the impedance of the coil system. Simulations and bench measurements show that increasing the impedance from a typical 50 ohm to around 1,000 ohm can increase the decoupling by 25 dB. |
| 5072 | Computer 130
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Dielectric Loaded Stretchable and Flexible Surface RF Coil |
| Seyedamin Hashemi1, Sri Kirthi Kandala1, and Sung-Min Sohn1 | ||
1School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States |
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Keywords: RF Arrays & Systems, Phantoms, Receive coil, flexible coil, loaded coil This study presents a novel receive radiofrequency coil that enhances the signal-to-noise-ratio (SNR) and field-of-view (FOV) in magnetic resonance images. The fabricated coil is loaded by a mixture of dielectric material (TiO2) and an elastomer offering stretchability and flexibility. The functionality of the coil compared to a typical surface coil was assessed using phantom imaging at 7T. The SNR (in dB), signal intensity, and uniformity are improved by 14.75%, 25%, and 87.76% by using a TiO2-loaded coil, respectively. This design method will be invaluable for uneven sample shapes and a very close place to a subject. |
| 5073 | Computer 131
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Helmet RF Applicator for Enhancing Focal RF Power Deposition in Thermal Magnetic Resonance of the Brain at 7T |
| Faezeh Rahimi1,2, Thomas Wilhelm Eigentler1,3, Jason M. Millward1,4, Pirus Ghadjar5, and Thoralf Niendorf1,4,6 | ||
1Berlin Ultrahigh Field Facility, Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, 2Theoretische Elektrotechnik Institut Hochfrequenz- und Halbleiter-Systemtechnologien, Technische Universität Berlin, Berlin, Germany, 3Chair of Medical Engineering, Technische Universität Berlin, Berlin, Germany, 4a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine, Berlin, Germany, 5Clinic for Radiation Oncology, Charite’ Universitätsmedizin, Berlin, Germany, 6MRI.TOOLS GmbH, Berlin, Germany |
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Keywords: RF Arrays & Systems, Interventional Devices, SAR distribution, Focal Heating, Hyperthermia, Brain Thermal MR at 7T Thermal Magnetic Resonance (ThermalMR) uses an RF-applicator to add a thermal intervention dimension to a diagnostic imaging device. Optimizing the performance of RF applicator configurations can eventually improve the performance of ThemalMR. This work examines the feasibility of multi-channel RF applicators using broadband Self-Grounded Bow-Tie (SGBT) antenna building blocks. The focus is on enhancing focal RF power deposition in a target volume by using a multi-channel helmet RF array configuration versus conventional annular RF arrays. Our preliminary findings obtained for the human head voxel model Duke show improved target coverage of high SAR10g and high temperature for the helmet configuration. |
| 5074 | Computer 132
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Overlapped or gapped multi-row self-decoupled transmit array: which is better? |
| Ming Lu1, Zhipeng Cao2,3, and Xinqiang Yan2,3 | ||
1College of Nuclear Equipment and Nuclear Engineering, Yantai University, Yantai, China, 2Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, 3Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States |
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Keywords: Parallel Transmit & Multiband, High-Field MRI This work is aiming to answer which multi-row self-decoupled array outperforms in parallel transmission to generate a uniform transmit RF field (B1+). |
| 5075 | Computer 133
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Xenon-129 Platform for Operating a T/R Coil and Phased Array at 3T |
| Wolfgang Loew1, Virginia Van Horne2, Peter van der Meulen3, and Charles Dumoulin1 | ||
1Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States, 2Innovation Ventures, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States, 3Philips Healthcare, Best, Netherlands |
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Keywords: Whole Body, New Devices A platform was developed for 129Xe applications allowing the use of an insertable whole-body transmit/receive coil by itself or in combination with a 129Xe phased array coil. Experiments were performed in a 3T MRI scanner without modification of the scanner’s 1H body coil. 129Xe imaging was performed with a loader phantom and a xenon Boltzmann phantom in both configurations. |
| 5076 | Computer 134
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The Lord of the EndRings: A roadmap for the design and construction of a Tx/Rx 31P birdcage head coil and feed network at 3 Tesla |
| Peter Truong1, Helmut Stark2, Agessandro Abraham3,4, Lorne Zinman3,5, and Jamie Near1,6 | ||
1Physical Sciences Research Platform, Hurvitz Brain Sciences Program, Sunnybrook Research Institute, Toronto, ON, Canada, 2Stark Contrast, Erlangden, Germany, 3Evaluative Clinical Sciences, Hurvitz Brain Sciences Research Program, Sunnybrook Research Institute, Toronto, ON, Canada, 4Department of Medicine (Neurology), Sunnybrook Health Sciences Centre and University of Toronto, Toronto, ON, Canada, 5Institute of Medical Science and Rehabilitation Sciences Institute, University of Toronto, Toronto, ON, Canada, 6Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Challenges Join us as we take you on a journey in the development of a Tx/Rx 31P birdcage head coil. Even though there is a wealth of available knowledge explaining the theory of MRI RF coil design, there are many unforeseen situations one will encounter in practice. The road for coil development is filled with many valuable lessons. We hope to provide a practical guide for new builders by describing our experiences in coil design, construction, and troubleshooting. |
| 5077 | Computer 135
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DOuble tuned and DOuble matched large-size loop coil (DODO) design and evaluation for 17O MRSI and 1H MRI application at 7T |
| Xin Li1, Guangle Zhang1, Wei Zhu1, Xiaoliang Zhang2, Xiao-Hong Zhu1, and Wei Chen1 | ||
1Department of Radiology, University of Minnesota, Minneapolis, MN, United States, 2School of Engineering and Applied Sciences, University of Buffalo, Buffalo, NY, United States |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, RF Arrays & Systems Current state-of-the-art RF coils for X-nuclear MRS/MRI studies typically use two separate sets of RF coils operating at the X-nuclear and proton frequencies, respectively. Here, we introduce a new coil concept whereby large-size loop coil with split capacitors which can be simultaneously tuned and matched to 17O and 1H Larmor frequencies for 7T human imaging application. Importantly, this novel coil exhibits excellent performance in proton and X-nuclear imaging, therefore, it provides a simple RF coil solution, particularly for ultrahigh field (UHF) multinuclear brain MR imaging applications. |
| 5078 | Computer 136
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Wearable and stretchable RF coils using self-decoupling technology |
| Shuyang Chai1,2, John Gore1,2, and Xinqiang Yan1,2 | ||
1Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, 2Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States |
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Keywords: RF Arrays & Systems, RF Arrays & Systems A novel flexible and stretchable coil based on the self-decoupling technology is proposed. It can be stretched and bent to match the shape of the human anatomy of interest, exhibiting high SNR. A 4 coil array was built and tested at different stretching (horizontally and vertically), and on different anatomies (torse, thigh, head), showing a strong robustness. |
| 5079 | Computer 137
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A multi-feed, loop-dipole approach to enhance performance of multi-channel dielectric resonator antenna arrays for human brain MRI at 7T |
| Daniel Wenz1,2 and Thomas Dardano1,2 | ||
1CIBM Center for Biomedical Imaging, Lausanne, Switzerland, 2Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Dielectric resonator, loo-dipole The goal of this work was to demonstrate that performance of multi-channel dielectric resonator antenna arrays for brain MRI at 7T can be substantially improved using a novel multi-feed, loop-dipole coupling mechanism. Simulations were conducted for different rectangular DRA geometries and dielectric constants. Three RF feed types were investigated: loop-only, dipole-only and loop-dipole. 16-channel, loop-dipole rectangular DRA arrays provided significant gains in B1+, SAR efficiency and SNR vs. 8-channel bow-tie antenna array. The feasibility of multi-feed, loop-dipole approach was for a 24-channel DRA array was demonstrated. |
| 5080 | Computer 138
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A 16-Channel Proton/Sodium Transmit/Receive Array Design for 7 Tesla Head Imaging |
| Menglu Wu1,2, Jérémie Clément1,3, Jules Vliem1,4, David Leitão 1, Raphael Tomi-Tricot1,2,5, and Özlem Ipek1,2 | ||
1Biomedical Engineering, King's College London, London, United Kingdom, 2London Collaborative Ultra high field System (LoCUS), King's College London, London, United Kingdom, 3System Technologies, Siemens Healthcare GmbH, Erlangen, Germany, 4Electrical Engineering, Technical University of Eindhoven, Eindhoven, Netherlands, 5MR Research Collaborations, Siemens Healthineers, Frimley, United Kingdom |
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Keywords: RF Arrays & Systems, Non-Proton 7T MRI has great potential to enhance the sensitivity to 23Na, allowing access to functional and anatomical information when combined with proton imaging. We introduce an RF coil design of a 16-channel Tx/Rx head array composed of eight proton dipoles and eight overlapping sodium loops for 7T. The initial results were acquired on phantoms with comparable performance for both nuclei, and a 40% B1+ gain was reported in sodium channels against the commercial coil. All elements were well-decoupled (-7.2dB to -36dB) without implementation of multiple layers or RF shield, paving the way for future simultaneous 1H/23Na MRI acquisition at 7T. |
| 5081 | Computer 139
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High-density dipole array for human lumbar spine cord imaging at 7T |
| Ming Lu1, Shuyang Chai2,3, and Xinqiang Yan2,3 | ||
1College of Nuclear Equipment and Nuclear Engineering, Yantai University, Yantai, China, 2Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, 3Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States |
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Keywords: RF Arrays & Systems, High-Field MRI The Dipole antenna, which has a long longitudinal coverage and deep penetration, has demonstrated a better transmit efficiency for spinal cord imaging compared to the standard loop coil. However, owing to the inevitable coupling, the number of dipoles is highly limited. In this work, we find that the number of dipoles could be doubled if they are be shortened in different ways and arranged to interleave. An 8-channel dipole array consisting of 4 inductor-shortened dipoles and 4 folded dipoles was designed and numerically investigated for 7T lumbar spinal cord imaging. |
| 5082 | Computer 140
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First MR Images acquisition with decoupled High Temperature Superconducting surface coils |
| Camille Dubuc1,2, Aimé Labbé1, Sina Marhabaie1, Clément Thibault3,4, Jean-Christophe Ginefri1, Javier Briatico5, and Marie Poirier-Quinot1 | ||
1Université Paris-Saclay, BioMaps, ORSAY, France, 2Thales Research & Technology, Palaiseau, France, 3Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France, 4Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, 5Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France |
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Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Superconducting material, Decoupling A promising strategy to tackle the issue of decoupling High-Temperature Superconducting (HTS) surface coils during emission is to exploit nonlinearities of the HTS coil electromagnetic response. In this work, we present the first Magnetic Resonance Images acquired with a decoupled HTS surface coil and the required coil’s features to obtain these images. The change of the HTS coil Q-factor values leads to different decoupling levels (DL) of the HTS coil and the presence or absence of B1 artifacts on the images. |
| 5219 | Computer 121
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Gradient Non-Linearity Calibration for Improved Spatial Position Accuracy with a High-Performance Gradient Using a Fiducial Phantom |
| Nastaren Abad1, Eric Fiveland1, Seung-Kyun Lee1, Yihe Hua1, Shengzhen Tao2, Joshua Trazasko3, Matt A. Bernstein3, and Thomas K.F Foo1 | ||
1GE Research, Niskayuna, NY, United States, 2Mayo Clinic, Jacksonville, FL, United States, 3Mayo Clinic, Rochester, MN, United States |
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Keywords: System Imperfections: Measurement & Correction, System Imperfections: Measurement & Correction, Gradient Non-Linearity; Spatial Fidelity; High Performance Gradients Spatial encoding in MR-systems is subject to gradient non-linearity. If ignored or inadequately calibrated during system install, non-linear gradient fields manifest as spatial distortions impacting image quality, diminish accuracy for applications requiring MR guided intervention and introduce systematic errors in quantitative imaging such as diffusion MRI. High-performance, high-efficiency gradient systems, such as MAGNUS, require accurate calibration for imaging precision. In this study, a fiducial phantom was utilized to characterize and correct for residual distortions after standard gradient calibrations. Results highlight that distortion due to gradient non-linearity can be successfully reduced by phantom-based calibration for improved accuracy inline with QC metrics. |
| 5220 | Computer 122
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Development of a realistic human spine phantom to mimic static B0 field inhomogeneity in the cervical spinal cord |
| Brunnhilde M, A-S Ponsi1, Laura Beghini1, Sebastian A.D Sandbu1, Annelen Dogger Schmidt1, and S. Johanna Vannesjo1 | ||
1Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway |
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Keywords: Phantoms, Spinal Cord, Susceptibility, Field inhomogeneity, High field MRI, Shims, Artifacts, Field simulation Anthropomorphic phantoms could facilitate testing of novel MRI methods. This is especially important for spinal cord imaging at 7T, which is severely affected by local B0 field inhomogeneity due to susceptibility differences between tissues, particularly between bone and soft tissues. Here we built a 3D-printed model of vertebrae C3-C5, which was included in a spherical phantom. Measured field maps of the phantom were compared with simulations, showing similar features in the field distortion. The phantom also exhibited a spatially periodic pattern of signal drop-out around the intervertebral junctions in multi-echo GRE, similar to what is commonly observed in in-vivo data. |
| 5221 | Computer 123
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Realistic human head phantoms for 7T sequence development, parallel transmission & spectroscopy methodology |
| Sascha Brunheim1, Yannik Völzke1, Astrid Dubbins1, Eberhard D. Pracht1, and Tony Stöcker1,2 | ||
1German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, 2Physics and Astronomy, University of Bonn, Bonn, Germany |
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Keywords: Phantoms, RF Pulse Design & Fields, Spectroscopy An optimized human head phantom design for 7 Tesla field strength and its standardized fabrication process is presented. Two different phantom versions were produced: The first gel-only version can be set up quickly and provided realistic T1 and T2 values for its brain, muscle, and lipid compartments. The second version, with its liquid brain compartment containing several metabolites, can be utilized for spectroscopy sequence development. With the 3D model and the validated recipes mimicking head and brain tissue, extensions to other applications can be more easily achieved, such as system characterization, diffusion weighted imaging, or realistic flow phantoms. |
| 5222 | Computer 124
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Design and Production of a 3D Printed Anthropomorphic Head Phantom for MRI – The Story so Far |
| George Michael John Bruce1,2, Pauline Hall-Barrientos1,2, and David Brennan1,2 | ||
1MRI Physics, Department of Clinical Physics and Bioengineering, NHS Greater Glasgow and Clyde, Glasgow, United Kingdom, 2School of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom |
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Keywords: Phantoms, Phantoms, 3D Printing Commercial phantom objects for use in MR can be expensive and poorly representative of human anatomy. 3D printing provides the potential to produce cheaper, novel and reproducible phantoms . This project investigates the potential use of 3D printed materials in the construction of an anthropomorphic head phantom for MRI. It can be effectively split into two different, smaller projects: investigation into MR properties of 3D printed materials and design of an anthropomorphic head phantom for MRI. |
| 5223 | Computer 125
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Design and Validation of a Multi-Modality Lung Phantom |
| Donald L Bowen1, Tyler J Touchet1, Duncan J Maitland1, and Mary P McDougall2 | ||
1Biomedical Engineering, Texas A&M University, College Station, TX, United States, 2Biomedical Engineering and Electrical Engineering, Texas A&M University, College Station, TX, United States |
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Keywords: Phantoms, Multimodal Phantoms often mimic only one specific property of the body, and without relevant anatomical structure. We report the design and construction of an anatomic phantom that accurately mimics the in vivo properties of the lungs for both ultrasound and magnetic resonance imaging. The phantom demonstrated qualitative likeness to the lungs under ultrasound and quantitatively similar tissue relaxation characteristics using magnetic resonance imaging. Future work will determine if the phantom can be used to validate early-stage medical devices that operate within the lungs. |
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A Pre-Prepared, Low-Cost, Mass-Produced Phantom Regulated by the Food Standards Agency for Assessing Imaging Characteristics within MRI |
| Aaron Axford1, Jordan McGing1, Catarina Rua2, Mark Symms3, Damian J Tyler1,4, and James T Grist1,4,5,6,7 | ||
1Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, United Kingdom, 2Invicro LLC, London, United Kingdom, 3GE Healthcare, London, United Kingdom, 4Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, United Kingdom, 5Department of Radiology, Oxford University Hospitals, Oxford, United Kingdom, 6Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom, 7University of Bologna, Bologna, Italy |
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Keywords: Phantoms, Relaxometry A potential low-cost quantitative MR image assessment phantom was investigated by calculating relaxation times and the magnetization transfer ratio over multiple scans. An imaging protocol comprised of an inversion recovery sequence with varying inversion times, a spin echo with varying echo times, and an Enhanced Fast Gradient Echo 3D sequence with and without a magnetization transfer pulse, was developed and used to acquire images of the phantom, a block of store-bought jelly. The imaging data was used to calculate a T1 time of 109±1ms, a T2 time of 12.8±0.2ms, and an MTR value of 17.4±0.2%. |
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Do anthropomorphic phantoms enhance compliance with the professional bodies' quality assurance guidelines for MRI in radiotherapy |
| Meshal Alzahrani1,2, David Broadbent3, Irvin Teh1, Bashar Al-Qaisieh3, Adrian Walker4, Rachel Lamb4, and Richard Speight3 | ||
1Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom, 2Department of Diagnostic Radiology, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia, 3Department of Medical Physics and Engineering, Leeds Teaching Hospitals NHS Trust, Leeds, United Kingdom, 4Leeds Test Objects, Boroughbridge, United Kingdom |
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Keywords: Phantoms, Radiotherapy With the increasing use of magnetic resonance imaging (MRI) in radiotherapy (RT), guidelines for the use of MRI in RT have recently been published, including recommendations for quality assurance (QA) tests. This project investigates whether anthropomorphic phantoms can be more beneficial to comply with these guidelines compared to other phantoms. The performance of the anthropomorphic phantom has been compared to other phantoms. The anthropomorphic phantom has been shown to be useful in QA for MRI-CT registration and end-to-end test that cannot be performed by other phantoms. |
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Assessing Scanner Changes after Major Repairs using Traceable Phantoms from the NIST/NIBIB Lending Library |
| Stephen E Russek1, Kathryn E Keenan1, Karl F Stupic1, Cassandra M Stoffer1, Teryn S Wilkes2, and Lena Sherbakov2 | ||
1NIST, Boulder, CO, United States, 2Intermountain Neuroimaging Consortium, University of Colorado, Boulder, CO, United States |
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Keywords: System Imperfections: Measurement & Correction, Quantitative Imaging We demonstrate the utility of periodic use of standard phantoms to assess changes in MRI scanner performance after unexpected major repairs. We present characterization of a 3T scanner before and after an unexpected gradient failure and replacement using a traceable system phantom and an isotropic diffusion phantom from the NIST/NIBIB Medical Phantom Lending Library. No major changes were observed in gradient calibration, geometric distortion, imaging uniformity, and resolution. Post-repair improvements were noted in SNR, relaxation time, water diffusivity measurements, although both pre and post-repair data were acceptable. |
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UV-Curable Hydrogels for Quantitative T1/T2 in Slice Phantoms |
| Szu Ting Tung1, Jolene Huey1, Michael Lustig 1, Ana Claudia Arias1, and Anita Flynn1 | ||
1Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA, United States |
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Keywords: Phantoms, Multi-Contrast We developed a high-volume, low error UV-curable hydrogel formation process that can target specific T1 and T2 parameters. Our process relies on the polymerization of water-soluble photoinitiator TPO-Lithium in acrylamide (monomer), polyethylene-glycol-diacrylate (crosslinker), de-ionized (DI) water, and paramagnetic ions. We characterize the linearizing effect of varying paramagnetic ion concentrations in determining T1 and T2 values, and present an application to construct a quantitative anatomy-mimicking brain slice phantom containing UV gels. |
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Development of an easy-manufacturable and cheap phantom for quality control of T1, T2 and fat fraction mapping. |
| Laurence Dallet1, Sylvain Miraux1, François Maingault1, and Emeline J Ribot1 | ||
1Centre de Résonance Magnétiques des Systèmes biologiques UMR5536, CNRS/Université de Bordeaux, Bordeaux, France |
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Keywords: Phantoms, Quantitative Imaging, quality control A quality control phantom was developed through a simple and easy protocol for T1, T2 and Fat fraction mapping. The phantom is constituted of 8 tubes containing Gd-DOTA or commercially available animal fat, each at various concentrations and stabilized in agarose gels. A 3D printed bubble trap was placed on top of the gels to limit the contrast agent dilution over time. The solutions are stable for at least 6 months and the manufacturing protocol is highly reproducible. |
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Imaging-Based Subject-Specific SAR Maps using B1-mapping and Electrical Properties Tomography in a heterogenous Brain Phantom |
| Jessica A. Martinez1, Adriano Troia1, Alessandro Arduino1, Kevin Moulin2,3, Umberto Zanovello1, Oriano Bottauscio1, and Luca Zilberti1 | ||
1Advanced Materials Metrology and Life Science, Istituto Nazionale di Ricerca Metrologica, Torino, Italy, 2CREATIS Laboratory, University of Lyon, Lyon, France, 3Department of Radiology, University Hospital Saint-Etienne, Saint-Etienne, France |
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Keywords: Safety, Safety, Specific Absorption Rate, SAR In this work a heterogeneous realistic brain phantom, with electric and magnetic properties in the range of healthy gray-matter and white-matter, was constructed. The phantom was scanned at 3 T where T1 maps, T2 maps, magnitude, and phase information of the B1 field were acquired. The electrical conductivity was derived using a convection reaction EPT approach and the E field was obtained by solving Ampere’s law from the B1 field. From this information, imaging-based subject-specific SAR maps were acquired and compared to simulation-based SAR maps. The analysis time (acquisition and SAR calculation) was under 6 minutes. |
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Computer-controlled non-metallic phantom platform to simulate head motion with two degrees of freedom |
| Jacob Horne1, Reggie Taylor2, and Tong Xu3 | ||
1Department of Mechanical & Aerospace Engineering, Carleton University, Ottawa, ON, Canada, 2Institute of Mental Health Research, The Royal Ottawa Mental Health Centre, Ottawa, ON, Canada, 3Department of Physics, Carleton University, Ottawa, ON, Canada |
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Keywords: Phantoms, Motion Correction, Dynamic phantom A computer-controlled non-metallic head phantom platform was designed and constructed from 3D-printed parts. Driven by pneumatic stepper motors, the platform can simulate head motion with two degrees of freedom: tilting and rolling, with angular step resolution of 0.0833 degree and 0.227 degree, respectivily. A "neck/spine" design allows different static head phantoms to be mounted to the platform while still be able to fit inside standard head coils. The platform was tested on a PET/MRI scanner and successfully produced motion artifact with simulated motion. |
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What should I use to fill my Ultra-high Field MRI phantom? |
| Felix Horger1,2,3, Jyoti Mangal1,2,3, Raphael Tomi-Tricot1,2,3,4, David Carmichael1,2,3, Joseph Hajnal1,2,3, and Shaihan Malik1,2,3 | ||
1Biomedical Engineering Department, School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom, 2Centre for the Developing Brain, School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom, 3London Collaborative Ultra high field System (LoCUS), London, United Kingdom, 4MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom |
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Keywords: High-Field MRI, Phantoms We explored commonly used substances for phantoms, air, water, oil and Perfluoropolyether, for their suitability for imaging at ultra-high field (7T). We illustrate the impact of susceptibility matching and how to prevent transmit field doming by selecting a substance with low dielectric constant. This work provides insights into the variety and expected magnitude of effects and can serve as guidance when designing a phantom for a specific application. |
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Is the ASTM F2182 Gel Phantom Adequate for Determining Worst-Case RF-Induced Heating of Implanted Medical Devices? |
| Grant Monroe Baker1, Eric David Anttila1, Alan Ross Leewood1, and David Carl Gross1 | ||
1MED Institute, West Lafayette, IN, United States |
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Keywords: Safety, Safety, Heating, RF-Induced Heating, MRI Safety Evaluations, Simulation ASTM F2182 was developed to evaluate RF-induced heating near passive implanted medical devices by subjecting an implant within an average tissue-mimicking (i.e., electrical and thermal properties) phantom to controlled RF exposure. The purpose of this study was to determine if the ASTM F2182 phantom is adequate for determining worst-case RF-induced heating of implanted medical devices. Results from this study display that device temperature rises in the ASTM F2182 are significantly higher than in-vivo temperature rises, regardless of tissue-specific properties and local blood perfusion incorporation to the phantom, indicating that the ASTM gel phantom is adequate for RF-induced heating evaluations. |
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Hydroxyethylcellulose as a tissue mimicking phantom gel: Characterizing the temperature response at 0.5T |
| Diego F Martinez1, Curtis N. Wiens2, Chad T. Harris2, Will B. Handler1, and Blaine A. Chronik1,3 | ||
1The xMR Labs, Physics and Astronomy, Western University, London, ON, Canada, 2Research and Development, Synaptive Medical, Toronto, ON, Canada, 3Medical BioPhysics, Western University, London, ON, Canada |
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Keywords: Phantoms, Thermometry Temperature Mapping at 0.5T offers an accessible method for non-invasively tracking thermal procedures, relying on tissue temperature response of properties such as Proton Resonant Frequency, Apparent Diffusion Coefficient, or T1. To evaluate performance of temperature mapping using these properties, Hydroxyethyl Cellulose – a tissue mimicking gel – was formulated using the ISO 10974:2018 standard and doped with CuSO4 to match representative tissue T1 values. Temperature response of each of these parameters was: PRF parameter α= (-8.74 ± 0.12) x 10-3 ppm/°C, T1 parameter (12.02 ± 0.07) ms/°C, and ADC parameter (5.34 ± 0.063) x 10-5 mm2/s/°C, all in acceptable range. |
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Relaxometry phantoms: Are there alternatives to paramagnetic additives? |
| Victor Fritz1 and Fritz Schick1 | ||
1Section on Experimental Radiology, Department of Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany |
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Keywords: Phantoms, Relaxometry Phantoms used for relaxometry usually consist of a gelling agent doped with paramagnetic salt. However, since the use of paramagnetic additives can be disadvantageous for certain purposes, there is a great interest in finding other suitable substances. In this work, soy-lecithin-agar gels are presented and evaluated as an alternative phantom material for the construction of relaxometry phantoms with tissue-like relaxation times. They were found to work quite well. Soy-lecithin-agar gels are easy to prepare and allow independent adjustment of T1 and T2. Relaxation times of different tissues (muscle, liver, pancreas, kidney) could be successfully mimicked. |
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An open-source platform for simulating internal organ motion: Preliminary results |
| Eddy Solomon1 and Leeor Alon2 | ||
1Radiology, Weill Cornell Medical College, New York, NY, United States, 2Center for Advanced Imaging Innovation and Research, New York University School of Medicine, New York, NY, United States |
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Keywords: Phantoms, Motion Correction Motion-correction techniques require an objective quantitative assessment under controlled conditions. In this work, we present an open-source platform for simulating internal ‘organ’ motion under realistic scan conditions. The phantom was composed of two partitions which include a high-resolution inner compartment translated in space using a Lorentz force, within a larger body-like second compartment. The motion phantom was controlled using custom-made software and was tested with a radial MR sequence, demonstrating motion-resolved capabilities. |
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Development of an MR-Compatible Motion Phantom to Evaluate Motion-Robust Quantitative MRI |
| Jiayi Tang1,2, James Rice2,3, Jack Gwertzman3, Scott B. Reeder1,2,4,5,6, Alejandro Roldán-Alzate2,3, and Diego Hernando1,2 | ||
1Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, 2Radiology, University of Wisconsin-Madison, Madison, WI, United States, 3Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, United States, 4Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States, 5Medicine, University of Wisconsin-Madison, Madison, WI, United States, 6Emergency Medicine, University of Wisconsin-Madison, Madison, WI, United States |
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Keywords: Phantoms, Motion Correction Chemical-shift encoded (CSE) MRI can quantify PDFF and R2* as biomarkers for liver fat and iron deposition, respectively, but conventional methods (3D-CSE) are not motion-robust. Recent methods (2D-CSE-FAM) have been proposed which demonstrate motion-robustness; the evaluation of these methods urges the development of a MR-compatible motion phantom. In this work, we constructed such a phantom, validated it via video tracking, and used it to show motion artifacts and quantification biases in 3D-CSE, identify a potential source of bias in axial R2* 2D-CSE-FAM acquisitions, and confirm the motion-robustness of coronal 2D-CSE-FAM. |
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Colloidal Cell Mimics as Reference System for Diffusion MRI Experiments |
| Henrik zu Jeddeloh1,2, Dominik Ludwig1, Julian Rauch1,2, Frederik Laun3, Mark Ladd1,2,4, Karel Klika5, and Tristan Anselm Kuder1,2 | ||
1Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany, 3Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany, 4Faculty of Medicine, Heidelberg University, Heidelberg, Germany, 5Molecular Structure Analysis, German Cancer Research Center (DKFZ), Heidelberg, Germany |
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Keywords: Phantoms, Diffusion/other diffusion imaging techniques, Cell Mimics, Polymerized Spheres In order to verify modern diffusion MRI sequences, a well-defined reference system consisting of polymerized, hollow microspheres with a hole in the surface is synthesized. This reference system can model the diffusion properties of cells with varying size1,3 and membrane permeability2. To produce these cell mimics3, tripropyleneglycol-monomethylether monomer was mixed with an ammonia solution with polystyrene particles to initiate a nucleation process. The droplets were inflated in an NaOH solution and then hardened under UV exposure. Lastly, the polystyrene particles were dissolved. Scanning Electron Microscope images and DWI measurements were acquired to verify the quality of the cell mimics. |