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| 1085 | Computer 92
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A currentless remote decoupling circuit for receive-only endoscopic MRI coils using negative impedance converters |
| Sina Marhabaie1, Georges Willoquet1, Rose-Marie Dubuisson1, Bruno Quesson2,3,4, and Marie Poirier-Quinot1 | ||
1Université Paris-Saclay, BioMaps, Orsay, France, 2IHU L’Institut de RYthmologie et de Modélisation Cardiaque (LIRYC), Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, 33600 Pessac, Bordeaux, France, 3Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Université de Bordeaux, 33000, Bordeaux, France, 4INSERM, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, Université de Bordeaux, 33000, Bordeaux, France |
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Receive-only coils must be decoupled from the transmit coil during excitation. For conventional coils, decoupling is achieved using a resonant trap, which is switched during B1 transmit. However, in situations with very limited space like intravascular coils, this method remains problematic. We aimed to address efficient remote decoupling of a receive-only coil. We implemented an alternative approach by adding a “negative resistance” to the trap. This negative resistance is tailored in such a way that cancels out the positive resistance of the blocking trap, hence augmenting the quality factor of the trap and thus the decoupling efficiency. |
| 1086 | Computer 93
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New Endo Coil and Novel Methods for Improving mpMR-TRUS Guided Fusion Prostate Biopsies with Hyperpolarized C-13 Pyruvate Molecular Imaging |
| Daniel Tewelde Gebrezgiabbhier1,2, Hsin-Yu Chen3, Robert Bok3, Lucas Carvajal3, Matthew Cooperberg2, Hao Nguyen2, Katsuto Shinohara2, Kimberly Okamoto3, Mary Frost3, Zhen Wang3, Michael Ohliger3, Jeremy Gordon3, Peder Larson3, Rahul Aggarwal2, and Daniel Vigneron3 | ||
1Bioengineering, University of California, San Francisco, CA, United States, 2School of Medicine, University of California, San Francisco, CA, United States, 3Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States |
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A new 13C/1H endorectal coil was designed, 3D printed, and manufactured with optimal dimensions to improve the comfort and tolerability for patients and provide higher SNR over the original endorectal coil used for over a decade. After bench and phantom tests, the new endorectal coil was applied in patient studies for mpMRI-TRUS guided fusion prostate biopsies with hyperpolarized C-13 pyruvate molecular imaging in three patients on active surveillance. The results of this novel approach with the new 13C/1H coil provides an increase in sensitivity, image quality and ultimately supports better detection of lesions. |
| 1087 | Computer 94
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Water-Immersed 8-Dipole Receive Array for MR-Guided Focused Ultrasound of the Brain at 3T |
| Adam Mitchell Maunder1,2, Samuel Pichardo3, G. Bruce Pike3, Melany Mclean3, Fraser Robb4, Ashwin Iyer2, and Nicola De Zanche1,5 | ||
1Oncology, University of Alberta, Edmonton, AB, Canada, 2Electrical and Computer Engineering, University of Alberta, Edmonton, AB, Canada, 3Departments of Radiology and Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, 4GE Healthcare Inc., Aurora, OH, United States, 5Medical Physics, Cross Cancer Institute, Edmonton, AB, Canada |
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The piezoelectric transducer array in magnetic resonance guided focused ultrasound shields the RF body-sized birdcage (BC) fields, leading to regions of low receive sensitivity that hinder MR thermometry and structural imaging. This work presents a flexible, acoustically transparent receive array consisting of dipole sections that mimic loops and are contained within the water bath of the ultrasound transducer array helmet surrounding the head. Adjacent elements are decoupled by shared current paths and lumped inductors. In simulation, the receive sensitivity is increased by 7.8-fold compared to a BC and causes a negligible alteration of the transmit field and specific absorption rate. |
| 1088 | Computer 95
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Robust Fiducial-based Registration for Mechatronics-Assisted MRI-guided Focal Laser Ablation of Localized Prostate Cancer |
| Eric Knull1,2, Claire Park2,3, Jeffrey Bax2, David Tessier2, and Aaron Fenster1,2,3 | ||
1Biomedical Engineering, Western University, London, ON, Canada, 2Robarts Research Institute, London, ON, Canada, 3Medical Biophysics, Western University, London, ON, Canada |
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MRI-guided focal laser ablation (FLA) is a promising minimally-invasive therapy method for men with localized prostate cancer. We previously developed an MR-compatible mechatronic system capable of transperineal needle delivery within an in-bore 3T MRI environment. This work presents an improved multi-fiducial structure for robust registration of the mechatronic system for MRI-guided FLA needle delivery. Real-time MRI-guided needle delivery was performed in a tissue-mimicking prostate phantom to virtual targets simulating focal ablation zones. With the implementation of the improved multi-fiducial structure, mechatronics-assisted MRI-guided needle delivery enables a 1.44 mm ablation radius, showing potential utility for accurate FLA to small prostate lesions. |
| 1089 | Computer 96
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A multi-directional laser ablation device for 3D conformational ablation guided by real-time volumetric MR-thermometry |
| Manon Desclides1,2,3, Guillaume Machinet4, Christophe Pierre4, Valéry Ozenne1,3,5,6, Stéphane Chemouny2, and Bruno Quesson3,5,6 | ||
1UMR5536 CRMSB, Université de Bordeaux, Bordeaux, France, 2Certis Therapeutics, Pessac, France, 3IHU Liryc, Electrophysiology and Heart Modeling Institute, Hopital Xavier Arnozan, Pessac, France, 4ALPhANOV, Talence, France, 5Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, University of Bordeaux, Bordeaux, France, 6INSERM, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France |
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We present here a new laser device allowing us to induce local temperature increase in several directions around the inserted probe to create conformational thermal ablation. The device incorporates 6 independent emitters illuminating several angles radially to the probe. We illustrate the capabilities of the device to create various heating shapes that can be visualized by real-time 2D multi-slice MR-thermometry. |
| 1090 | Computer 97
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16-Channel Hybrid Dipole+Loop RF Applicator for Thermal MR at 7.0 Tesla |
| Nandita Saha1, Andre Kuehne2,3, Thomas Wilhelm Eigentler1,4, and Thoralf Niendorf1,2,5 | ||
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, 2MRI.TOOLS GmbH, Berlin, Germany, 3MT MedTech Engineering GmbH, Berlin, Germany, 4Technische Universität Berlin, Chair of Medical Engineering, Berlin, Germany, 5Experimental 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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This work proposes the concept of a loop and SGBT dipole antenna array for diagnostic proton (1H) imaging and thermal intervention at 7.0T MRI. Dipole antennas are the general choice for RF induced heating application as they can be made to operate over a broadband frequency range, have symmetric B1+ field and provide a central E-field distribution. Adding the inherently orthogonal and thus well-decoupled electromagnetic (EM) fields of loops to the dipoles provides additional degrees of freedom for RF shimming and thermal intervention not afforded by only using dipole antennas. |
| 1091 | Computer 98
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Towards motion robust MRT during Microwave Hyperthermia by integrating an 8-channel receiver coil array into the MRcollar |
| Kemal Sumser1, Gennaro G Bellizzi1, Juan A Hernandez-Tamames2, Gerard C van Rhoon1, and Margarethus M Paulides1,3 | ||
1Department of Radiotherapy, Erasmus Medical Center Rotterdam, Rotterdam, Netherlands, 2Department of Radiology and Nuclear Medicine, Erasmus Medical Center Rotterdam, Rotterdam, Netherlands, 3Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands |
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In the head and neck region, precise heating and temperature monitoring is a challenge. The MRcollar, an MR compatible head and neck microwave hyperthermia applicator has been developed for conformal heating and to enable MR thermometry (MRT) during the treatment. To deliver on the needs of accurate temperature monitoring, the MRcollar has been equipped with 8-channel receiver coil array. This coil array improves increased the SNR by 5 times compared to the body coil of the MRcollar. Increase in the SNR also led to improvement in the MRT precision, from 0.91 °C to 0.37 °C. |
| 1092 | Computer 99
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3D stack-of-stars MR thermometry sequence during hepatic microwave ablation: a phantom study with a commercially available microwave generator |
| Dominik Horstmann1, Bennet Hensen1, Karen Meyer zu Hartlage1, Daniel Luca Reimert1, Josef Joaquin Löning Caballero1, Frank Wacker1, and Marcel Gutberlet1 | ||
1Hannover Medical School, Hannover, Germany |
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A 3D stack-of-stars MR-thermometry sequence was developed and evaluated during hepatic microwave ablation in a chicken phantom. A commercially available microwave generator (MWG) working in pulsed mode controlled by a temperature sensor was used. Results show a spatially dependent phase-offset in the MR-image only during active ablation mode of the pulsed MWG impairing thermometry. Consequently, 73% of thermometry data were discarded for the fixed phantom yielding a temperature precision of 0.72°C±0.60°C whereas 94% were discarded for the moving phantom with an accuracy of 1.08°C±1.25°C. For clinical MR-thermometry, an MWG with less EMI is required to improve resolution and temperature precision. |
| 1093 | Computer 100
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Application of Haralick Texture Analysis to Differentiate Suspicious Prostate Lesions from Normative Tissue on Low-field MRI |
| Dang Bich Thuy Le1, Ram Narayanan1, Meredith Sadinski1, Kathryn Nicholas2, Aleksandar Nacev1, Dinesh Kumar1, and Srirama Venkataraman1 | ||
1Promaxo, Oakland, CA, United States, 2Lakeland Radiologists PA, Jackson, MS, United States |
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Haralick texture features extract frequencies of local spatial variations in signal intensity, quantifying pixel relationships within regions of interest. In this study, Haralick texture features were used to differentiate biopsy-proven, cancerous lesions from non-suspicious regions in low-field MR images. The results demonstrate consistency in texture measures for cancerous regions compared to non-suspicious, where Energy and Homogeneity are elevated while Contrast and Correlation are reduced within cancerous regions compared to non-suspicious regions. |
| 1094 | Computer 101
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Construction of a Tx/Rx body coil on a rotatable patient capsule for MR-guided particle therapy |
| Kilian A. Dietrich1,2,3, Sebastian Klüter2,4,5, Jürgen Debus1,2,3,4,5,6,7,8, Fabian Dinkel9, Gernot Echner9, Mark E. Ladd1,3,8, and Tanja Platt1,2 | ||
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Department of Radiation Oncology, Heidelberg University, Heidelberg, Germany, 3Faculty of Physics, Heidelberg University, Heidelberg, Germany, 4National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany, 5Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany, 6National Center for Tumor Diseases (NCT), Heidelberg, Germany, 7German Cancer Consortium (DKTK), Heidelberg, Germany, 8Faculty of Medicine, Heidelberg University, Heidelberg, Germany, 9German Cancer Research Center (DKFZ), Heidelberg, Germany |
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An RF body coil compatible with particle therapy was built for a clinical MR scanner at 1.5T with a rotatable patient capsule. The attenuation of 1H+ and 12C6+ ions due to inelastic scattering was calculated for different materials to estimate the detrimental effects of the RF coil on the particle beam. The imaging capabilities could be demonstrated with phantom measurements at different flip angles, and corresponding transmit and receive characteristics were analyzed and compared to electromagnetic field simulations for both a horizontal and a tilted position of a phantom. |
| 1095 | Computer 102
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Acoustically-transparent passive RF field repeater elements for the mitigation of the low-signal artifact and improved sensitivity in MRgFUS |
| Isabellle Saniour1, Victor Taracila2, Fraser J.L. Robb2, Rena Fukuda1, Jana Vincent2, Henning U. Voss1, Michael G. Kaplitt3, J. Levi Chazen1, and Simone Angela Winkler 1 | ||
1Department of Radiology, Weill Cornell Medicine, New York, NY, United States, 2GE Healthcare, Aurora, OH, United States, 3Department of Neurological Surgery, Weill Cornell Medicine, New York, NY, United States |
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MRgFUS image quality remains poor and suffers from a low-signal band artifact, preventing efficient image acquisition. We propose to place overlapped acoustically transparent loop elements in “passive mode” between the transducer and the head that act as a transmit field repeater/concentrator. Simulation results not only show mitigation of the low-signal band artifact in the thalamus region, but also demonstrate improvement of the RF transmit signal by a factor of 5 and 2 in the upper brain and the thalamus region, respectively. |
| 1193 | Computer 98
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Feasibility of MRI-guided Interventions at a Large-bore New-generation 0.55T Low-Field MRI System |
| Iman Khodarahmi1, Inge M Brinkmann2, Mary Bruno1, Jerzy Walczyk1, Ryan Brown1, and Jan Fritz1 | ||
1Department of Radiology, New York University School of Medicine, New York, NY, United States, 2Siemens Medical Solutions USA Inc, Malvern, PA, United States |
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New generation low-field MRI systems can be ideal for MRI-guided interventions due to wide bore diameters and lower susceptibility artifacts improving patient access and needle visualization, respectively. We evaluated a set of pulse sequences for their suitability for needle visualization using a new-generation 0.55T system and compared the results with those of a clinical 3T system. Interventional needles can be adequately visualized at 0.55T. Using TSE pulse sequences, needle artifacts display more favorable at 0.55T than 3T. SEMAC and HASTE pulse sequences may not facilitate diagnostic needle visualization at 0.55T but are not needed for clinical MR interventions. |
| 1194 | Computer 99
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Passive Real-Time Needle Tracking and Needle Tip Estimation |
| Andreas Reichert1, Samantha Hickey1, Johannes Fischer1, Michael Vogele2, Simon Reiss1, and Michael Bock1 | ||
1Dept. of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, Freiburg, Germany, 2Interventional Systems GmbH, Kitzbuehel, Austria |
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A real-time sequence is presented with automatic adjustment of the imaging plane parallel to a needle. The sequence utilizes the phase-only cross correlation (POCC) algorithm to detect the orientation of an end-effector and to visualize the planned needle pathway. Additionally, it detects a passive marker at the distal end of the needle to calculate the position of the needle tip for real-time display during needle insertion. The sequence is evaluated in a phantom experiment, and both lateral and longitudinal needle insertion accuracies are determined. |
| 1195 | Computer 100
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A Monte Carlo Analysis of Guidewire Safety Comparing a Body and Local Coil Array |
| felipe godinez1,2, Jeffrey W Hand2, Nuno J Teixeira3, Bart R Steensma4, Joseph V Hajnal2, alexander J E Raaijmakers5, and shaihan malik2 | ||
1Radiology, University of California, Sacramento, CA, United States, 2Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 3Perinatal Imaging, King's College London, London, United Kingdom, 4Center for Image Sciences, University Medical Center Utrecht, Utrecht, Netherlands, 5Biomedical Engineering, Medical Imaging Analysis, Eindhoven University of Technology, Eindhoven, Netherlands |
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Metallic Endovascular devices can be unsafe when used during MR guided procedures. A potential solution to the heating problem might be to use a local coil instead of a body coil to excite the imaging volume. In this work we present a Monte Carlo analysis using many random guidewire trajectories and the transfer function to estimate the scatter electric field at the guidewire tip imbedded in a heterogenous dielectric. |
| 1196 | Computer 101
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Fast 3D Passive Needle Localization for MR-Guided Interventions using Radial White Marker Acquisitions and CNN Postprocessing |
| Jonas F. Faust1,2, Axel J. Krafft2, Daniel Polak2, Ralf Vogel3, Peter Speier2, Nicolas G. R. Behl2, Mark E. Ladd4, and Florian Maier2 | ||
1Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany, 2Siemens Healthcare GmbH, Erlangen, Germany, 3Pattern Recognition Lab, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany, 4Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany |
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Accurate 3D localization of biopsy needles during MR-guided interventions is especially challenging due to time restrictions in real-time workflows. While active tracking methods rely on additional RF-sensitive hardware, rapid passive tracking methods often make use of markers or prior knowledge regarding the needle location. In an ex-vivo study, we investigated a novel passive tracking method using heavily undersampled, radial acquisitions in combination with contrast-optimized White Marker imaging and CNN image postprocessing regarding its potential to speed up passive needle artifact localization without the use of additional hardware or prior knowledge on the needle location. |
| 1197 | Computer 102
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Measurement of magnetic fringe fields from a proton pencil beam scanning nozzle causing MR image ghosting artefacts during in-beam MR imaging |
| Ekaterina Semioshkina1, Bradley M. Oborn2, and Aswin L. Hoffmann1 | ||
1Institute of Radiooncology – OncoRay, Helmholtz-Zentrum Dresden – Rossendorf, Dresden, Germany, 2Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, Australia |
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Proton therapy (PT) is expected to benefit from real-time MRI guidance. However, the integration of MRI and PT is challenging due to the interaction between the magnetic fringe fields of the PT beamline and the B0-field of the MR scanner. In this study, we measured the magnetic fringe field of the PT beamline. The measurement data will be used to validate a finite element model. With a match to this model, we can proceed to investigate what type of magnetic shielding solution would be needed to decouple the magnetic fields of the PT and MRI systems. |
| 1198 | Computer 103
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Phase-Based B1 Mapping in a 65 mT Single-Sided Prostate MRI Scanner |
| William A Grissom1, Meredith Sadinski2, Alek Nacev2, and Muller De Matos Gomes2 | ||
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 2Promaxo, Oakland, CA, United States |
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B1 mapping is important to characterize non-uniform coil geometries and to optimize imaging sequences and image reconstructions in low-field MRI, but is made challenging by point-of-care single-sided imaging geometries with large frequency bandwidths and B1 ranges. We propose a high-bandwidth phase-based B1 mapping technique based on a CHORUS pulse sequence with alternated frequency sweep polarities, which has a wide (40 kHz) imaging bandwidth and high B1 dynamic range. The sequence was implemented and validated on a 65 mT single-sided prostate MRI scanner in phantom scans with butterfly coil transmit and local multichannel receive. |
| 1199 | Computer 104
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Type-III NUFFT Image Reconstruction for a 65 mT Single-Sided Prostate MRI Scanner with Non-Linear Gradient Fields |
| Meredith Sadinski1, Ram Narayanan1, Alek Nacev1, and William A Grissom2 | ||
1Promaxo, Oakland, CA, United States, 2Biomedical Engineering, Vanderbilt University, Nashville, TN, United States |
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Single-sided low-field MRI scanners can provide image guidance during interventions such as prostate biopsies without restricting surgical access. However, image reconstruction from these scanners is challenging due to the non-linearity of their gradient fields and inhomogeneous B0 fields. At the same time, non-Cartesian sampling is desirable for these scanners to maximize SNR efficiency and provide self-navigation. In this work, we report a fast iterative 3D Type-III NUFFT reconstruction for a 65 mT single-sided prostate imager, with non-linear single-sided gradient fields and a built-in B0 gradient field. The reconstruction was compared with a model-based reconstruction for a high-bandwidth radial RARE acquisition. |
| 1200 | Computer 105
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Simulating the effects of off-resonance effects from a CHORUS pulse sequence in a single sided, low-field MRI system. |
| Kartiga Selvaganesan1, Muller Gomes2, Will Grissom3, and Alek Nacev2 | ||
1Yale School of Engineering & Applied Science, Yale, New Haven, CT, United States, 2Promaxo, Oakland, CA, United States, 3Biomedical Engineering, Vanderbilt University, Nashville, TN, United States |
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Moving towards single-sided, low-field MRI systems can increase the portability and access to this invaluable clinical tool. However, the B0-fields generated by these systems are highly inhomogeneous, and severe artifacts arise when the RF pulse does not cover the full bandwidth of spin resonances. In this study, we have developed a simulation algorithm that will allow us to better simulate the phase variations induced by B1 and B0 inhomogeneities and help us design RF schemes to remove unwanted phase to produce higher quality images. |
| 1201 | Computer 106
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Continuous Perfusion Measurement With Singled Sided Low Field MR |
| Alice Little1,2, Dion Thomas2, Shieak Tzeng3, and Sergei Obruchkov2 | ||
1The University of Auckland, Auckland, New Zealand, 2Victoria University of Wellington, Wellington, New Zealand, 3University of Otago, Wellington, New Zealand |
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In this study we focus on exploring the use of a single sided low-field MR systems to continuously measure perfusion. For this purpose we developed a contrast-free measurement technique - tentatively named Inhomogeneous Flow-sensitive Alternating Inversion Recovery (IFAIR). This new technique, adapted from the FAIR ASL protocol, was designed to be suitable for inhomogeneous field conditions and to function without pulsed gradient fields. The IFAIR signal response displayed a consistent proportional relationship to flow velocity, with potential to allow for quantitative flow-dependent measurements. |
| 1202 | Computer 107
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A new single channel method for electromagnetic interference reduction on a 50 mT permanent magnet system |
| Javad Parsa1,2, Thomas O'Reilly2, and Andrew Webb2 | ||
1Percuros B.V., Leiden, Netherlands, 2Leiden University Medical Center, Leiden, Netherlands |
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External electromagnetic interference (EMI) in unshielded low field and portable MRI systems can swamp the signal, and various multi-detector methods have been developed to minimize it. A new EMI cancellation method designed for a single-channel receiver-system has been implemented on a 50 mT system by using the MR-inactive channel of a birdcage coil and a 180o power hybrid. This method results in up to a 97% reduction in the standard deviation of external EMI. |
| 1203 | Computer 108
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Development of a Low-Cost B0 Field Mapping Device |
| Marcel Eisenmann1,2, Ivan Fomin1,2, Marcus Prier1,3, Georg Rose1,2, and Oliver Speck1,3 | ||
1Research Campus STIMULATE, Otto von Guericke University, Magdeburg, Germany, 2Institute for Medical Engineering, Otto von Guericke University, Magdeburg, Germany, 3Department for Biomedical Magnetic Resonance, Otto von Guericke University, Magdeburg, Germany |
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Field mapping devices are used to determine the spatial distribution of magnetic fields. As magnetic devices are very unique in shape and size, commercially available mapping devices are often complex and customised and therefore too costly for small-format magnetic resonance imaging (MRI) systems and the open-source community. A low-cost field mapping device with a Hall sensor for the OCRA tabletop MRI system1 is developed. Field maps are measured and compared against a commercial Hall probe. The presented measurements show that the developed device can compete with commercially available devices. |
| 1204 | Computer 109
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Characterising the Magnetic Field Inhomogeneity for Open MRI at 0.5T using a Screened Coil NMR Probe Design |
| Dipendra Jayantilal Mistry1, Penny Gowland1, Olivier Mougin1, Richard Bowtell1, and Paul Glover1 | ||
1Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom |
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Image distortion caused by field inhomogeneity and instability is a major limitation for open MRI systems. Magnetic Field Monitoring (MFM) is a well-documented approach to characterise and thus compensate for these effects using an array of NMR probes. Here a novel NMR probe with a secondary coil is presented, which is designed to protect the pre-amplifier during transmission of a uniform B1 field. Preliminary data has verified this result and temporal variations of the B0 field have been observed. This approach will be developed with multiple probes to measure and compensate for the spatio-temporal response of the system. |
| 1287 | Computer 83
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The HYPMED PET/MRI Insert for Breast Cancer |
| Yannick Kuhl1, Stephan Naunheim1, Bjoern Weissler1,2, Vanessa Nadig1, David Schug1,2, Florian Mueller1, Harald Radermacher1, Pierre Gebhardt1, Nicolas Gross-Weege1, Teresa Nolte1, Martino Borgo3, Marcel de Koning3, Menno Mathlener3, Jeroen Koeleman3, Frank van Duin3, Arold Dekker3, Wout Schut3, Jos van den Berghe3, Daniel Gareis4, Turgay Celik4, André Salomon5, Dennis Schaart6, Dimitri Kuznetsov6, René Bakker6, Karl-Josef Langen7, Christiane Kuhl8, and Volkmar Schulz1,2,9,10 | ||
1Physics of Molecular Imaging Systems (PMI), Experimental Molecular Imaging (ExMI), Aachen, Germany, 2Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany, 3Futura Composites B.V., Heerhugowaard, Netherlands, 4NORAS MRI Products GmbH, Hoechberg, Germany, 5Philips Research, Eindhoven, Netherlands, 6Delft University of Technology, Delft, Netherlands, 7Forschungszentrum Juelich, Juelich, Germany, 8Department of Diagnostic and Interventional Radiology, University Hospital Aachen, Aachen, Germany, 9Physics Institute III B, RWTH Aachen University, Aachen, Germany, 10Fraunhofer Institute for Digital Medicine MEVIS, Aachen, Germany |
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Within the H2020 EU project HYPMED, we have developed a PET insert that can be moved into a 1.5 T MRI Philips Ingenia turning this into a simultaneous MRI-PET device for breast cancer applications. The PET insert consists of two independent PET rings with a field of view of 28$$$\times$$$10 cm² and two dual-channel local receive coils. Each ring consists of 14$$$\times$$$2 detector blocks of which each features a three-layer LYSO crystal array with 1.3 mm pitch. We will present the first PET and MRI results of our system. |
| 1288 | Computer 84
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Feasibility study of novel 8-channel stacked 1H/31P transceiver coil as PET insert for 7T MRI |
| Ria Forner1, Woutjan Branderhorst1, Debra Rivera2, Alexander Raaijmakers1,2, Dimitri Welting1, and Dennis Klomp1 | ||
1UMC Utrecht, Utrecht, Netherlands, 2Eindhoven University of Technology, Eindhoven, Netherlands |
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The feasibility of simultaneous 1H/31P PET/MR imaging added-on to an existing 7T MRI system was assessed. Space constraints preclude using whole-body birdcages. Instead, an 8-channel 1H dipole array stacked with additional 8-31P channels is set up. By positioning PET detectors between the RF-shield and gradient coil, further shielding of the PET-crystals and electronics can be omitted. 8-channel 31P scans had a higher SNR compared to a birdcage setup. The 1H/31P setup gives ~5% degradation of PET sensitivity. Similarly, the impact of the new setup (proximity of the RF shield) was insignificant for MRI performance at both frequencies. |
| 1289 | Computer 85
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A Novel PET Optimized Head Neck Coil for 3T Simultaneous MRPET System |
| Yun-Jeong Stickle1, Mark Giancola1, Clyve Konrad Follante1, Thomas Stickle1, Fraser Robb1, Holly Blahnik2, and Tae-Young Yang1 | ||
1GE Healthcare, Aurora, OH, United States, 2GE Healthcare, Waukesha, WI, United States |
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A PET optimized 21- Element Head Neck coil is described for acquiring high-sensitivity MR (Magnetic Resonance) images and good quality PET images of head/neck, carotids, and cervical spine at 3 Tesla simultaneous MR/PET system. This Head Neck prototype2 coil has been optimized to minimize the interference with -ray detection of the PET without sacrificing MR image quality. In this study, we developed a foam technology to replace the rigid plastic coil formers, optimized arrangement of components (internal cables, internal cable baluns, feed boards and decoupling boards) and introduced new mechanical fastener and snap features. |
| 1290 | Computer 86
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MRI compatibility for a novel simultaneous PET/MRI system with scintillator-based RF shielding for preclinical 7 T MRI scanner |
| Laiyin Yin1, Nicolas Gross-Weege1, Teresa Nolte1, Bjoern Weissler1,2, David Schug1,2, and Volkmar Schulz1,2,3,4 | ||
1Department of Physics of Molecular Imaging Systems, Institute of Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany, 2Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany, 3Physics Institute III B, RWTH Aachen University, Aachen, Germany, 4Fraunhofer Institute for Digital Medicine MEVIS, Aachen, Germany |
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We present a preclinical PET/MRI system with highly-integrated PET modules in which the RF shielding is implemented on scintillator level for a 7 T Bruker BioSpec 70/20. The PET system's RF housing size is minimized by excluding parts of the scintillator while maintaining the RF shielding properties through the scintillator-integrated shielding. The modules are mounted inside the MRI coil, between resonator and RF screen. MRI compatibility is evaluated in a mouse phantom by means of spurious noise scans and SNR evaluations of standard morphologic sequences, while the PET system is off, idle and measuring. Additionally, postmortem mouse images are presented. |
| 1291 | Computer 87
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MRI tractography-guided PET image reconstruction regularisation using connectome-based nonlocal means filtering |
| Zhuopin Sun1, Georgios Angelis1,2, Steve Meikle3,4, and Fernando Calamante1,4,5 | ||
1School of Biomedical Engineering, The University of Sydney, Sydney, Australia, 2Australian National Imaging Facility, The University of Sydney, Sydney, Australia, 3Faculty of Medicine and Health, The University of Sydney, Sydney, Australia, 4Brain and Mind Centre, The University of Sydney, Sydney, Australia, 5Sydney Imaging, The University of Sydney, Sydney, Australia |
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Diffusion MRI (dMRI) can provide a wealth of information about brain microstructure and connectivity, but its use in PET-MRI image reconstruction has not been exploited. We incorporated dMRI-derived prior information as a regulariser into the iterative PET One-Step Late Maximum A Posteriori (OSLMAP) reconstruction algorithm. The proposed regularisation method has unique advantages of providing more informative and targeted denoising and regularisation based on the complementary structural connectivity information from dMRI. |
| 1292 | Computer 88
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An Evaluation of the Diagnostic Quality of Machine Learning Approaches for PET Attenuation Correction in Neuroimaging: A Meta-Analysis |
| Confidence Raymond1,2, Jurkiewicz Michael 1,2, Akin Orunmuyi3, Dada Oluwaseun Michael 4, Claes Nøhr Ladefoged5, Jarmo Teuho6, and Udunna Anazodo1,2 | ||
1Medical Biophysics, Western University Ontario, London, ON, Canada, 2Lawson Health Research Institute, LONDON, ON, Canada, 3Anaesthesia, College of Medicine, Ibadan, Nigeria, 4Physics, Federal University of Technology, Minna, Nigeria, 5Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Denmark, 6Turku PET Centre, Turku University, Turku, Finland |
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The last decade has seen an increase in the application of machine learning (ML) methods to PET/MRI attenuation correction (AC). This systematic review provides a head-to-head comparison between state-of-the-art ML methods and clinical standards for AC to determine the clinical feasibility of ML approaches PET AC. We extracted numerical values for image quality, tissue classification, regional and global diagnostic performance. The pooled mean relative error for global performance was 0.87 ± 1.3%, the quality of evidence for all outcomes ranged from moderate to very low. Our findings suggest that ML-AC performance is within acceptable limits for clinical PET/MR neuroimaging. |
| 1293 | Computer 89
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Non-rigid Motion-compensated Whole-heart 18F-FDG PET and 3D T2 mapping in a hybrid PET-MR system |
| Alina Schneider1, Camila Munoz1, Alina Hua1, Sam Ellis1, Sami Jeljeli2, Karl P Kunze1,3, Radhouene Neji1,3, Eliana Reyes1, Tevfik F Ismail1, René M Botnar1, and Claudia Prieto1 | ||
1School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 2PET Centre, St Thomas’ Hospital, King’s College London & Guys and St Thomas’ NHS Foundation Trust, London, United Kingdom, 3MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom |
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Simultaneously acquired 18F-FDG PET-MR imaging and quantitative 2D T2-mapping have been suggested for improved diagnostic accuracy of cardiac sarcoidosis, however misregistration between imaging modalities makes clinical interpretation challenging. Here we used a recently proposed free-breathing motion-corrected 3D whole-heart T2-mapping sequence acquired simultaneously with 18F-FDG PET at a 3T PET-MR system. This approach enables the non-rigid motion-correction for both the 3D T2-mapping and the PET data to the same respiratory position, resulting in aligned volumes for improved clinical interpretation. In this study, we tested this approach in a patient with suspected cardiac sarcoidosis. |
| 1294 | Computer 90
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Multiparametric MRI, sodium MRI, and PSMA PET of prostate cancer with histological validation of Gleason grade |
| Josephine Tan1, Alireza Akbari1, Matthew Fox2, Mena Gaed3, Madeleine Moussa4, Jose A Gomez4, Zahra Kassam5, William Pavlosky5, Joseph L Chin6, Stephen Pautler6, Nicholas Power6, Aaron D Ward1,2, Glenn S Bauman1,2, Jonathan D Thiessen1,2,5, and Timothy J Scholl1,3,7 | ||
1Medical Biophysics, University of Western Ontario, London, ON, Canada, 2Lawson Health Research Institute, London, ON, Canada, 3Robarts Research Institute, University of Western Ontario, London, ON, Canada, 4Pathology and Laboratory Medicine, University of Western Ontario, London, ON, Canada, 5Medical Imaging, University of Western Ontario, London, ON, Canada, 6Surgery, Division of Urology, University of Western Ontario, London, ON, Canada, 7Ontario Institute for Cancer Research, Toronto, ON, Canada |
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This abstract focuses on the development of an imaging assay based on multiparametric MRI and sodium (23Na) MRI to discriminate between low- and high-grade prostate cancer (PCa) lesions, using Gleason grade defined by whole-mount histopathology as the gold standard and PET targeting the prostate-specific membrane antigen (PSMA) as a validation. Data from the first patient (Gleason score 7) demonstrates that PSMA-PET may be superior in detecting PCa lesions in the transition zone and distant metastases while the sensitivity of the current 23Na radiofrequency system in this study is limited to lesions in the peripheral zone of the prostate. |
| 1367 | Computer 73
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Short-TE diffusion-MRI by combining strong gradients with ultrasonic readout |
| Aris van Ieperen1,2, Chantal Tax1,3, Dennis Klomp1, Bas Vermulst2, Jeroen Siero1,4, Joost van Straalen5, Martijn Heintges5, and Edwin Versteeg1 | ||
1Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2Electromechanics & Power Electronics, Eindhoven University of Technology, Eindhoven, Netherlands, 3CUBRIC, School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom, 4Spinoza Centre for Neuroimaging, Amsterdam, Netherlands, 5Prodrive Technologies B.V., Son, Netherlands |
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For high-resolution diffusion-MRI, strong gradients combined with fast readout are desired. In this study, we propose a gradient system architecture for such strong gradients and fast readouts without nerve stimulation by implementing a filter topology that allows for both low and high frequency gradient waveforms. Two gradient inserts with different specifications are realized and two proposed modulation strategies are implemented in the amplifier firmware. Field measurements demonstrated the desired dual-mode capability of the system. With one gradient insert, a gradient amplitude of 300 mT/m and slew rates well above 10.000 T/m/s can be reached with only 500A&330V as amplifier output. |
| 1368 | Computer 74
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Z-Gradient Array Coil Equipped with a Tunable Shield Array for Creating Multiple-Imaging Volumes |
| Manouchehr Takrimi1 and Ergin Atalar2 | ||
1National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey, 2Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey |
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A z-gradient array coil equipped with a tunable shield array is proposed to achieve multiple imaging volumes that can be shifted along the coil axis. This is achieved by a set of independently tunable power amplifiers that feed the array elements. The proposed array dynamically provides a proper shield for the main array in which its magnetic profile can be adjusted on the fly. Five multiple-region magnetic profiles are simulated to demonstrate the flexibility of the proposed array: (a) a double-gradient profile; (b) shifted version of (a); (c) highly linear double-gradient profile without shielding; (d) triple-gradient profile; (e) quintuple-gradient profile. |
| 1369 | Computer 75
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Design Analysis and Prototype Construction of PNS Optimized MRI Gradient Coils |
| Mathias Davids1,2,3, Livia Vendramini1, Natalie Ferris4,5, Valerie Klein1,3, Bastien Guerin1,2, and Lawrence L. Wald1,2,5 | ||
1Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany, 4Harvard Graduate Program in Biophysics, Harvard University, Cambridge, MA, United States, 5Harvard-MIT Division of Health Sciences and Technology, Boston, MA, United States |
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We describe the process of designing and analyzing two body gradient coils with and without PNS optimization suitable for prototype construction and experimental validation. The optimized coil achieves a 51% increase in PNS thresholds at a 15% inductance penalty. Both coils are construction-ready (single continuous wire path) and have realistic and matched design characteristics (actively shielded, torque/force balanced, high field linearity in 40 cm ROL). We are in the process of constructing coil prototypes, with the ultimate goal of experimentally validating their PNS differences. |
| 1370 | Computer 76
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Diffusion Imaging comparison of high-performance Gradient system (MAGNUS) with clinical MR system. |
| H. Douglas Morris1, Nastaren Abad2, Radhika Madhavan3, Chitresh Bhushan2, Ante Zhu2, Luca Marinelli2, Eric Fiveland2, J Kevin DeMarco4,5, Robert S Shih4,5, Maureen Hood4,5, Gail Kohls4, Kimbra Kenny4, Tom K F Foo2, and Vincent B Ho4,5 | ||
1Radiology and Radiological Sciences, Uniform Services University of the Health Sciences, Bethesda, MD, United States, 2GE Global Research, Niskayuna, NY, United States, 3GE Healthcare, Niskayuna, NY, United States, 4Walter Reed National Military Medical Center, Bethesda, MD, United States, 5Uniform Services University of the Health Sciences, Bethesda, MD, United States |
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Comparisons of the multi-shell DWI is described for the USU/GE MAGNUS 3T head-only gradient system and a clinical whole-body GE MR750 3T magnet system. The advantages of high-performance gradients are shown in analysis outcomes of dMRI metrics. Direct comparison is made between identical diffusion pulse sequences and system optimized sequences for each platform. The shorter TE and high-gradient strength of MAGNUS enhance SNR and diffusion imaging response. |
| 1371 | Computer 77
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Vibration measurements of the SC72 gradient versus field strength in the Iseult magnet |
| Nicolas Boulant1, Cécile Lerman1, Lionel Quettier2, Olivier Dubois2, Frédéric Molinié2, Peter Dietz3, and Guy Aubert2 | ||
1University Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif sur Yvette, France, 2University Paris-Saclay, CEA, Irfu, Gif sur Yvette, France, 3Siemens Healthcare GmbH, Erlangen, Germany |
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The whole-body Iseult 11.7T CEA magnet has delivered its first images after nearly 20 years of research and development. Before reaching this long-waited step, a gradient coil–magnet interaction test campaign was run for several months at 3T, 7T, 10.2T and 11.7T on the same identical system. It included acoustics, vibrations, magnet safety system voltage and power deposition in the He bath measurements. Some vibration results versus field strength are presented here. Vibration amplitudes are shown to increase less than with B0 field strength. |
| 1372 | Computer 78
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Reducing MRI acoustic noise burden with Predictive Noise Cancelling |
| Paulina Šiurytė1, Joao Tourais1, and Sebastian Weingärtner1 | ||
1Imaging Physics, TU Delft, Delft, Netherlands |
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Acoustic noise in MRI is a main source of patient anxiety, with noise levels reaching up to 130 dB. In this work, a low-cost solution is proposed, combining active noise cancelling and direct sequence noise prediction from the scanner gradient inputs. The prediction is based on the linearity between gradient coil input derivative and corresponding acoustic noise. A proposed Predictive Noise Cancelling demonstrated an in-bore noise reduction up to 10 dB despite the system imperfections. |
| 1373 | Computer 79
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Hybrid Superconducting-Permanent Magnet Designs for Short Mid-Field MRI Magnets |
| Alex C Barksdale1,2, Clarissa Cooley1, and Lawrence Wald1 | ||
1MGH, Charlestown, MA, United States, 2MIT, Cambridge, MA, United States |
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Mid-field (0.5T) MRI is an attractive alternative to higher field strengths for improved cost, accessibility and patient comfort. Magnet length is a major determinant of patient comfort/acceptance but is constrained by escalating wire costs. We present a mid-field magnet design using rare-earth permanent magnets to supplement solenoidal superconducting windings, enabling shorter bore lengths than superconducting windings alone. The optimization problem is formulated and solved using linear programming. For a given superconducting wire length, we demonstrate that adding rare-earth materials can reduce bore lengths by 10% using <250kg of rare-earth material for a 5ppm, 0.5T B0 specification over a 450mm DSV. |
| 1374 | Computer 80
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A Fast Magnetostaic Inverse Approach for Subject-Specific ∆B0 Shim Coil Calibration |
| Nicolas Arango1, Jacob White1, and Elfar Adalsteinsson1,2 | ||
1Department of Electrical 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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For a rigidly positioned ∆B0 shim coil, calibration is a one-time process of acquiring high resolution ∆B0 fields. For subject-specific shim coil position, this approach is too slow. We propose a fast magnetostatic inverse approach for subject-specific calibration by only acquiring few, low resolution fieldmaps each with several active shim coils. Our simulation study, which included a noise model and a measured ∆B 0 test case, suggests a scan-time reduction of afactor of 170, reducing calibration time from over an hour to less than a minute with negligible impact on shim quality. |
| 1375 | Computer 81
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Portable magnetic resonance based monitoring of MCA occlusion in an ovine sheep stroke model. |
| Dion Thomas1, Freya Harrison2, Alice Little1,3, Alex King1, Annabel Jain Sorby-Adams4, Shieak Tzeng2, Renee Turner4, and Sergei Obruchkov1 | ||
1Victoria University of Wellington, Wellington, New Zealand, 2University of Otago, Wellington, New Zealand, 3The University of Auckland, Auckland, New Zealand, 4The University of Adelaide, Adelaide, Australia |
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A custom built single sided magnetic resonance system, generates an external region of homogeneous B0 = 0.2T field, a sweet spot, from which signal can be detected. The device is capable of relaxometry, diffusion and perfusion measurements and was used to continuously monitor progress of an MCA occlusion in a ovine sheep stroke model. The data from the device was compared to image data acquired on a clinical 3T MRI system. |
| 1376 | Computer 82
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Improving image quality and acoustic transparency in MRgFUS at 3T using a low-profile, flexible receive coil array |
| Isabellle Saniour1, Fraser J.L. Robb2, Victor Taracila2, James Shin1, Vishwas Mishra1, Rena Fukuda1, Jana Vincent2, Henning U. Voss1, Michael G. Kaplitt3, J. Levi Chazen1, and Simone Angela Winkler 1 | ||
1Department of Radiology, Weill Cornell Medicine, New York, NY, United States, 2GE Healthcare, Aurora, OH, United States, 3Department of Neurological Surgery, Weill Cornell Medicine, New York, NY, United States |
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Transcranial MRgFUS has been successfully used to treat a variety of neurodegenerative diseases. However, body coil brain image quality is poor, and a low-signal band artifact may occur in some regions due to RF wave reflections. Further, acoustic coil transparency has not been addressed extensively to date. In this work, we simulate a 10-channel coil design that can significantly increase the SNR by a factor of 20 over the body coil and thus indirectly improve the signal at the region of interests. Acoustic simulations/experiments exhibit transparency of the FUS-Flex coil as high as 97% at 650 kHz. |
| 1444 | Computer 68
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Folded-End Dipole Transceiver Array for Human Whole Brain Imaging at 7 T. |
| Nikolai I. Avdievich1, Georgiy Solomakha2, Loreen Ruhm1, Anton V Nikulin1,3, Arthur Magill4, and Klaus Scheffler1,3 | ||
1High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2Physics and Engineering, ITMO University, St. Petersburg, Russian Federation, 3Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany, 4Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany |
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In spite of great benefits of 7T MRI, its further clinical development is associated with difficulties in designing RF coils. Recently, we developed a novel type of dipole antennas, a folded-end dipole. In this work we evaluated an 8-element transceiver folded-end dipole array for 7T human head imaging. The array provided ~20% higher Tx-efficiency and significantly better whole-brain coverage than that of a widely-used commercial array. In addition, we evaluated passive dipoles for decoupling the proposed array. In contrast to the common unfolded dipole array, the passive dipoles produce practically no destructive interference with the RF field of the array. |
| 1445 | Computer 69
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A novel 1H-dipole/31P-birdcage transceiver coil for head imaging at 7T |
| Ria Forner1, Ingmar Voogt2, Bart Steensma3, Kyungmin Nam3, Mark Gosselink3, Debra Rivera4, William T Clarke5,6, Aidin Alihaghnejad2, Arjan Hendriks3, and Dennis Klomp1 | ||
1UMC Utrecht, Utrecht, Netherlands, 2Wavetronica B.V., Utrecht, Netherlands, 3University Medical Center Utrecht, Utrecht, Netherlands, 4Eindhoven University of Technology, Eindhoven, Netherlands, 5Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield, United Kingdom, 6Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom |
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A novel coil design with a 31P birdcage and a 1H dipole array is presented for the purpose of fMRS applications. This design allows for free line-of-sight for fMRI and fMRS visual stimulation via mirrors and despite a lower fill-factor performs comparably to a smaller dual-tuned birdcage. The matching of both frequencies is adequate for a range of human head circumferences from 52cm through 57cm. The 31P birdcage performance is not significantly degraded by presence of 1H dipoles when compared to a conventional birdcage dual-tuning strategy with Foster networks. |
| 1446 | Computer 70
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Negligible loss in double tuning when stacking 1H to 31P dipoles in an 8-channel dipole array with 24 receivers at 7T |
| Jabrane Karkouri*1, Ria Forner*2, Martijn Lunenburg3, Ettore Flavio Meliadò3, Catalina Arteaga3, Alexander Raaijmakers4,5, Christopher T. Rodgers†1, and Dennis Klomp†4 | ||
1University of Cambridge, Cambridge, United Kingdom, 2Radiology, UMC Utrecht, Utrecht, Netherlands, 3Tesla Dynamic Coils, Zaltbommel, Netherlands, 4UMC Utrecht, Utrecht, Netherlands, 5Biomedical engineering, Eindhoven University of Technology, Utrecht, Netherlands |
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We present a novel dual dipole coil concept for 7T 31P metabolic imaging in the body. We constructed an array of 8x stacked 1H/ 31P dipoles, evaluating their performance by bench measurements, EM modelling, phantom experiments and in vivo scans in human liver. Parameters such as coupling, transmission efficiency and SAR are compared to those of a whole-body 31P birdcage coil. |
| 1447 | Computer 71
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An 8-channel transmit 64-channel receive compact head coil for Next Gen 7T scanner with head gradient insert |
| Shajan Gunamony1,2 and David Feinberg3 | ||
1Imaging Centre of Excellence, University of Glasgow, Glasgow, United Kingdom, 2MR CoilTech Limited, Glasgow, United Kingdom, 3Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States |
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The NextGen 7T scanner is equipped with a high-performance head gradient insert and hence the radial space available on the patient table for radiofrequency (RF) coils is limited. In addition to a large visual field to support fMRI studies, a split-top receive array on a sliding mechanism is desirable for improved patient comfort. We have developed a novel 8-channel transmit 64-channel receive 7T head coil and implemented a sliding mechanism to operate within the limited space in the head gradient insert. In this abstract, we present the overall coil design, transmit array performance and preliminary phantom results. |
| 1448 | Computer 72
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Performance characterization of three coils for whole brain and/or cervical spinal cord MRI at 7T |
| D Rangaprakash1, Bastien Guerin1, Jason P Stockmann1, Markus W May2, Nibardo Lopez Rios3, Kyle M Gilbert4, Yulin Chang5, Lawrence L Wald1,6, Julien Cohen-Adad3,7,8, Boris Keil1,2, and Robert L Barry1,6 | ||
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, 2Institute of Medical Physics and Radiation Protection, University of Applied Sciences Mittelhessen, Giessen, Germany, 3NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada, 4Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada, 5Siemens Medical Solutions USA Inc., Malvern, PA, United States, 6Harvard-Massachusetts Institute of Technology Division of Health Sciences & Technology, Cambridge, MA, United States, 7Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montreal, QC, Canada, 8Mila – Quebec AI Institute, Montreal, QC, Canada |
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Several neurological diseases affect both the brain and spinal cord. 7T MRI enables better imaging of the narrow cord as well as single-subject prediction using fMRI. However, concurrent brain-cord 7T imaging requires a coil with good SNR and acceleration capabilities in both head and neck, which has been unavailable. To overcome this, we performed flip-angle, SNR, g-factor and tSNR characterization of a custom-built 16Tx/64Rx head/neck radiofrequency coil. We also compared it against a custom-built 8Tx/20Rx cervical spine coil as well as a commercial 8Tx/32Rx brain coil. This hardware will pave the way for concurrent brain-cord 7T MRI in the future. |
| 1449 | Computer 73
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Shielded-coaxial-cable (SCC) coils - the array configuration for maximized central SNR at 7T MRI |
| Sadri Guler1,2, Giovanni Costa3, Vincent Boer2, Maarten Paulides3, Peter Baltus3, Esben Petersen1,2, and Irena Zivkovic3 | ||
1Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Copenhagen, Denmark, 2Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark, 3Electrical Engineering Department, Technical University of Eindhoven, Eindhoven, Netherlands |
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The shielded-coaxial-cable (SCC) coils have been proposed recently as highly decoupled elements per se. The SCC coils are not very sensitive to bending, elongation and various degrees of overlapping. We experimentally investigated the central SNR when the SCC coils are placed in three different arrangements on a cylindrical object. The highest central SNR (more than 30% higher than in the other two arrangements) was obtained when the coils were elongated and adjacent to each other. This arrangement is important when the ROI is located deep inside the field of view, such in c-spine spinal cord or deep brain imaging. |
| 1450 | Computer 74
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SNR Evaluation with High Input Impedance Preamplifier Decoupling Performance for a 2-Layer and 32-Channel Receive Array for Brain Imaging at 7T |
| Paul-François Gapais1,2, Saadou Almokdad2, Michel Luong3, Eric Giacomini2, Elodie Georget1, and Alexis Amadon2 | ||
1Multiwave Imaging SAS, Marseille, France, 2Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, 3CEA, IRFU, Université Paris-Saclay, Gif-sur-Yvette, France |
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With the increasing number of elements in receive arrays, the need to accurately predict coil performance is crucial. Decoupling is usually performed with low-input impedance preamplifier decoupling. Recently, new schematics have been proposed that rely on high-input impedance preamplifiers. A simulation method is proposed here to evaluate preamplifier decoupling performance in this context on a 2-layer array at 7T. Results show a strong influence on the thermal SNR according to the impedance presented by the preamplifier to the coil output. The higher this impedance the higher the SNR, but practical implementation need a trade-off between high impedance and noise-matching. |
| 1535 | Computer 85
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SNR and Field Strength with Small Surface Coils |
| Rolf Pohmann1, Nikolai Avdievitch1, and Klaus Scheffler1,2 | ||
1Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany |
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The increase in SNR with higher field strength is one of the main drivers for ultra high field MRI. Here, the sensitivity gain is determined for phantoms in five different fields between 3 T and 14.1 T, using identical small surface coils and correcting for all scanner specific influences. A strong, more than quadratic SNR gain with increasing field strength was found, which applies to many animal studies and to measurements with weakly loading samples. |
| 1536 | Computer 86
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Human brain POCE MRS at 7T using a 13C birdcage coil and 8 transmit-receive 1H antennas with a 32-channel 1H receive array |
| Sarah M Jacobs1, Jeanine J Prompers1, Wybe JM van der Kemp1, Tijl A van der Velden1, Mark WJM Gosselink1, Ettore F Meliadò1, Hans M Hoogduin1, Graeme F Mason2, Robin A de Graaf2,3, Anja G van der Kolk1,4, Cezar Alborahal1, Dennis W Klomp1, and Evita C Wiegers1 | ||
1Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, Netherlands, 2Department of Radiology and Biomedical Imaging, Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, CT, United States, 3Department of Biomedical Engineering, Yale University School of Medicine, New Haven, CT, United States, 4Department of Radiology, Radboud University Medical Center, Nijmegen, Netherlands |
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We have shown that it is feasible to perform POCE MRS in the human brain at 7T during a uniformly labeled [U-13C] glucose infusion in three healthy volunteers, using a 13C birdcage head coil combined with 8 transmit-receive 1H antennas with a 32-channel 1H receive array. STEAM-POCE and sLASER-POCE provided similar sensitivity for the [4-13C]-Glx-H4 signals. POCE examinations could be performed in two locations, i.e. the frontal and occipital lobe, in one session, allowing them to be easily merged with 1H MRI. |
| 1537 | Computer 87
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On the Noise Correlation in Receive Phased Arrays |
| Paul-François Gapais1,2, Michel Luong3, Saadou Almokdad2, Elodie Georget1, and Alexis Amadon2 | ||
1Multiwave Imaging SAS, Marseille, France, 2Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, 3Université Paris-Saclay, CEA, IRFU, DACM, Gif-sur-Yvette, France |
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The noise covariance matrix is useful for SNR and g-map computation and, with the noise correlation matrix, commonly taken as metrics to characterize decoupling of denser and denser receive arrays. Roemer provided a resistance matrix accounting for noise correlation. In the literature, Bosma defined the noise covariance matrix from the scattering matrix, easing predictions based on electromagnetic simulations or VNA measurements. Here noise correlation is analyzed for 50 Ω power-matched and low-input impedance preamplifiers. As predicted by Bosma, strong coupling does not necessarily imply a high noise correlation, which also depends on the ports impedance matching. |
| 1538 | Computer 88
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Investigation of correlation between surface current and coupling using conventional coils and shielded coaxial cable coils operating at 7T |
| Giovanni Costa1, Sadri Güler2,3, Peter Baltus1, Maarten Paulides1, and Irena Zivkovic1 | ||
1Department of Electrical Engineering, Technology University of Eindhoven, Eindhoven, Netherlands, 2Department of Electrical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark, 3Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark |
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One of the major challenges in the design of multichannel arrays for UHF MRI is minimizing coupling between elements. Shielded-coaxial-cable (SCC) coils have been recently proposed as highly decoupled elements per se: however, the decoupling mechanism of SCC coils is still not determined. In this work, we examined the relationship between coupling, surface current density uniformity, and the total current on coil conductor through measuring and simulating three different 2-coils arrays. While no correlation was observed between surface current density uniformity and interelement coupling, a negative correlation was observed between the coupling and the total current on coil conductor. |
| 1539 | Computer 89
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Nested Geometrically Decoupled Triple-Tuned Volume Coil for 1H, 23Na and 31P at 4.7T |
| Joseph Busher1, Edith Valle2, Steven M. Wright1,2, and Mary P. McDougall1,3 | ||
1Biomedical Engineering, Texas A&M, College Station, TX, United States, 2Electrical and Computer Engineering, Texas A&M, College Station, TX, United States, 3Electrical and Computer Engineering, Texas A&M, C, TX, United States |
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The use of traps as well as the use of switching circuitry to develop multinuclear coils is well established. However, it is well known that the use of traps introduces undesired losses to one or more nuclei in the structure while switching eliminates applications requiring true simultaneous imaging. As a result, our group developed a triple-tuned volume coil that solely uses geometric decoupling using only two structures. The coil demonstrated homogeneous fields with sufficient decoupling between the structures to acquire multinuclear NMR data. |
| 1540 | Computer 90
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Simulation validation of an 8-channel parallel-transmit dipole array: including RF losses for robust correlation with experimental results |
| Jérémie Clément1 and Özlem Ipek1 | ||
1Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom |
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A method for validation of the simulation model with respect to experimental results is introduced for an 8-channel parallel-transmit dipole coil array. An original approach to include RF losses is described. The simulation results were quantitatively compared to the experimental data in terms of scattering parameters, individual transmit field (magnitude/phase) and combined transmit field. Two distinct configurations, not including RF losses were compared to the proposed approach. High correlation was achieved between simulated and experimental data. We conclude that with the proposed approach for RF losses, a robust validation is achieved for the 8-channel parallel-transmit dipole coil array at 7T. |
| 1541 | Computer 91
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Findings during tuning procedure of a 7T radiofrequency transmit resonator |
| Tiago Martins1 and Tamer S Ibrahim1 | ||
1University of Pittsburgh, Pittsburgh, PA, United States |
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In this work, we explain the tuning procedure for a new conforming Tic-Tac-Toe (TTT) array and the findings that were observed during this procedure. These findings help shape how the array can be used in building a 7 Tesla RF coil system for neuroimaging applications.. It is shown that a 2-channel and 4-channel configurations can be tuned similarly and produce similar magnetic field distribution and intensities. |
| 1542 | Computer 92
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Development of 8-Channel 1H-2H Dual-Frequency loop coil array with LC tanks for 1H MRI and 2H MRS imaging of human brain at 7 Tesla |
| Soo Han Soon1,2, Matt Waks1, Hannes M. Wiesner1, Xin Li1, Xiao-Hong Zhu1, and Wei Chen1,2 | ||
1CMRR, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, 2Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States |
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Deuterium (2H) MRS imaging (DMRSI) enables us to measure both the cerebral metabolic rate of glucose and TCA cycle rate and to image brain tumor with an excellent contrast. It is common to apply two sets of 2H and 1H RF coils for performing DMRSI, resulting in coil complexity and RF interference. We introduce an 8-channel 2H-1H dual-frequency loop coil array with LC tanks, enabling each loop coil being tuned to 2H and 1H resonant frequencies simultaneously. We have constructed a prototype head coil for human brain applications at 7 Tesla and validated the coil via benchtop and imaging tests. |
| 1543 | Computer 93
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Noise Considerations for a Microsolenoid at 15.2T Designed for MR Microscopy |
| Benjamin M Hardy1,2, Yue Zhu1,3, Mark D Does1,4,5, Adam W Anderson1,3,4, and John C Gore1,2,3,4 | ||
1Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 2Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States, 3Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, 4Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 5Department of Radiology and Radiological Science, Vanderbilt University Medical Center, Nashville, TN, United States |
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Magnetic Resonance Microscopy aims to produce micron scale resolution images in reasonable times, but SNR decreases as voxel sizes shrink. RF coils must be optimized and their performance depends on coil resistance and sample size. We compared the relative performance of a commercially available cryogenically cooled surface coil of 24 mm in diameter to a smaller, 1.5 mm diameter, room temperature microcoil at 15.2T. A silver microsolenoid had threefold SNR increase but with decreased FOV and susceptibility artifacts. An optimized microcoil should be able to produce images with 10 µm isotropic resolution within 10 hours with an SNR of 10. |
| 1544 | Computer 94
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Impact of Coupling on the B1+ Field Produced by a 15-panel Tic-Tac-Toe RF Array |
| Andrea N Sajewski1, Tales Santini1, Anthony DeFranco1, Tiago Martins1, Jacob Berardinelli1, Howard J Aizenstein1, and Tamer S Ibrahim1 | ||
1University of Pittsburgh, Pittsburgh, PA, United States |
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We investigated the impact of coupling (magnitude and phase) on the B1+ field distribution and intensity of a 30-channel double-rowed Tic-Tac-Toe (TTT) RF array. We found that by changing the coupling of the TTT coil modules, we are able to modify the B1+ distribution from a single channel and how the B1+ field intensity is spread between different Z levels of the 30-channel array. This effect was seen in both simulations and experimental B1+ maps. |
| 1545 | Computer 95
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Second resonance mode ensure intrinsic low coupling between elements on shielded-coaxial-cable coil designs |
| Sadri Güler1,2, Vitaliy Zhurbenko3, Irena Zivkovic4, Vincent Oltman Boer1, and Esben Thade Petersen1,2 | ||
1Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark, 2Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kgs Lyngby, Denmark, 3Department of Electrical Engineering, Technical University of Denmark, Kgs Lyngby, Denmark, 4Electrical Engineering Department, Technical University of Eindhoven, Eindhoven, Netherlands |
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The recent introduction of the flexible shielded-coaxial-cable coils (SCC) and their intrinsic high degree of decoupling between elements make them ideal for multichannel transceiver arrays needed for improved field homogeneity at ultra-high field MRI. In this work, we show the mode of operation of the SCC and that the selection of its second resonance mode is crucial to obtain its intrinsic high degree of decoupling between elements. We obtained this insight using both numerical simulations and an equivalent circuit model, which can guide to optimal SCC designs in the future. |
| 1806 | Computer 76
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The Feasibility of 3D MR Fingerprinting using Cartesian sampling for isotropic 1mm3 resolution at 0.55T |
| Yun Jiang1, Ruogu Matthew Zhu2, Bo Zhao3,4, and Nicole Seiberlich1 | ||
1Department of Radiology, University of Michigan, Ann Arbor, MI, United States, 2Department of Electrical and Computer Engineering, University of Michigan, Ann Arbor, MI, United States, 3Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, United States, 4Oden Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, TX, United States |
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The purpose of this work is to assess the feasibility of performing MR Fingperprinting with 3D pseudorandom Cartesian sampling for an isotropic spatial resolution of 1mm3 at 0.55T in the brain. |
| 1807 | Computer 77
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Free-Breathing Liver Fat Quantification using Radial Acquisition on a High-Performance 0.55T MRI System |
| Shu-Fu Shih1,2, Sophia X. Cui3, Xiaodong Zhong3, Bilal Tasdelen4, Ecrin Yagiz4, Krishna S. Nayak4, and Holden H. Wu1,2 | ||
1Department of Radiological Sciences, University of California Los Angeles, Los Angeles, CA, United States, 2Department of Bioengineering, University of California Los Angeles, Los Angeles, CA, United States, 3Siemens Medical Solutions USA, Inc., Los Angeles, CA, United States, 4Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States |
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MRI proton-density fat fraction (PDFF) is used for non-invasive diagnosis of fatty liver disease, and has been validated at 1.5T and 3T field strengths. There is renewed interest in lower field strengths, such as 0.55T, because of potential advantages such as lower hardware/siting costs and a larger bore diameter. This study investigated PDFF quantification at 0.55T and validated PDFF quantification at 0.55T using Cartesian and Radial Dixon techniques in a reference phantom, and demonstrated the feasibility of in vivo free-breathing radial liver PDFF quantification in healthy subjects at 0.55T. |
| 1808 | Computer 78
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Random Matrix Theory reconstruction for T1 quantification on a field-cycling scanner for B0 ranging between 2-200mT |
| Gregory Lemberskiy1,2, Vasiliki Mallikourti3, Dmitry S Novikov1, and Lionel M Broche3 | ||
1Radiology, New York University Grossman School of Medicine, New York, NY, United States, 2Microstructure Imaging INC, New York, NY, United States, 3Aberdeen Biomedical Imaging Centre, University of Aberdeen, Aberdeen, United Kingdom |
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We showcase high SNR T1 maps over a range of low field strengths on a stroke patient imaged using a field-cycling imaging scanner (FCI), an MR system capable of varying B0 over 2 orders of magnitude. Images from this scanner are denoised using Random Matrix Theory (RMT), leveraging the redundancy over multiple inversion times and field strengths to increase the baseline SNR by 3-fold. Following RMT denoising, we observe the T1 dispersion effect indicating a deviation of R1 frequency dependence from the BPP theory. |
| 1809 | Computer 79
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Ultra-Fast Water/Fat Imaging of the Abdomen at 0.55T |
| Krishna S. Nayak1,2, Bilal Tasdelen1, Ecrin Yagiz1, and Sophia X. Cui3 | ||
1Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, 2Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States, 3Siemens Medical Solutions USA, Inc., Los Angeles, CA, United States |
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We demonstrate single-breath-hold volumetric water/fat imaging of the abdomen using spiral gradient echo imaging at 0.55T. This provides 4x finer spatial resolution with adequate SNR and spatial resolution to measure the visceral adipose tissue compartment. |
| 1810 | Computer 80
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Initial Evaluation of Neuroimaging at 0.55T |
| Anna Lavrova1, Kathleen Ropella-Panagis1, Nancy Dudek1, Joel Morehouse1, Ryo Kurokawa1, Mariko Kurokawa1, Pedro Itriago-Leon2, Toshio Moritani1, and Nicole Seiberlich1 | ||
1Department of Radiology, University of Michigan, Ann Arbor, MI, United States, 2Siemens Medical Solutions USA Inc., Houston, TX, United States |
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The purpose of this study was to determine which sequences can be immediately deployed for brain and spine imaging on a low-field 0.55T MRI system, with the goal of generating optimized protocols which can be used at other sites for routine clinical neuroimaging. The image quality of 174 brain and spine images was rated by two neuroradiologists. Almost all brain (T1w, T2w, FLAIR, DWI, MRA) and spine (T1w, T2w, DIXON) sequences received image quality scores corresponding to acceptable diagnostic image quality. These sequences form numerous neurological MRI protocols, which based on these results could be collected at 0.55T. |
| 1811 | Computer 81
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T1 and T2 Mapping of the Infant Brain with a Low-Field, Portable MRI System |
| Nathan S Artz1, Maura S Sien1, Amie S Robinson1, Houchun H Hu2, Rafael O'Halloran2, Megan Poorman2, and Sherwin S Chan1 | ||
1Radiology, Children's Mercy Kansas City, Kansas City, MO, United States, 2Hyperfine, Inc., Guilford, CT, United States |
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Low-field, portable MRI offers great potential to improve diagnostic ability in the neonatal intensive care unit. Brain relaxometry will be critical to tune scan parameters at a low magnetic field for infants, whose brain tissue composition is very different than adults. In this study, ten infants were scanned at bedside on a 64mT system. Whole brain T1 and T2 mapping was performed for five infants each. Regions of interest were drawn in the white matter and thalamus for all subjects. Mean T1 and T2 values were 702ms and 294ms for white matter and 364ms and 139ms for the thalamus. |
| 1812 | Computer 82
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Assessing the utility of low-resolution images for Hydrocephalus treatment planning |
| Joshua Harper1, Venkateswararao Cherukuri2, Tom O'Reilly3, Mingzhao Yu2, Edith Mbabazi-Kabachelor4, Roland Mulando4, Kevin N. Sheth5, Andrew G. Webb3, Benjami C. Warf6, Abhaya V. Kulkarni7, Vishal Monga2, and Steven J. Schiff2 | ||
1Engineering Science, Penn State University, State College, PA, United States, 2Penn State University, University Park, PA, United States, 3Leiden University Medical Center, Leiden, Netherlands, 4The CURE Children's Hospital of Uganda, Mbale, Uganda, 5Yale, New Haven, CT, United States, 6Boston Children's Hospital, Harvard Medical School, Boston, MA, United States, 7University of Toronto, Toronto, ON, Canada |
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Brain images of a quality lower than is conventionally acceptable may still be useful for planning hydrocephalus treatment. Low-field MRI is a technology of growing global interest which has the capability of producing images of sufficient quality for treatment planning and is affordable enough to disseminate to rural regions of the world. Though deep learning enhancement of low-quality images does improve CNR and apparent quality, spatial errors of brain and CSF after enhanced reconstruction add significant risk to treatment management and should be avoided. |
| 1813 | Computer 83
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In Vivo T1 Mapping of Neonatal Brain Tissue at 64mT |
| Francesco Padormo1,2, Paul Cawley1, Louise Dillon1, Emer Hughes1, Jennifer Almalbis1, Joanna Robinson1, Alessandra Maggioni1, Daniel Cromb1, Anthony Price1, UNITY Consortium3, Lori Arlinghaus4, Houchun Harry Hu4, Steve Williams3, Shaihan Malik1, Serena Counsell1, Mary Rutherford1, Tomoki Arichi1, A. David Edwards1, and Joseph V. Hajnal1 | ||
1Centre for the Developing Brain, King's College London, London, United Kingdom, 2Medical Physics, Guy's & St Thomas' NHS Foundation Trust, London, United Kingdom, 3Centre for Neuroimaging Sciences, King's College London, London, United Kingdom, 4Hyperfine Inc., Guildford, CT, United States |
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A promising application of ultra-low field portable MRI is neonatal imaging. In this work we show that neonatal brain T1 mapping is viable at 64mT utilising the Hyperfine Swoop portable MRI system. |
| 1814 | Computer 84
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Quantitative MRI measurements for T1 and T2 at 0.064T |
| Kalina V Jordanova1, Michele N Martin1, Karl F Stupic1, Samantha By2, Megan E Poorman2, Rafael O'Halloran2, and Kathryn E Keenan1 | ||
1NIST: National Institute of Standards and Technology, Boulder, CO, United States, 2Hyperfine, Inc., Guilford, CT, United States |
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Increased use of low-field MRI and quantitative MRI suggests a need for accurate quantitative measurements for fields <0.55T. We measure T1 and T2 for normal brain tissues at 0.064T using a Hyperfine scanner. T1 measurements gave a mean of 266±8.4ms for white matter, 358±6.6ms for grey matter; T2 measurements gave a mean of 95.8±2.4ms for combined white matter and grey matter, 794±357ms for CSF. Validation samples are measured on the Hyperfine system and compared to measurements taken on an electromagnet NMR at 0.064T. |
| 1815 | Computer 85
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Postmortem Multiple Sclerosis Brain Lesion Identification at Low Field |
| Sharada Balaji1, Adam Dvorak1, Irene M. Vavasour2,3, Megan E. Poorman4, Hanwen Liu1, Emil Ljungberg5,6, Steve Williams6, Sean Deoni7, Cornelia Laule1,2,3,8, David K.B. Li2, G.R. Wayne Moore3,8,9, Alex MacKay1,2, and Shannon H. Kolind1,2,3,9 | ||
1Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, 2Radiology, University of British Columbia, Vancouver, BC, Canada, 3International Collaboration on Repair Discoveries, Vancouver, BC, Canada, 4Hyperfine, Inc., Guilford, CT, United States, 5Medical Radiation Physics, Lund University, Lund, Sweden, 6Neuroimaging, King's College London, London, United Kingdom, 7MNCH D&T, Bill and Melinda Gates Foundation, Seattle, WA, United States, 8Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada, 9Medicine, University of British Columbia, Vancouver, BC, Canada |
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A single hemisphere of postmortem brain tissue from a subject with multiple sclerosis (MS) was scanned at high (Philips Elition 3T) and low (Hyperfine Swoop 64mT) field strength to determine whether lesions could be detected using a portable low field MRI system. T2-weighted scans were acquired at both field strengths with matching resolutions to assess the impact of low field. Comparisons with a high resolution 3T scan showed that of 17 visible lesions, 11 were seen on the lower resolution 3T and 10 were seen on the 64mT scan, demonstrating the feasibility of lesion detection at low field. |
| 1816 | Computer 86
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Physics-Informed Deep Learning for Image Distortion Correction from B0-inhomogeneities in Low-Field MRI |
| David Schote1, Lukas Winter1, Christoph Kolbitsch1, Felix Zimmermann1, Thomas O'Reilly2, Andrew Webb2, Frank Seifert1, and Andreas Kofler1 | ||
1Physikalisch-Technische Bundesastalt (PTB), Braunschweig and Berlin, Germany, 2C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands |
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A physics-informed deep neural network using a U-Net in combination with a multifrequency interpolation is presented to correct for B0-field image distortions in low-field MRI. Training data is based on 1.5T and 3.0T knee images and realistic measurement-based assumption of SNR and B0-field inhomogeneities from previously constructed Halbach magnets. Significant (p<0.05) improvements are demonstrated applying the suggested methodology to uncorrected images. |
| 1817 | Computer 87
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Simulation Evidence for use of a Denoising Auto-Encoder (DAE) to Improve Ultra-Low Field (64mT) MRI with a High Field (3T) Prior |
| M. Ethan MacDonald1,2, Eremiahs Fikre1,2, Fernando Vega1,2, and AbdolJalil Addeh1,2 | ||
1Biomedical Engineering, Electrical & Software Engineering, Radiology, University of Calgary, Calgary, AB, Canada, 2Hotchkiss Brain Institute, Foothills Medical Centre, Calgary, AB, Canada |
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In this work, the denoising autoencoder is applied to simulated low field, low resolution, low signal-to-noise images and used to recover the high field, high resolution, high signal-to-noise paired image. Different types of noise, gaussian and chi-squared, is added in simulation. We found that the denoising autoencoder worked slightly better for normally disturbed noise, but not in all cases. We found a linear trend between the model performance with RMSE and the standard deviation of the added noise. This work demonstrates the use of simple and robust denoising autoencoder to improve low field MRI. |
| 1818 | Computer 88
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Accelerating Ultra-Low Field MRI with Compressed Sensing |
| David E J Waddington1, Efrat Shimron2, Nicholas Hindley1,3, Neha Koonjoo3, and Matthew S Rosen3,4,5 | ||
1ACRF Image X Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, Australia, 22Department of Electrical Engineering and Computer Sciences, UC Berkeley, Berkeley, CA, United States, 3A. A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 4Department of Physics, Harvard University, Cambridge, MA, United States, 5Harvard Medical School, Boston, MA, United States |
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Portable MRI scanners that operate at very low magnetic fields are increasingly being deployed in clinical settings. However, the intrinsic low signal-to-noise (SNR) ratio of these low-field MRI scanners often necessitates many signal averages, and therefore excessively long acquisition times. Here we propose to improve SNR through optimized k-space undersampling and Compressed Sensing reconstruction. We demonstrate this approach for 6.5 mT ultra-low-field MRI using: (1) retrospective-subsampling experiments with 2x to 4x acceleration; (2) prospectively-subsampled data acquired from a human brain phantom with a 6.5mT MRI. The results exhibit a higher SNR than the traditional averaging method, without increasing scan time. |
| 1819 | Computer 89
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Scan acceleration by oversampling in a 70 mT MRI scanner |
| Fernando Galve1,2, José Miguel Algarín1,2, Teresa Guallart3, Rubén Pellicer4, Eduardo Pallás1,2, José Manuel González3, Yolanda Vives3, Rubén Bosch3, Guillermo López1,2, Juan Pablo Rigla3, José Borreguero3, Alfonso Ríos3, José María Benlloch1,2, and Joseba Alonso1,2 | ||
1MRILab, Institute for Molecular Imaging and Instrumentation (i3M), Spanish National Research Council (CSIC), Valencia, Spain, 2MRILab, Institute for Molecular Imaging and Instrumentation (i3M), Universitat Politècnica de València (UPV), Valencia, Spain, 3Tesoro Imaging SL, Valencia, Spain, 4Physio MRI SL, Valencia, Spain |
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Here we present accelerated images by PhasE-Constrained Over Sampled (PECOS) MRI in our home-made Halbach MRI scanner (70 mT). We show projection images of a phantom obtained in our “PhysioMRI” scanner (Fig. 1(a)), a home-made scanner designed for musculoskeletal imaging at low field strengths. We use cartesian turbo spin echo (TSE) sequence to sample the k-space. Image reconstructions are performed by phase conjugate reconstruction and by PECOS. |
| 1820 | Computer 90
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Evaluation of dynamic 2D-EPI acquisitions for fetal brain tracking with neural networks |
| Sara Neves Silva1, Irina Grigorescu2, Alena Uus2, Johannes Steinweg2, Maria Deprez2, Jo Hajnal2, Kuberan Pushparajah2, Jana Hutter2, and Enrico De Vita2 | ||
1Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 2King's College London, London, United Kingdom |
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Fetal MRI and MRS are often compromised due to unpredictable fetal motion and commonly require multiple repetitions for diagnostic studies. To overcome these limitations, we are working towards developing a deep-learning based automatic MRI fetal motion tracking method. Our method uses, as input, rapid dynamic multi-echo 2D-EPI acquisitions and is based on a 3D U-Net for brain localisation and translational motion parameters estimation for brain tracking. The results show rapid low-resolution acquisitions contain sufficient information to allow automated fetal brain localisation. Our technique can be used to assess fetal movements and to build navigation systems for fetal MRI/MRS. |
| 1895 | Computer 75
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Investigating the detection capability of RSNs with fMRI at a low field scanner equipped with a high-performance gradient |
| Arjama Halder1, Demetrius Riberio de Paula2, William Handler3,4, Andrea Soddu3, and Blaine Chronik1,3,5 | ||
1Medical Biophysics, Western University, London, ON, Canada, 2Radbound University, Nijmegen, Netherlands, 3Physics and Astronomy, Western University, London, ON, Canada, 4xMR Labs, London, ON, Canada, 5The xMR Labs, London, ON, Canada |
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Preliminary evaluation of the feasibility to perform resting state BOLD fMRI at a low field (0.5 T) MR scanners equipped with a high-performance gradient system by investing the detection capability of RSNs at lower field strengths. There was an overall deterioration in the number of detected regions within all RSNs as the tSNR decreased. However, the 0.5 Evry system that will be used for experimental studies offer a better SNR efficiency than the modelled cases considered here suggesting reasonable capability in extracting RSNs that can potentially provide clinical utility. |
| 1896 | Computer 76
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Investigating the effect of reduced TR in detection of RSNs at a low field MR scanner |
| Arjama Halder1, Demetrius Riberio de Paula2, William Handler3,4, Andrea Soddu3, and Blaine A Chronik1,3,4 | ||
1Medical Biophysics, Western University, London, ON, Canada, 2Radbound University, Nijmegen, Netherlands, 3Physics and Astronomy, Western University, London, ON, Canada, 4xMR Labs, London, ON, Canada |
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Initial investigation of effects due to reduced TR on RSNs at a 0.5 T MR scanner. There was a decrease in detected regions within specific networks for the 3 T data as TR was reduced. However, when the tSNR was approximately 17 ignoring the expected decrement of detected regions compared to the 3 T data, there was an increase in positive detection at shorter TR. These result show the possibility of extracting true RSNs for a low field scanner using shorter TRs which can lead to efficient sequence design since T1 is shortened at low fields. |
| 1897 | Computer 77
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Simulated Impact of Gradient Amplifier Noise on Simple 3D Sequences: Preliminary Results |
| Mike Twieg1 | ||
1Hyperfine, Guilford, CT, United States |
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It is often stated, without qualification, that MRI gradient systems must be precise and/or accurate in order to ensure MRI image quality. Some imperfections (delay, eddy currents) have been well-studied and documented, while others such as noise, ripple, and quantization have not. Here we simulate the impact of white noise in the gradient fields with simple cartesian imaging sequences for a numerical brain phantom. Preliminary results suggest that high-performance/high-cost components typically marketed for gradient control are excessive, and much cheaper components could be used without significant drawbacks (NRMSE < 1%), especially for low-field/low-cost systems. |
| 1898 | Computer 78
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Development of a Low Field Tabletop Micro-MRI systemUsing Novel Solid-State Hyperpolarization of Water |
| Emily Buchanan1,2,3, Karl Stupic1, and Stephen Russek1 | ||
1Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, CO, United States, 2Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States, 3Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX, United States |
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Micro-MRI systems could have transformational applications in pathology and personalized medicine if substantial technological challenges are overcome: resolution needs to be improved from current state-of-the-art to subcellular resolution <10$$$\mu$$$m, contrast needs to be improved to allow delineation of cells and cell structures, and systems need to be miniaturized from the large high-field superconducting-magnet systems to low-cost tabletop systems. A key enabling component is likely to be a room-temperature low-field point-of-use hyperpolarization system. Here we present a tabletop 135mT micro-MRI system that uses a novel solid-state point-of-use water proton hyperpolarization system integrated into the imaging cell that functions as a bioreactor. |
| 1899 | Computer 79
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Application of Litz Wires in MRI Coil Design up to 15 MHz |
| Robert Kowal1,2, Ivan Fomin1,2, Marcus Prier1,3, Enrico Pannicke1,2, Georg Rose1,2, and Oliver Speck1,3 | ||
1Research Campus STIMULATE, Otto-von-Guericke University, Magdeburg, Germany, 2Institute for Medical Engineering, Otto-von-Guericke University, Magdeburg, Germany, 3Department for Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany |
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The use of litz wire in their optimized frequency range can provide increased efficiency of high-frequency coils and lead to higher SNR in MR measurements. This work experimentally explores the added value of such a litz wire using equivalent solenoid coils in the range of 1 to 61 MHz. An improvement could be measured up to a frequency of 15 MHz, whereas the maximum effectiveness of the investigated wire was at 3 MHz. In addition, the SNR gain was validated in agreement on an 0.26 T MR system by comparing 1H FID signals. |
| 1900 | Computer 80
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A flexible, 4-channel head array for 0.2T readout FCI (Field-Cycling Imaging). |
| Robert Stormont1,2, James Ross1, Gareth Davies1, Vasiliki Mallikourti1, Amnah Alamri1, Lionel Broche1, and David Lurie1 | ||
1Medical Physics, University of Aberdeen, Aberdeen, United Kingdom, 2GE Healthcare, Waukesha, WI, United States |
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A 4-Channel Head Coil RX Array has been created supporting Field-Cycling Imaging studies at an 8.5 MHz readout frequency. Head imaging to date, has been accomplished with a quadrature TX/RX birdcage coil. The array goals include improved SNR, enhanced patient comfort, peripheral compatibility, with fast application to various sized heads. Evaluation with healthy volunteers is now underway. The array appears well tolerated by individuals when compared to the 8-rung birdcage, accommodating a communication headset, and leaving the face quite open. SNR is comparable to the birdcage at the image center and improved as you move towards the array elements. |
| 1901 | Computer 81
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Optimized radio frequency coil for low-field magnetic resonance relaxometry in human finger |
| Junnan Wang1, Rongsheng Lu1, Layale Bazzi2, Xiaowen Jiang1, Yi Chen1, Zhengxiu Wu1, Qing Yang1, Zhonghua Ni1, Hong Yi1, and Dan Xiao2 | ||
1School of Mechanical Engineering, Southeast University, Nanjing, China, 2Department of Physics, University of Windsor, Windsor, ON, Canada |
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The permanent magnet based low-field and low-cost MR systems increase the accessibility and potential of point-of-care diagnosis, where relaxometry measurement is usually preformed due to the low requirement of B0 field homogeneity. However, inhomogeneous B1 field results in errors in the T2 relaxation times, especially in in-vivo localized human tissue measurements. A novel RF coil termed T coil has been developed to provide a better B1 field homogeneity and more accurate in-vivo relaxation measurements than the conventional coils. This may enable the noninvasive diagnosis of diseases through the human finger measurements with portable and affordable MR systems. |
| 1902 | Computer 82
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Evaluation of a Novel 8-Channel Receive Coil for Speech Production MRI at 0.55 Tesla. |
| Felix Munoz1, Yongwan Lim2, Sophia X. Cui3, Helmut Stark4, and Krishna Shrinivas Nayak1,2 | ||
1Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States, 2Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, 3Siemens Medical Solutions, Los Angeles, CA, United States, 4Stark Contrast, Erlangen, Germany |
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MRI has enabled significant advances in our understanding of human speech production. This application benefits from a lower magnetic field due to reduced off-resonance effects at air-tissue interfaces. Here, we evaluate the SNR and parallel imaging performance of a dedicated speech coil at 0.55 Tesla, and compare it to that of a head-neck coil. Over the upper airway regions of interest, the dedicated coil shows approximately 1.3- to 4.6-fold improvement in SNR efficiency compared to the head-neck coil. |
| 1903 | Computer 83
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Flexible six-channel knee array for MRI at 0.55T |
| Bili Wang1,2, Syed S. Siddiq1,2, Jerzy Walczyk1,2, Mary Bruno1,2, Jan Fritz1,2, Iman Khodarahmi1, Inge M. Brinkmann3, Robert Rehner4, Karthik Lakshmanan1,2, and Ryan Brown1,2 | ||
1Bernard and Irene Schwartz Center 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, 3Siemens Medical Solutions USA Inc., Malvern, PA, United States, 4Siemens Healthcare GmbH, Erlangen, Germany |
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New-generation 0.55T systems require a suite of tailored coils to preserve image quality that is expected from higher field systems. We built a six-channel coil array for knee MRI using RG58 coaxial cable loops, which have adequate mechanical flexibility to wrap tightly around the leg and suitably low conductive loss at 23.55MHz. Initial findings show that the dedicated coil outperformed a general-purpose counterpart and suggest that clinical quality knee imaging is feasible. |
| 1904 | Computer 84
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Phantom Development for Comparison of Thermal Mapping |
| Diego Felipe Martinez1, Curtis N. Wiens2, Amgad Louka3, Dereck Gignac1, Will Bradfield Handler1, and Blaine Alexander 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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Thermal Mapping using MRI is a non-invasive method for probing the body and has both diagnostic and interventional applications. If conducted on more accessible low field strength systems, these can improve the accessibility of the method for wider use. In order to validate and compare thermal mapping, a temperature control phantom was developed with tools for heating the phantom and externally tracking the temperature of the phantom. A heating study was performed with the phantom at two temperatures, and the thermometry methods showed good connection to the change in temperature in the phantom. |
| 1905 | Computer 85
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Design and Optimization of Asymmetrical Tapered RF Solenoid Tx / Rx Coil for Halbach-Array based Low-field MRI Scanner |
| Meena Rajendran1 and Shao Ying Huang1 | ||
1Singapore University of Technology, Singapore, Singapore |
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The optimization of an asymmetrical tapered solenoid coil using multi-objective Genetic Algorithm is presented to achieve high sensitivity, high homogeneity, low inductance simultaneously at 2.84MHz within a cylindrical volume(95×95х10mm). The asymmetrical solenoid coil has a lower half that consists of turns with variable pitches and a constant radius and an upper half that consist of turns with variable pitches and profile curvature(variable radius). Two coil winding patterns are included: single winding and multiple windings at each groove. The optimal design shows a sensitivity of 138 μT/√W (29.7%increase), 3.8% homogeneity reduction, comparable inductance compared to a traditional solenoid of similar dimensions.
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| 1999 | Computer 94
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Automated tuning of gate driver circuit using eGaN FETs |
| Natalia Gudino1 | ||
1LFMI, NIH, Bethesda, MD, United States |
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An automated tuning of the dual resonance LC network that forms the gate driver circuitry of a dual tuned RFPA is presented. Through this automated tuning the RFPA could be adapted from the control to operate at the selected 1H and X-nucleus frequencies. |
| 2000 | Computer 95
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A Calibration and Compensation Method for Dynamic Range Recovery of Low-Power SiGe Pre-Amplifiers. |
| Christopher Vassos1, Fraser Robb2, Shreyas Vasanawala3, John Pauly1, and Greig Scott1 | ||
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2GE Healthcare, Aurora, CO, United States, 3Radiology, Stanford University, Stanford, CA, United States |
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Power consumption reduction is key when exploring wireless MRI arrays. An alternative low-power (5.7mW) SiGe pre-amplifier is presented and its impact on imaging performance evaluated in a benchtop setting. The reduction in power results in a more extreme non-linearity that introduces distortion into the images. It is possible to calibrate and compensate for this distortion through receive-only methods. Applying this compensation to the distorted images results in a restoration of image quality with resulting RMSE comparable to industry standard amplifiers representing a potential power reduction up to 30x. |
| 2001 | Computer 96
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Design of a Miniaturized High Impedance Preamplifier for 7T MRI |
| Saadou Almokdad1, Paul-François Gapais1,2, Michel Luong3, Alexis Amadon1, Elodie Georget2, and Eric GIACOMINI 1 | ||
1CEA Saclay/DRF/JOLIOT/NEUROSPIN/BAOBAB/METRIC, Gif-sur-Yvette, France, 2Multiwave Imaging SAS, Marseille, France, 3CEA Saclay/DRF/IRFU/DACM//LISAH, Gif-sur-Yvette, France |
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Coil arrays enhance human body performance for an MRI measurement both in speed and signal-to-noise ratio. However, size and cabling of such arrays can deteriorate the performance of the imaging, or put at risk the safety of the patient. A miniaturized preamplifier is proposed (dimensions 24mm x 11mm), to be placed directly onto the receive coil. The design needs to preserve a good performance (noise figure ≤ 1dB, gain ≈ 28dB), and provide high impedance to minimize the coupling to nearby coils. |
| 2002 | Computer 97
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Compatibility of a 3D Time-of-Flight Video Camera for Motion Capture with a 0.55T MRI System |
| Douglas Brantner1, Leanna Pancoast1, Jerzy Walczyk1, Roy Wiggins1, Ryan Brown1, and Christopher Collins1 | ||
1Center for Advanced Imaging Innovation and Research, New York University, New York, NY, United States |
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We evaluated compatibility of a 3D Time-of-Flight (ToF) video camera with a 0.55T MRI system. Initial tests showed severe MR image artifacts when the ToF camera was operating, and USB communication with a computer outside the MR suite was interrupted during MR image acquisition. With adequate conductive shielding of the ToF camera and typical MR imaging bandwidths, MR images could be acquired with no measurable effects from the ToF camera, and with no effects of the MRI system on ToF signal acquisition. |
| 2003 | Computer 98
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3D MRI characterization of 3D printed tumor tissue models using a plastronic MR-Bioreactor : Preliminary results |
| Jean-Lynce Gnanago1, Tony Gerges1, Laura Chastagnier2, Emma Petiot2, Vincent Semet1, Philippe Lombard1, Christophe Marquette2, Michel Cabrera1, and Simon Auguste Lambert1 | ||
1Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale de Lyon, CNRS, Ampère UMR5005, Villeurbanne, France, 23d.FAB, Univ Lyon Université Lyon1 CNRS, INSA, CPE-Lyon ICBMS UMR 5246, Villeurbanne, France |
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Tissue engineering for regenerative medicine have been developing for a few decades now and the number of applications is increasing to tackle the shortage of organ donors. To date, only few systems can allow both monitoring and 3D characterization of tissue constructs during their growth. In this study, we decided to focus on following the Apparent Diffusion Coefficient (ADC) known to be a marker of cell density and built a MR-Bioreactor to probe the ADC of a growing tissue. In this preliminary work, we were able to follow the cell density of a tumor tissue model using our dedicated MR-bioreactor. |
| 2004 | Computer 99
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A Wireless Pilot Tone Based Patient Squeeze-Ball (P2TSB) |
| Mario Bacher1, Peter Speier2, and Jan Bollenbeck3 | ||
1MR R&D CFP, Siemens Healthineers, Erlangen, Germany, 2MR DL CARD, Siemens Healthineers, Erlangen, Germany, 3MR R&D HW&SYS CRX, Siemens Healthineers, Erlangen, Germany |
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We developed a prototype wireless patient alarm-ball based on Pilot Tone technology which could speed up patient setup time and increase patient comfort. The use of Pilot Tone as a means of signal transmission enables easy and cost-effective use of this concept on existing scanners with only a minimal software upgrade. |
| 2005 | Computer 100
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Assessing Universal Code Compression to Lower Wireless MRI Data Rates |
| Greig Scott1 | ||
1Electrical Engineering, Stanford University, Stanford, CA, United States |
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For wireless MRI data links employing simple ASK or DPSK binary modulation, there is a need to compress the k-space data to lower data rates and use less spectral bandwidth. We explored Fibonacci and Exp-Golomb universal codes for lossless compression. Our results indicate that compression can reduce rates to 1/3 to 1/4 of the original levels. Actual compression will depend on signal gain, as well as k-space trajectories. These results suggest the development of an MRI codec for future wireless or fiber optic RF coil array data links. |
| 2006 | Computer 101
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Wireless Power Harvesting of the B1 Field During MR Image Acquisition for Pulse Charging of MR-Compatible Batteries |
| Jonathan Cuthbertson1,2, Trong-Kha Truong1,2, Fraser Robb3, Allen W. Song1,2, and Dean Darnell1,2 | ||
1Medical Physics Graduate Program, Duke University, Durham, NC, United States, 2Brain Imaging and Analysis Center, Duke University, Durham, NC, United States, 3GE Healthcare, Aurora, OH, United States |
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A 4-channel power harvesting coil array was developed to allow the energy emitted from RF transmit pulses within the scanner bore during imaging to be converted into DC voltage pulses for recharging MR-compatible batteries, regardless of the scan parameters or imaging pulse sequence. Proof-of-concept experiments in a phantom show that this power harvesting coil array was able to provide energy to a battery during GRE image acquisition for various flip angles and additionally during GRE-EPI, DTI, and MPRAGE image acquisitions. |
| 2007 | Computer 102
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Novel Compact Dual-Band E-Field Generator for MR Safety Testing of Active Implantable Medical Devices |
| Lena Kranold1,2, Myles Capstick1, Tolga Goren1, and Niels Kuster1,2 | ||
1IT'IS Foundation, Zurich, Switzerland, 2Department of Information Technology and Electrical Engineering, ETH Zurich, Zurich, Switzerland |
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A compact dual-band E-field generator for MRI implant safety testing has been developed to produce diverse, well-defined tangential incident E-fields along defined implant test routings for efficient validation of the transfer function of AIMD. The MITS medical implant test system consists of two pairs of electrodes whose relative amplitude and phase are controlled to create E-field conditions at the frequencies corresponding to 1.5 T and 3 T MRI. Simulations of different exposure settings were validated by measurements of the resulting field distributions with an E-field vector probe along the routing paths. |
| 2008 | Computer 103
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Dual Mode Acousto-optic RF Safety Sensor for Electric Field and Temperature Measurement at 1.5T MRI |
| Yusuf Samet Yaras1, Lee W Bradley1, Dursun Korel Yildirim2, Ozgur Kocaturk3, John Oshinski4,5, and F. Levent Degertekin1 | ||
1Mechanical Engineering, Georgia Institute of Technology, ATLANTA, GA, United States, 2Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States, 3Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey, 4Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States, 5Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States |
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Electric field and temperature sensors are essential tools for RF safety assessment of implants during magnetic resonance imaging. In this work, an acousto-optic sensor was used for both local tangential electric field and temperature measurements. The inherent electric field sensitivity of the piezoelectric crystal mechanically coupled to a fiber Bragg grating provides the electric field information while the thermal sensitivity of FBG is used for temperature measurement for dual mode sensing. The sensor was used to measure the electric field concentration around a reference implant with high SNR as well as the temperature rise at the tip of the implant. |
| 2009 | Computer 104
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Wireless reference implant and communication methodology to assess and investigate RF safety and pTx mitigation strategies for AIMDs |
| Berk Silemek1, Frank Seifert1, Bernd Ittermann1, and Lukas Winter1 | ||
1Physikalisch-Technische Bundesanstalt (PTB) Braunschweig and Berlin, Berlin, Germany |
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Parallel transmission (pTx) systems can substantially improve the RF-safety of active implantable medical devices (AIMDs) in MRI. Here, a wireless reference implant is presented to test pTx mitigation strategies of RF induced implant heating. It is demonstrated that the proposed hardware and communication workflow can measure the sensor Q matrix and use this information to mitigate RF induced heating. The proposed setup enables conceptualization and further testing of a safety strategy relying on an implant communicating with a pTx capable MRI to improve RF safety without major restrictions in MR imaging performance. |
| 2010 | Computer 105
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Mitigation of RF-induced heating on realistic deep brain stimulator lead trajectories by wireless sensor Q-matrix and parallel transmission |
| Berk Silemek1, Frank Seifert1, Rüdiger Brühl1, Bastien Guerin2,3, Reiner Montag1, Bernd Ittermann1, and Lukas Winter1 | ||
1Physikalisch-Technische Bundesanstalt (PTB) Braunschweig and Berlin, Berlin, Germany, 2Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States, 3Harvard Medical School, Boston, MA, United States |
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Measurement-based pTx mitigations on realistic DBS lead trajectories are presented based on small, embedded sensors in the implant casing. Sensor Q-matrix measurements are performed and transmitted wirelessly from the implant to the pTx console. Three different DBS implant trajectories at four different locations have been tested showing successful pTx mitigations of RF induced heating in in-vitro. The methodology is conceptually appealing to be investigated further towards a safety strategy, where an implant communicates with a pTx capable MR scanner in order to improve MR safety and MR imaging performance. |
| 2089 | Computer 79
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Sodium Coil dedicated Universal Sensitivity Map for scan time reduction of 7T MR in-vivo Sodium Imaging |
| Sanghoon Kim1, Sai Merugumala1, and Alexander Lin1 | ||
1Radiology, BWH Center for Clinical Spectroscopy, Boston, MA, United States |
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Sodium studies have shown subtle pathophysiologic changes in tissue sodium concentrations (TSC) in the early stage of the various diseases. One of the major challenges with measuring TSC is its low SNR. Phased array coils are used to increase sodium SNR, however, they result in an inhomogeneous receive profile that makes accurate quantitation of TSC difficult. Uniformity correction is thus required and is often done by generating a sensitivity map. A previous approach introduced the concept of utilizing a universal sensitivity map to reduce total scan time. We present an improved universal sensitivity map solution. |
| 2090 | Computer 80
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A Software-based TIAMO approach to enable high resolution large FOV body imaging at 7T ultra-high field |
| Jenni Schulz1, Oliver Kraff2, Harald Quick2,3, and Tom Scheenen1,2 | ||
1Medical Imaging, Radboud UMC, Nijmegen, Netherlands, 2Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany, 3High-Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany |
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Inhomogeneities across large FOVs are problematic at ultra-high field. We propose a software-based TIAMO implementation to enable similar flip angles across the body without hardware interference on the 7T MR scanner. Using an interleaved and complementary CP+/CP2+ excitation scheme, we acquired water-selective and lipid-selective 3D GRE data at high resolution demonstrating homogeneous signal distribution across the pelvis and lower abdomen. |
| 2091 | Computer 81
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Traveling pulses visit 7T Terra sites: Getting ready for Parallel Transmission in routine use |
| Franck Mauconduit1, Aurélien Massire2, Vincent Gras1, Eberhard Pracht3, Marc Lapert2, Ilana Leppert4, Christine Lucas Tardif4, Sugil Kim5, Kamil Uludag6,7, Tony Stoecker3, Mathieu Naudin8,9,10, Rémy Guillevin8,9,10, Alexandre Vignaud1, and Nicolas Boulant1 | ||
1Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-yvette, France, 2Siemens Healthcare SAS, Saint-Denis, France, 3German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, 4Montreal Neurological Institute, McGill University, Montreal, QC, Canada, 5Siemens Healthineers Ltd, Seoul, Korea, Republic of, 6Techna Institute & Koerner Scientist in MR Imaging, University Health Network, Toronto, ON, Canada, 7Center for Neuroscience Imaging Research, Institute for Basic Science & Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Korea, Republic of, 8CHU Poitiers, Poitiers, France, 9LRCOM I3M, University and University Hospital of Poitiers, Poitiers, France, 10Laboratory of Applied Mathematics, UMR CNRS 7348, University of Poitiers, Poitiers, France |
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Parallel transmission universal pulses (UPs) consist of pre-optimized RF pulse solutions mitigating the RF field inhomogeneity problem for a given RF coil. Optimized offline on a database of representative field maps, they are designed to be robust to intersubject variability and spare the user a cumbersome online calibration. Initially designed for the MAGNETOM 7T Classic system from Siemens Healthineers, with the RF coil being strictly identical, this abstract describes the set of transformations on the pulses necessary to meet the MAGNETOM Terra specifications as well as successful in vivo results already achieved at four Terra sites using the same UPs. |
| 2092 | Computer 82
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Parallel Transmit DANTE-SPACE for improved black-blood signal suppression at 7 Tesla |
| Matthijs H.S. de Buck1, James L. Kent1, Aaron T. Hess1, and Peter Jezzard1 | ||
1Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom |
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DANTE-SPACE can be used for visualizing intracranial vessel walls at 7T, where the flow-sensitive signal attenuation of the DANTE preparation simultaneously suppresses signal from the internal blood and external CSF. However, the efficacy of DANTE is reduced for blood moving upstream through the neck due to limited B1+ coverage at 7T. Here, EPG simulations are used to estimate the effect of this limited B1+ coverage on the achieved contrasts. A pTx-based approach which uses separate RF shims for the DANTE-preparation and the SPACE readout to improve the attenuation of blood moving through the neck is proposed, and validated in vivo. |
| 2093 | Computer 83
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Functional MRI of large-scale brain networks involved in motor control using parallel transmission at 7 Tesla |
| Yidi Lu1, Chia-Yin Wu1,2,3, Shota Hodono1,2, Jin Jin2,4, David Reutens1,2, and Martijn A Cloos1,2 | ||
1Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia, 2ARC Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, Brisbane, Australia, 3School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia, 4Siemens Healthcare Pty Ltd, Brisbane, Australia |
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The standing wave artefact affects SNR and contrast of the images in Ultra-high field (UHF) functional magnetic resonance imaging (fMRI). One way to mitigate this effect is to use parallel transmission (pTx). In this study, we evaluate the benefits of pTx for studies that investigate large-scale brain networks involved in motor control. We show that, compared to the standard circularly polarized (CP) mode, activation patterns in the posterior lobule of the cerebellum, produced by a coordinated finger flexion-extension task in both hands, are better captured using subject-specific pTx pulses. |
| 2094 | Computer 84
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Comparison of Nova 1Tx vs 8Tx head coils for routine 7T neuroimaging |
| Belinda Ding1, Catarina Rua1,2, and Christopher T Rodgers1 | ||
1Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom, 2Invicro LLC, A Konica Minolta Company, London, United Kingdom |
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Most 7T MRI sites have two head coils available for neuroimaging: a single-transmit coil and one capable of parallel transmission (pTx, or 8Tx). The 8Tx coil has a circularly polarised (CP) mode, allowing it to play RF waveforms identical to its 1Tx counterpart. This study compares the performance of a 1Tx coil against an 8Tx coil from the same manufacturer for routine neuroimaging. The 8Tx coil gave better B1+ profiles in posterior brain regions which translates into improvements in other imaging sequences. It also enables the inclusion of pTx-enabled sequences. However, more detailed studies are needed before pooling data. |
| 2095 | Computer 85
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Brainstem 7T 1H-MRS: comparison between single-channel (1Tx32Rx) and parallel transmit (8Tx32Rx) coils |
| Carina Graf1, Belinda Ding1, Catarina Rua1,2, and Christopher T Rodgers1 | ||
1Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom, 2Invicro LLC, A Konica Minolta Company, London, United Kingdom |
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7T MRS offers increased SNR and peak separation. Many Siemens 7T sites have both 1Tx32Rx and 8Tx32Rx head coils. Workflow is similar when using the TrueForm/CP+ mode. We compared MP2RAGE and semiLASER 1H-MRS in brainstem in healthy volunteers to identify a preferred coil for future studies. Results: voxelplacement, linewidth, and concentrations were not significantly different. SNRNAA increased 27% and CRLBs for Gln, GABA & GSH trended to be lower for the 8Tx coil. This encourages regular use of the 8Tx32Rx coil for brainstem 1H-MRS and facilitates method development by allowing full pTx sequences to be added on to scheduled examinations. |
| 2096 | Computer 86
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Time-Generalized Biot-Savart Law for $$$B_1$$$, $$$B_1^+$$$, and $$$B_1^-$$$ Field Computations up to 7T MRI |
| Mirsad Mahmutovic1, Sam-Luca JD Hansen1, and Boris Keil1 | ||
1Institute of Medical Physics and Radiation Protection, TH Mittelhessen University of Applied Science, Giessen, Germany |
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Numerous methods for field computations of RF coils have been developed in the past. All these methods are based on Maxwell's equations or their derived wave equation. However, these methods are difficult to implement and not very intuitively to handle. In this work, we have investigated the suitability of the time-generalized Biot-Savart-law for $$$B_1$$$, $$$B_1^+$$$ and $$$B_1^-$$$-field computations. We showed that this method can be easily implemented and that the obtained results are a good approximation when reflections are neglectable. |
| 2097 | Computer 87
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Model validation of a 500 MHz Inductive Resonator for 11.7 T Brain MRI |
| Natalia Gudino1, Jacco A de Zwart2, Peter Van Gelderen2, Stephen J Dodd1, Jeff H Duyn2, and Joe Murphy-Boesch2 | ||
1LFMI, NIH, Bethesda, MD, United States, 2NIH, Bethesda, MD, United States |
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To evaluate safety of a 500 MHz inductive birdcage resonator for human brain MRI at 11.7 T, we compared phantom SAR measurements with predictions based on simulations. On a head-shaped phantom with realistic permittivity and conductivity, good correspondence was achieved in heating distributions when irradiating the phantom with 85 W RF power. The ability to predict SAR at 500MHz with simulation is critical step towards in-vivo MRI at 11.7 T. |
| 2098 | Computer 88
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Comparison of ultra-high field MRI of ancient remains at 9.4T and 3T |
| Agazi Samuel Tesfai1, Johannes Fischer1, Ali Caglar Özen1, Sébastien Bär1,2, Patrick Eppenberger3, Lena Öhrström3, Frank Rühli3, Ute Ludwig1, and Michael Bock1 | ||
1Dept.of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, 2Department of Neurosurgery, Section for Neuroelectronic Systems, University Medical Center Freiburg, Freiburg, Germany, 3Institute of Evolutionary Medicine, Faculty of Medicine, University of Zurich, Zurich, Switzerland |
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Ancient mummified samples have ultra-short T2* which decreases with increasing field strength. Here, image quality and T2* relaxation times are compared for different tissues of a mummified hand between a clinical 3T and a preclinical 9.4T system using a 3D UTE sequence. Although T2* is shorter at 9.4T, image quality was superior to 3T, justifying the benefits of ultra-high fields (UHF). |
| 2177 | Computer 79
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Smart MetaBox: Metamaterial arrangement for volume-homogeneous SNR enhancement |
| Dennis Philipp1,2, Endri Stoja3, Simon Konstandin1, Robin Wilke1, Diego Betancourt3, Thomas Bertuch3, Juergen Jenne1,4, Reiner Umathum1,4, and Matthias Guenther1,2 | ||
1Fraunhofer MEVIS, Bremen, Germany, 2University of Bremen, Bremen, Germany, 3Fraunhofer FHR, Wachtberg, Germany, 4DKFZ, Heidelberg, Germany |
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A metamaterial arrangement that encloses a volume "metaBox" is shown to yield a significant and volume-homogeneous SNR enhancement in 3T MRI. Due to the integration of non-linear components, the structure self-detunes in Tx whilst being resonant in Rx. Fine-tuning capabilities are included in two different prototypes via (i) a manually trimmable capacitor and (ii) a Bluetooth-controlled digital capacitor that allows for a wireless interface. On-bench characterization as well as MRI experiments verify the functionality of the device. Thus, the metaBox is ideally suited for, e.g., imaging of extremities. |
| 2178 | Computer 80
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Parametric Study of High Dielectric Constant Helmet Characterization |
| Parisa Lotfi Poshtgol1, Soo Han Soon2, Michael Lanagan3, Eugene Furman4, Xinlian Chen5, Xin Li2, Xiao-Hong Zhu2, Wei Chen2, and Qing X Yang1 | ||
1Center for NMR Research, Departments of Neurosurgery and Radiology, 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, 4Materials Research Institute, Pennsylvania State University, State college, PA, United States, 5Department of Biomedical Engineering, South China University of Technology, Guangzhou, China |
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Helmets conformal to the human head with high or ultra-high dielectric constant (HDC/uHDC) materials have been shown to enhance the SNR of entire human head along with a receive array. However, the dielectric resonance modes (DRMs) of the helmet have not been studies systematically. This investigation aimed to; 1) describe the characteristics of the DRMs and their RF field distributions; 2) establish the relationships between DRMs and the basic geometric parameters of the helmet using numerical modeling. Understand the DRMs of large uHDC structures are fundamentally important for future applications of uHDC materials for RF field reach. |
| 2179 | Computer 81
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Effect of Dielectric Resonator (DR) Modes on RF-Magnetic Field |
| Parisa Lotfi Poshtgol1, Navid Pourramzan Gandjii1, Michael Lanagan2, Eugene Furman3, Soo Han Soon4, Xinlian Chen5, Saber Soltani6, Xiao-Hong Zhu4, Christopher T. Sica1, Hannes M Wiesner4, Wei Chen4, kamil Ugurbil4, and Qing X Yang1 | ||
1Departments of Neurosurgery and Radiology, College of Medicine, Pennsylvania State University, Hershey, PA, United States, 2Department of Engineering Science and Mechanics, Pennsylvania State University, State college, PA, United States, 3Materials Research Institute, Pennsylvania State University, State college, PA, United States, 4Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 5Department of Biomedical Engineering, South China University of Technology, Guangzhou, China, 6Department of Electrical Engineering, The Pennsylvania State University, State college, PA, United States |
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Dielectric resonators with Ultra-High Dielectric Constant (uHDC) materials possess intrinsic resonance modes that have been used for RF transmission and reception. The resonance modes and conditions of the uHDC discs were studied through computer simulations. We compared the B1+ field and RX-sensitivity when employing cylindrical uHDC discs at both resonant and non-resonant conditions. We showed in this work, to achieve the best focusing effect into phantom, the design with uHDC material should operate around the first TE01δ mode and lower than the second mode TE01δ with the highest permittivity. |
| 2180 | Computer 82
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Improving Diffusion MRI in the Posterior Fossa Using a Wireless RF Array at 7T |
| Akbar Alipour1, Ameen Al Qadi1, Gaurav Verma1, Alan C Seifert1, and Priti Balchandani1 | ||
1BioMedical Engineering and Imaging Institute (BMEII), Icahn School of Medicine at Mount Sinai, Manhattan, NY, United States |
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Ultra-high field (UHF ≥7T) MRI scanners can provide stronger signals than standard field strengths, which boosts signal-to-noise ratio (SNR) for improved diffusion MRI (dMRI). However, at 7T, wavelength effects cause highly inhomogeneous $$$B_1^+$$$ in the human brain, with lower transmit efficiency in the cerebellum and temporal lobes manifesting as signal dropouts in these regions. Recently, we reported a simple approach of using a wireless radiofrequency (RF) array to improve transmit efficiency and signal sensitivity at 7T focusing on the posterior fossa. Here we demonstrate the feasibility and effectiveness of using the RF array for in-vivo dMRI at 7T. |
| 2181 | Computer 83
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Evaluation of an Ultra High Dielectric Constant (uHDC) Package for Enhancement of a Knee Phased Array |
| Christopher T Sica1, Parisa Lofti Poshtgol2, Sebastian Rupprecht3, and Qing X Yang2 | ||
1Radiology, Pennsylvania State University College of Medicine, Hershey, PA, United States, 2Neurosurgery, Pennsylvania State University College of Medicine, Hershey, PA, United States, 33HyQ Research Solutions, LLC, College Station, TX, United States |
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Prior work has explored the use of dielectric materials to enhance imaging of the brain and spine with rectangular blocks. One area that has not been examined to date is knee imaging, where space constraints limit the use of blocks. In this work we evaluate the performance of an ultra-high dielectric constant (uHDC) curved plate (εr ~ 4500) for knee imaging in a clinical array at 3T. SNR gains of 9 to 71% percent were observed across the patella and patellar cartilage. Transmit efficiency increased up to 100% close to the material, with an increase in transmit inhomogeneity. |
| 2182 | Computer 84
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Metasurface-based pad for improving fetal imaging at 3T |
| Viktor Puchnin1, Evgeniy Koreshin1, Anna Kalugina1, Aleksander Efimtcev1,2, Irina Mashchenko2, Wyger Brink3, and Alena Shchelokova1 | ||
1School of Physics and Engineering, ITMO University, Saint Petersburg, Russian Federation, 2Federal Almazov North-West Medical Research Center, Saint Petersburg, Russian Federation, 3Department of Radiology, C.J. Gorter Center for High‐Field MRI, Leiden University Medical Center, Leiden, Netherlands |
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Radiofrequency magnetic field homogeneity improvement and SAR reduction are two essential tasks for fetal MRI at 3T. We demonstrate for the first time that the metasurface-based pad can effectively improve the transmit efficiency while reducing SAR within the entire fetus and fetus brain. The metasurface is assembled from the metal wires loaded with capacitors. Numerical studies of a pregnant woman voxel model in the 9th month covered with the proposed metasurface centered within fetus brain (body) showed 25% (28%) transmit efficiency improvement and up to 9% (2.8%) increased magnetic field homogeneity, while the whole-body SAR was reduced by 1.2 (1.6)-fold. |
| 2183 | Computer 85
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Actively coupled dielectric pads for adaptive B1+ field shimming |
| Paulina Šiurytė1, Friso de Boer1, Can Akgun2, and Sebastian Weingärtner1 | ||
1Imaging Physics, TU Delft, Delft, Netherlands, 2Microelectronics, TU Delft, Delft, Netherlands |
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MRI at high and ultra high field strengths suffers from B1+ inhomogeneities, but B1+ shimming with multiple transmit coils is only available at top-line scanners. Dielectric pads allow for localized B1+ changes, but need to be specifically designed for the scan and anatomy. In this work we explore the use of an actively switchable dielectric device to allow for spatial B1+ correction without the need for multiple transmit coils. Our phantom experiments at 3T show that coupling mini-pockets with barium titanate slurry enables various field configurations that are switchable, localized and significant in magnitude. |
| 2184 | Computer 86
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Investigation of MR visibility control of water-based (CaTiO3) dielectric padding with iron oxide contrast agent in 7T human brain MRI |
| Seulki Yoo1,2, Ji Seong Barg1, Bo-yong Park3,4, and Seung-Kyun Lee1,2 | ||
1Department of Biomedical Engineering, Sungkyunkwan university, Suwon, Korea, Republic of, 2Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Korea, Republic of, 3Department of Data Science, Inha University, Incheon, Korea, Republic of, 4Center for Neuroscience Imaging Research,Institute for Basic Science, Suwon, Korea, Republic of |
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Ultra-high-field MRI provides improved signal-to-noise ratio (SNR) and tissue contrast. However, at the same time, it exhibits stronger RF field inhomogeneity compared to lower-field MRI. Although such inhomogeneity can be mitigated by customized RF coils and parallel transmit methodology, it is often difficult to translate these to clinical use. Recently, a simple and low-cost high dielectric-constant padding has been proposed to improve the quality of 7T brain images in many sequences. Here, we propose a novel approach to suppress the MR visibility of a water-based dielectric padding by controlled addition of iron oxide contrast agent in 7T human brain MRI. |
| 2185 | Computer 87
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Hybrid 3T 8-channel Receive Array Using a Metamaterial Slab and Companion Loop Elements: Comparison to a Conventional Array |
| Léo Rémillard1, Adam Mitchell Maunder1,2, Ashwin Iyer1, and Nicola De Zanche2,3 | ||
1Electrical and Computer Engineering, University of Alberta, Edmonton, AB, Canada, 2Oncology, University of Alberta, Edmonton, AB, Canada, 3Medical Physics, Cross Cancer Institute, Edmonton, AB, Canada |
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Metamaterials (MTMs) have been used as passive elements to improve the receive sensitivity in MRI by enhancing the field locally, but not connected directly as receive elements. We present the design and construction of a novel 2D transmission line based MTM employed as a 4-port element combined with an additional 4-element coil array. Simulation and measurement of receive sensitivity are compared to those of a conventional 8-element coil array covering the same region. The receive sensitivity in a human torso sized phantom is found to be equivalent, while the MTM slab additionally enhances the transmit performance. |
| 2186 | Computer 88
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2nd-order meander dipoles for 7T head coil passive RF shimming |
| Tania del Socorro Vergara Gomez1,2, Roxane Mamberti2, Marc Dubois3, Elodie Georget3, Tryfon Antonakakis3, Alexandre Vignaud4, Frank Kober1, Stefan Enoch2, and Redha Abdeddaim2 | ||
1Aix Marseille Univ, CNRS, CRMBM, Marseille, France, 2Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France, 3Multiwave Imaging, Marseille, France, 4CEA, DRF/Joliot/Neurospin, Université Paris-Saclay & CNRS, Gif-sur-Yvette Cedex, France |
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Active and passive RF shimming approaches have been proposed to diminish the B1+ inhomogeneities commonly found in a birdcage coil at 7T. In a previous work, we have introduced a meander dipole based on two 3rd-order Hilbert fractals as an alternative solution for passive shimming. In this work we optimized their design using six 2nd-order Hilbert fractals. Simulations and in vivo MRI at 7T using these structures showed strong B1+ enhancement in the area between the two meander dipoles whereas B1+ was reduced in regions below and above the fractal pads. |
| 2187 | Computer 89
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Coupling study between two concentric whole-body MRI birdcage coils: towards a whole-body X-nucleus coil |
| Juan Diego Sánchez Heredia1, Wenjun Wang2, Vitaliy Zhurbenko2, and Jan Henrik Ardenkjær-Larsen1 | ||
1Department of Health Technology, Technical University of Denmark - DTU, Kgs. Lyngby, Denmark, 2Department of Electrical Engineering, Technical University of Denmark - DTU, Kgs. Lyngby, Denmark |
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The feasibility of integrating a whole-body X-nucleus birdcage in a wide-bore clinical 3T MR scanner is evaluated. The challenge is that this extension coil has to be tightly fit into the scanner bore, having a diameter just 16 mm smaller than the concentric 1H coil. Different configurations are proposed and evaluated with the purpose of minimizing interaction between the X-nucleus coil and the native 1H body coil of the scanner. Experimental results are in agreement with simulations and demonstrate a 1H coil detuning of 0.4 MHz due to co-integration with X-nucleus birdcage. |
| 2253 | Computer 66
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BraCoil – preliminary performance evaluation of a wearable breast coil array for 3 T MR mammography |
| Lena Nohava1,2, Michael Obermann1, Roberta Frass-Kriegl1, Karyna Isaieva2, Claire Dessale3, Jacques Felblinger2,3, and Elmar Laistler1 | ||
1High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, 2IADI, Inserm, Université de Lorraine, Nancy, France, 3CHRU-Nancy, Inserm, Université de Lorraine, CIC, Innovation Technologique, Nancy, France |
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A dedicated radio frequency coil design for MR mammography needs to optimize sensitivity, reduce scan time, and improve patient comfort to ultimately facilitate diagnosis. We investigate signal-to-noise ratio and parallel imaging performance differences between widely used commercial 16-/18-channel receive coils for breast MRI at 3 T in prone and supine position and an in-house developed 28-channel wearable coil array (“BraCoil”). An SNR gain of up to a factor of 6 with BraCoil was found in this phantom study. |
| 2254 | Computer 67
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Constant-Tissue Model for Comparison of Supine and Prone Breast Coil SNR |
| Jessica Ann McKay-Nault1, Catherine J Moran1, Jeremiah Hess2, Jana Vincent3, Fraser Robb3, Bruce L Daniel1, and Brian A Hargreaves1 | ||
1Department of Radiology, Stanford University, Stanford, CA, United States, 2Department of Bioengineering, Stanford University, Stanford, CA, United States, 3GE Healthcare, Aurora, OH, United States |
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Recent work has developed supine breast imaging for improved correlation with surgery and comfort but will likely require breast-specific coils to maximize the SNR. Comparing prone and supine SNR can be difficult due to substantial deformation between the positions and heterogeneity of the patient population. We measured SNR in a constant-tissue model to reduce dependence on tissue heterogeneity and provide an overall SNR across the volume of interest. We compared SNR of a novel 60-channel supine coil and a standard prone coil. In the cosntant-tissue images, the supine 60-channel coil increased SNR by 33%, 78% and 80% across 3 volunteers. |
| 2255 | Computer 68
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Construction and characterisation of a 7 Tesla flexible body coil with 10 transmit dipoles and 30 receive loops |
| Konstantinos Papoutsis1, Jérémie Clément1, Stephen E Ogier1, Joseph V Hajnal1,2, Vicky Goh3, Gary J R Cook3, and Özlem Ipek1 | ||
1Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 2Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 3Department of Cancer Imaging, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom |
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We present the first continuous 30-channel loop receive coil array combined with the 10-channel dipole parallel-transmit array for 7 Tesla body imaging. Array comprises a flexible anterior part with 6 dipoles and 18 loops, with 35cm longitudinal coverage along with a hard plastic posterior part containing 4 dipoles and 12 loops. Special features were added to help patient comfort and overcome cabling limitations. Simulations with computational human model show adequate B1+ coverage in areas of interest such as the prostate. Phantom images were taken showing promising results. Further development will follow, and human imaging is planned in the near future. |
| 2256 | Computer 69
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Optimization and Analysis of Shielded Loop Resonators towards Modular Coil Arrays |
| Manvitha Sreereddy1, Michael Bock1, and Ali Caglar Özen1 | ||
1Dept. Radiology, Medical Physics, Medical Center - University of Freiburg, Freiburg, Germany |
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Light-weight and flexible RF coil arrays are needed to obtain high SNR which is translated into shorter scan times and to increase patient compliance. Transmission line resonators or shielded loop resonators (SLR) are insensitive to the changes in geometry and form, since the tuning is determined by the length of the transmission line. In this study, we propose two parameters and a test setup to evaluate coaxial cables and relate this to the SLR performance. Modularity is demonstrated on facial coil that can be attached to the face masks. |
| 2257 | Computer 70
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Pycoilib: a free and pedagogical tool for the calculation of self/mutual inductance of coils of arbitrary geometry in python |
| Aimé Labbé1 and Marie Poirier-Quinot1 | ||
1Université Paris-Saclay, CEA, CNRS, Inserm, Laboratoire d'Imagerie Biomédicale Multimodale Paris Saclay, Orsay, France |
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We introduce pycoilib, a python library developed for the computation of self and mutual inductance of coils. The library allows the user to design coils by dividing their three-dimensional geometry into collections of lines, arcs and circles, and by specifying the geometry of the cross-section of the coil wire. In a case study, the self-inductance of a deformable coil is computed as a function of its configuration. Pycoilib has the potential to become a valuable tool for prototyping, as well as teaching. |
| 2258 | Computer 71
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Improving the Flexibility of RF Power-Sharing Networks with High-Power Phase Shifters |
| Stephen E. Ogier1, Shaihan J. Malik1, and Joseph V. Hajnal1,2 | ||
1Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 2Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom |
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A typical parallel transmit system has an equal number of RF power amplifiers individually connected to an equal number of coil elements. When performing B1+ shimming, the maximum B1+ available is limited by single channel amplifier performance. RF networks which allow for power to be shared between transmit channels have been proposed as a way to overcome this limitation, but fixed networks only offer performance gains over limited ranges of relative phases between channels. Adding a high-power phase shifter between a power-sharing network and coil element can combat this, even with only a few bits of resolution. |
| 2259 | Computer 72
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A 4-channel flexible array with integrated B0 shimming for 3 T |
| Bernhard Gruber1,2, Michael Obermann1, Lena Nohava1, Maxim Zaitsev1, Lawrence L. Wald3, Jason P. Stockmann3, and Elmar Laistler1 | ||
1High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, 2A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, Charlestown, MA, United States, 3A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States |
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Integrated B0 shimming capability with RF coil arrays has already shown advantages in dense configurations. For highly flexible arrays this approach is a challenge due to the bulky RF chokes required to bypass the segmenting capacitors of classical loop coils. In this work we present a flexible 4-channel coaxial coil array module with integrated B0 shimming requiring only two RF chokes per shim channel and thereby demonstrate the feasibility of integrating B0 shim capability into flexible arrays. |
| 2260 | Computer 73
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Studying the influence of cryogenic cooling and B0 alignment on Si PIN diode operation in active decoupling circuits |
| Wenjun Wang1, Vitaliy Zhurbenko1, Juan Diego Sánchez Heredia2, and Jan Henrik Ardenkjær Larsen2 | ||
1Department of Electrical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark, 2Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark |
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Si diodes can require elevated forward bias voltage to achieve sufficient forward bias current when they are placed in a strong static magnetic field B0 at cryogenic temperatures. This may disrupt active decoupling circuit operation in cryogenic MRI coils. Diodes may still operate if aligned in a certain way with the B0 field, which is studied in this work. |
| 2261 | Computer 74
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Flexible Receive Array of Parallel-Resonance High-Impedance Coaxial Coils for 13C Imaging |
| Vitaliy Zhurbenko1, Juan Diego Sanchez Heredia1, Wenjun Wang1, and Jan Henrik Ardenkjær-Larsen1 | ||
1Techical University of Denmark, Kgs. Lyngby, Denmark |
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Self-resonant coils are well suitable for flexible array design. The size of such coils is dictated by the RF signal wavelength, which makes the design challenging at low frequencies. In this work, 13C tuning is achieved by combining distributed and lumped capacitance with the self-inductance of an RG-178 coaxial cable. A 1H trap is moved from the coil to the board of the preamplifier for better coil flexibility. The active 13C decoupling circuit is compact and broadband. The approach is used to develop a flexible 8-channel receive array of parallel-resonance coils for 13C-imaging. The array elements exhibit low noise correlation. |
| 2262 | Computer 75
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Effect of Matching Network Losses on preamplifier decoupling circuit topologies at room and cryogenic temperature for 3 T 13C applications |
| Wenjun Wang1, Vitaliy Zhurbenko1, Juan Diego Sánchez Heredia2, and Jan Henrik Ardenkjær Larsen2 | ||
1Department of Electrical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark, 2Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark |
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The SNR performances of a three- and a four-element matching circuit topologies are compared for the case of 3 T 13C imaging. The benefit to SNR of cryogenic cooling is also compared against the choice of matching networks. Results show that while cryogenic cooling can improve the output SNR by 2–3 dB, a less lossy matching network design can improve the SNR performance by 7–8 dB. The importance of matching network design ought not to be dismissed. |
| 2263 | Computer 76
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Combination of screen printed process with electrodeposition steps to drastically improve flexible MRI coils sensitivity |
| Camila Pereira Sousa1,2, Jean-Lynce Gnanago1, Valernst Gilmus1, Tony Gerges1, Philippe Lombard1, Michel Cabrera1, Hugo Dorez2, and Simon August Lambert1 | ||
1Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale de Lyon, CNRS, Ampère UMR5005, Villeurbanne, France, 2Hawkcell, Marcy l'Etoile, France |
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In the last few years, there has been an increasing interest from the scientific community in the fabrication of flexible coils. Several methods can be used for the manufacture of flexible coil, mainly screen-printed coils on flexible substrates. In this work, three different screen printing coils with different layers of silver ink were manufactured and their quality factors were measured on bench. A MR-coil combining screen-printed process with electrodeposition step was also built. The additional manufacture step allowed improving drastically Q factor of our screen-printed coil with more than one order of magnitude while maintaining good flexibility of the substrate. |
| 2264 | Computer 77
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RF Coils for Evaluation of Duchenne Muscular Dystrophy Biomarkers at 4.7 T |
| Edith Valle1, Travis Carrell2, Peter P. Nghiem3, Steven M. Wright1,2, and Mary P. McDougall1,2 | ||
1Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States, 2Biomedical Engineering, Texas A&M University, College Station, TX, United States, 3Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, United States |
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Duchenne muscular dystrophy (DMD) is a debilitating genetic muscle disorder. To study and characterize this disease efficiently, our group has developed a set of custom single-tuned and multi-tuned coils. We have acquired 1H, 23Na and 31P data from 20 healthy and diseased samples. Some of the studied biomarkers have shown clear distinctions between healthy and diseased samples. |
| 2545 | Computer 77
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Detection of Samples Out of Training Distribution: Rejection of Potential Erroneous Local SAR Predictions |
| Ettore Flavio Flavio Meliado1,2,3, Alexander A.J. Raaijmakers1,2,4, P.R. A.J. Luijten1, and C.A.T. A.J. van den Berg2,5 | ||
1Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2Computational Imaging Group for MR diagnostics & therapy, Center for Image Sciences, University Medical Center Utrecht, Utrecht, Netherlands, 3Tesla Dynamic Coils BV, Zaltbommel, Netherlands, 4Biomedical Image Analysis, Dept. Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, 5Department of Radiotherapy, Division of Imaging & Oncology, University Medical Center Utrecht, Utrecht, Netherlands |
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Recognize potential hazardous situations far from the modeled MR examination scenarios is crucial for RF safety applications and especially for deep-learning-based approaches. Last year we presented a Bayesian deep-learning approach for local SAR assessment. This approach allowed accurate local SAR estimations and returned reliable feedbacks on the error/uncertainty of the estimates for the MR examination scenario observed during training. However, it also showed the dangers of using the predicted uncertainty to identify out-of-training MR examination scenarios. In this study, we propose a simple approach to detect/reject potential erroneous local SAR predictions due to out-of-training transmit array and/or anatomical variations. |
| 2546 | Computer 78
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Effects of Intersubject Differences on Scattering Parameters, SAR, and B1+ in a 7T 8ch. Head Coil |
| Benjamin Michael Hardy1,2, Rana Banik1,3, Xinqiang Yan1,4, and Adam W Anderson1,3,4 | ||
1Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 2Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States, 3Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 4Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States |
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Shorter wavelengths and higher frequencies at UHF contribute to complicated electric field distributions and higher power absorption in the human head leading to potential safety concerns. Scattering parameters, local and global SAR, and B1+ fields are calculated in an 8-channel surface loop Tx array simulated over 70 head-and-shoulder models of 10 tissue compartments. RF shimming methods and pulse sequences are analyzed over each model to demonstrate local and global SAR variation in a population. Patient proximity, coil loading and design, patient composition, and RF shim weights contribute to the variations in SAR and B1+ experienced by each subject. |
| 2547 | Computer 79
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Respiratory motion affects peak spatial SAR value and location – impact on safety supervision for 7T cardiac imaging |
| Natalie Schoen1, Frank Seifert1, Gregory J. Metzger2, Oliver Speck3, Bernd Ittermann1, and Sebastian Schmitter1,2 | ||
1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Berlin, Germany, 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 3Department for Biomedical Magnetic Resonance, Otto-von-Guericke University Magdeburg, Magdeburg, Germany |
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Respiratory motion impacts peak spatial specific absorption rate (psSAR) at cardiac UHF MR imaging as shown previously for individual$$$B_1^+$$$shim vectors. Here two saftey supervision modes were compared: a local SAR control mode (SCM) and a channel-wise power control mode (PCM). Results show amplitude and location changes of the psSAR between inhale and exhale and this effect depends on the coil setup, element type and breathing pattern. Respiratory-induced psSAR variations are lower when applying PCM compared to SCM, while PCM is more conservative with respect to the total power allowed. |
| 2548 | Computer 80
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Correction Factor for EPT-based Patient-Specific SAR Maps |
| Jessica A. Martinez1, Alessandro Arduino1, Oriano Bottauscio1, and Luca Zilberti1 | ||
1Advanced Materials Metrology and Life Science, Istituto Nazionale di Ricerca Metrologica, Torino, Italy |
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Specific absorption rate (SAR) values can be obtained using MRI data to calculate the electrical conductivity via Electric Properties Tomography (EPT) and by indirectly obtaining the electric field by the B1+ field. However, only using B1+ will result in incorrect SAR values. In this work, we propose the calculation of a tissue-specific correction factor to mitigate the inaccuracy of SAR. |
| 2549 | Computer 81
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An extended version of the restricted SAR protocol allowing safe in vivo testing of RF coils in an unconditional and flexible way |
| Natalia Dudysheva1,2, Alexis Amadon1, Alexandre Vignaud1, Redha Abdeddaim3, and Franck Mauconduit1 | ||
1CEA, NeuroSpin, Paris-Saclay University, CNRS, Gif-sur-Yvette, France, 2Multiwave Imaging, Marseille, France, 3Fresnel Institute, Aix-Marseille University, CNRS, Marseille, France |
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This work promotes the RF coil elaboration facilitating its in-vivo testing phase. To exclude patient risk, in-vivo studies with each new coil configuration require prior SAR verifications and commission approval lengthening the design process. The so-called “Restricted SAR” (rS) protocol offers a solution to safely use homemade coils in vivo at any development stage without prior validation. This protocol constrains transmitted RF power and automatically respects the SAR safety limits, whatever the SAR distribution. Here, we propose the extended rS protocol with flexible sequence parametrization. This adjustability offers better B0 mapping coverage, optimal B1+-map estimation, and higher spatial image resolutions. |
| 2550 | Computer 82
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New “restricted SAR mode” definition based on a thermal conservative model for relaxed unconditional safe in vivo experiments |
| Natalia Dudysheva1,2, Nicolas Boulant1, Alexandre Vignaud1, and Franck Mauconduit1 | ||
1CEA, NeuroSpin, Paris-Saclay University, CNRS, Gif-sur-Yvette, France, 2Multiwave Imaging, Marseille, France |
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In this work, we propose to extend the capacities of ultra-low SAR protocol used in coil design. A developed restricted SAR protocol holds the worst-case SAR below the threshold by constraining the total transmitted RF power. Since SAR reflects tissue heating, we exploit a conservative thermal model to derive relaxed SAR constraints depending on acquisition time. This enables to extend the options available for sequences played under this mode, including fat suppression, higher image resolution, or decreased TR. |
| 2551 | Computer 83
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Evaluation of SAR and heating in children exposed to a 7T MRI Head Coil |
| Shaihan J Malik1,2, David J Carmichael1, Jeffrey W Hand1, and Joseph V Hajnal1,2 | ||
1Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 2Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom |
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Electromagnetic and thermal simulations of a range of models (body mass 14-70 kg) were performed for a 7T (297MHz) birdcage head transmit coil. Head averaged SAR (hdSAR) was found to be the limiting factor for all cases, and a (weak) negative linear correlation with body mass was observed (i.e. hdSAR increases with decreasing body mass). Thermal simulations with fixed blood temperature (assumes good thermoregulation) predict temperature increases remain within guidelines if SAR limits are respected. If blood temperature is allowed to vary then elevated core temperatures are predicted for subjects with smaller body mass even when SAR limits are respected. |
| 2552 | Computer 84
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Variability of the specific absorption rate in the child’s head using a transmit array head coil at 7T: a simulation study |
| Maya Delbany1, Michel Luong1,2, Laurent Morel3, Jean-Pierre Adam3, Jean-Christophe Joly3, and Vincent Gras1 | ||
1Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, 91191, Gif sur Yvette, France, 2CEA, DRF, IRFU, Gif sur Yvette, France, 3CEA, DAM, Gramat, France |
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In this study, a 3T MRI database is used to create numerical children’s head models in order to study the variability of the specific absorption rate in the head of children at 7T using a transmit array head coil. These numerical models are integrated in a homemade multi-transmit RF coil model and then used to simulate SAR maps in the head using a finite difference time domain solver called GORF. |
| 2553 | Computer 85
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A 16-channel transceiver dipole array for 1H body imaging at 10.5T: Validation and VOP enabled imaging in-vivo |
| Simon Schmidt1, Arcan Erturk1, Xiaoxuan He1, Yigitcan Eryaman1, and Gregory J Metzger1 | ||
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States |
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To realize the increased pTx functionality of a 16-channel transceiver dipole array for body imaging at 10.5T, a validation process was implemented. After quantifying the uncertainty of the RF arrays electromagnetic simulations a total safety factor was determined enabling the implementation of real-time local SAR monitoring on the scanner through use of virtual observation points (VOP). In vivo data was acquired with the VOP enabled power monitoring demonstrating local RF shimming performance with and without local SAR constrained optimizations. |
| 2554 | Computer 86
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Numerical Simulation of Tissue Damage Due to Magnetically Induced Force for Multi-Configuration Passive Medical Devices |
| Zainul Ihsan1, Michael Schwarz2, Mubashir Husain2, and Gregor Schaefers1,2 | ||
1MR:comp GmbH, Gelsenkirchen, Germany, 2MRI-STaR - Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany |
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Numerical simulation was performed to evaluate tissue damage due to magnetically induced (MI) force in 3T Magnetic Resonance (MR) environment for multi-configuration passive medical devices. Static magnetic and mechanical simulations were employed to determine the impact of MI force on the tissue surrounding the implant. The simulation results were used to select the worst-case for passive medical devices and for quantitative assessment of the tissue damage. |
| 2555 | Computer 87
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On the complexity of pTx systems in SAR assessment |
| Johannes Petzold1, Bernd Ittermann1, and Frank Seifert1 | ||
1Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany |
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Different methods for SAR control (SAR limit, phase-agnostic SAR limit, amplitude limit) are evaluated in a simulation study of parallel transmit (pTx) body coil systems (2,4, or 8 channels) at different B0 (0.5T, 1.5T, 3T). Criteria are the necessary safety factors to accommodate for subject variability, and the resulting mean(B1+). Due to the high safety factor necessary for a phase-based SAR limit, its mean(B1+) performance becomes effectively the same as the much simpler to implement amplitude limit. |
| 2556 | Computer 88
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Local SAR management strategies for RF shimming in fetal MRI at 3T |
| Filiz Yetisir1, Esra Abaci Turk1,2, Elfar Adalsteinsson3,4,5, Patricia Ellen Grant1,2,6, and Lawrence L Wald4,7,8 | ||
1Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Boston, MA, United States, 2Department of Pediatrics, Boston Children's Hospital, Boston, MA, United States, 3Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 4Harvard-MIT Health Sciences and Technology, Cambridge, MA, United States, 5Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Boston, MA, United States, 6Department of Radiology, Boston Children's Hospital, Boston, MA, United States, 7Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Boston, MA, United States, 8Department of Radiology, Massachusetts General Hospital, Boston, MA, United States |
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RF shimming (RFS) improves the transmit field for fetal MRI, however, fetal safety is understudied. Previous simulations studied the SARlocal of the standard imaging mode (CP mode) of each subject to inform the safety of RFS. We evaluated two local SAR management strategies which utilize subject-specific models and use either the individual’s CP mode SARlocal as a limit for RFS or the maximum CP mode SARlocal value across 7 subjects. We evaluated the B1+ performance inside the fetus for each strategy. Using the maximum CP mode SARlocal across the population as the SAR limit greatly improves RFS performance. |
| 2557 | Computer 89
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Investigation of the Ability of Slot Element Metallization to Reduce SAR and RF Heating due to Associated Components |
| Dheyaa Alkandari1 and Steven M Wright2 | ||
1Electrical Engineering, Kuwait University, Abdullah Al Mubarak Al Sabah, Kuwait, 2Texas A&M University, College Station, TX, United States |
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Evidence indicates that excess RF power from coil’s associated circuitry could cause injuries to patients. Slot elements have been investigated earlier and demonstrated good potential when used for multi-channel RF coils. Here we investigate the potential of using the extended metallization of slot elements to shield stray electric field generated from RF coil associated circuitry. RF heating experiment was designed to compare the temperature of the phantom with and without using the slot’s extended metallization to shield the associated circuitry. Experimental results demonstrated an observable reduction in the phantom temperature resulting from extending the slots metallization. |
| 2558 | Computer 90
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MR signal conditioning for an electro-optic conversion with a polarization state modulator |
| paul nobre1, Gwenaël Gaborit2,3, Raphael Sablong1, Nadege Courjal4, Florent Behague4, Antoine Coste4, Adrien Godet4, Miguel Suarez4, Lionel Duvillaret3, and Olivier Beuf1 | ||
1Univ. Lyon, INSA-Lyon, Université Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS, UMR 5220, U1206, Villeurbanne, France, 2Université de Savoie, IMEP-LAHC, UMR 5130, Le Bourget-du-Lac, France, 3KAPTEOS, Sainte-Hélène-du-Lac, France, 4Institut FEMTO-ST, UMR CNRS 6174, Université Bourgogne Franche-Comté, Besançon, France |
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The coaxial cables connecting coils to the MRI are subject to many unwanted interactions with RF pulses and with patients’ tissues. Currents flowing on the shielding of the cable can lead to local SAR increase and RF-induced burns. Despite their limitations and the amount of effort to discard them, there is still no satisfying alternative. One of the issue for competing technologies is to safely provide on coil power supply without cables inside the MRI. In this work, we propose to evaluate the feasibility of passive optical conversion and transmission of the signal to the MRI console. |
| 2559 | Computer 91
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Comparison of 2D vs 3D Deep Learning Algorithms to Estimate Temperature Throughout the Human Body |
| Giuseppe Carluccio1, Eros Montin1, Riccardo Lattanzi1, and Christopher Michael Collins1 | ||
1Center for Advanced Imaging Innovation and Research (CAI2R), New York, NY, United States |
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We developed and compared two different Deep-Learning (DL) based approaches to approximating temperature in subject-specific body models. The first involved use of a 2D U-net to predict temperature throughout the body on a slice-by-slice basis, and the second involved use of a 3D U-net to predict temperature in the 3D body. The 3D approach greatly outperformed the 2D approach, and was very fast. |
| 2622 | Computer 63
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Deep brain stimulation patient safety: Effects of patient-based lead trajectories on full-body 3 T MRI |
| Benson Yang1, Maryam Arianpouya2, Aaron Loh3, Gavin Elias3, Artur Vetkas3, Can Sarica3, Brendan Santyr3, and Simon J Graham1,2 | ||
1Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada, 2Medical Biophysics, University of Toronto, Toronto, ON, Canada, 3Surgery, University of Toronto, Toronto, ON, Canada |
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High SAR RF pulse sequences continue to be avoided for patients with implanted deep brain stimulation (DBS) devices, due to the increased risk of injury. Recent studies have shown that DBS lead management can impact electromagnetic behavior and thus, the overall RF heating effects along the implanted device. The present work studied two patient-based DBS lead trajectories using a commercial DBS device with MR-conditional labeling for full-body 3 T MRI, implanted in a novel anthropomorphic phantom. The preliminary results showed temperature elevations that exceed current imaging guidelines remains possible for high SAR RF pulse sequences. |
| 2623 | Computer 64
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What you see is not what you get: localization of Deep Brain Stimulation leads from metal artifacts |
| Noa Beth Nuzov1, Bhumi Bhusal2, Fuchang Jiang1, Joshua Rosenow3, and Laleh Golestanirad1,2 | ||
1Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States, 2Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States, 3Neurosurgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States |
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Deep Brain Stimulation (DBS) implants are implanted into target regions of the brain to treat symptoms of many neurological disorders. Postoperative Magnetic Resonance Imaging (MRI) scans are used to localize DBS leads, however, there are large, distorted artifacts surrounding the leads in the images. This study uses MRI phantoms to investigate the true location of a DBS lead relative to its artifact. The results will help researchers and clinicians know the actual locations of the lead tip and contacts from postoperative MRI scans to confirm the implant is correctly targeting the desired brain area. |
| 2624 | Computer 65
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Significance of Covering Anatomical Variations for Conservative Assessment of Deposited Power of Leaded Implants in Patients |
| Lena Kranold1,2, Tolga Goren1, Sunder Rajan3, and Niels Kuster1,2 | ||
1IT'IS Foundation, Zurich, Switzerland, 2Department of Information Technology and Electrical Engineering, ETH Zurich, Zurich, Switzerland, 3Center for Devices and Radiological Health (retired), FDA, Silver Spring, MD, United States |
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Anthropomorphic computational phantoms are used to numerically estimate the potential envelope of intensity and distribution of induced E-fields in patients undergoing MR examination. The impact of anatomical variation of the phantom on medical implant risk assessment is demonstrated for generic transfer functions and lead trajectories representing pacemaker, DBS, SCS, and cochlear implant routings. Results showed that even when only one generic transfer function was considered, each of the 12 anatomical phantoms represented the worst-case for at least one configuration. Thus, the widest available range of anatomical phantoms must be examined to define a conservative safety envelope. |
| 2625 | Computer 66
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Combined RF & Gradient Injection Network for AIMDs with leads |
| Vincent Hammersen1, Michael Wolff2, Andreas Rennings3, and Gregor Schaefers1,2 | ||
1MRI-STaR GmbH, Gelsenkirchen, Germany, 2MR:comp GmbH, Gelsenkirchen, Germany, 3General and Theoretical Electrical Engineering (ATE), University of Duisburg-Essen, Duisburg, Germany |
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MR safety of AIMD with leads is assessed test procedures defined in ISO/TS10974. This separates the different electromagnetic field interactions into independent test procedures. E.g., malfunction and rectification testing, with gradient and RF injection networks connected to the lead ports of AIMDs. But this does not correspond to "realistic MRI exposures", where a precise combination of RF and magnetic fields is used for imaging. For this reason, a concept is being proposed in which both injection networks are combined to allow a concerted exposure. This allows the simultaneous exposition of any gradient and RF signal combination. |
| 2626 | Computer 67
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Comparison of Gradient Induced Peak E-fields on Simplified and Realistic Body Models |
| Koray Ertan1,2, Paolo Decuzzi2, Peter B Roemer3, and Brian Rutt1 | ||
1Department of Radiology, Stanford University, Stanford, CA, United States, 2Laboratory of Nanotechnology for Precision Medicine, Italian Institute of Technology, Genoa, Italy, 3Roemer Consulting, Lutz, FL, United States |
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Either peak E-fields on simple geometries with uniform interior properties as suggested by IEC or coupled E-field and neurodynamic simulations on realistic body models can be employed in PNS optimal gradient coil design. Magneto quasi-static simulations were performed to compare the magnitude and location of the peak E-fields in uniform interior body models with smoothed or realistic surface features to fully heterogeneous Virtual Family models. Although peak E-fields are higher on the heterogeneous body models due to complex tissue interfaces, simplified and/or homogeneous models represent a more practical and robust approach predicting population-wide PNS performance. |
| 2627 | Computer 68
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Continuous monitoring of MRI staff exposure to stray magnetic field at 1.5 T and 3 T |
| Angelo Galante1,2,3, Valentino Vito3, Elia Braggio4, Roberta Milanesi4, Vincenzo Giugno5, and Marcello Alecci1,2,3 | ||
1Consiglio Nazionale Ricerche - Istituto SPIN, L'Aquila, Italy, 2Istituto Nazionale Fisica Nucleare - Laboratori Nazionali del Gran Sasso, L'Aquila, Italy, 3Università dell'Aquila, L'Aquila, Italy, 4Tecnorad SrL, Verona, Italy, 5Azienda Sanitaria Locale 1 - Abruzzo, L'Aquila, Italy |
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We show how to monitor the MRI staff exposure to the $$$B_0$$$ stray-field. Monitoring is extended to several body districts without interferences with normal hospital operative procedures. The Weighted Peak index is calculated, for different Action Levels limits as from the current EU regulations, to consider the non-sinusoidal nature of exposure. Results show that exposure limits are exceeded even at 1.5 T and their occurrences significantly increase at 3.0 T scanners. |
| 2628 | Computer 69
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Excitation vector optimization for safe parallel transmission MRI of passively conducting implants in the presence of motion |
| Mostafa Berangi1,2,3, Andre Kuehne1, Helmar Waiczies1, and Thoralf Niendorf1,2,3 | ||
1MRI.TOOLS GmbH, Berlin, Germany, 2Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrück Center for Molecular Medicine in the Helmholtz Association, berlin, Germany, 3Charité – Universitätsmedizin Berlin, berlin, Germany |
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MRI aided monitoring of (biodegradable) passively conducting implants is challenged by transmission field inhomogeneities and potential elevation of RF power deposition (SAR) in the vicinity of an implant. Small movements of an implant with respect to the RF transceiver constitute another potential risk factor for clinical MRI. Recognizing this challenge and the opportunities, this work uses a multi-objective genetic algorithm (GA) to examine the feasibility of excitation vector optimized parallel transmission in the presence of small variations in implant position/orientation. The GA approach provided excitation vectors that meet the safety guidelines for SAR in close vicinity of a (biodegradable) passively conducting implant and that are immune to small changes in the relative position between the implant and the RF transceiver. Our findings are not limited to the specific implant configurations and experimental setups used in this study but provide the technical foundation to derive a generalized transfer function. |
| 2629 | Computer 70
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When they go high, go low? (Maybe, but not so fast): Comparing RF heating of active implantable medical devices in 0.55 T vs. 1.5 T horizontal scanners |
| Pia Panravi Sanpitak1, Bhumi Bhusal1, Bach Nguyen1, Fuchang Jiang2, Ehsan Kazemivalipour3,4, Giorgio Bonmassar3,4, Julie Pilitsis5, Joshua Rosenow6, Gregory Webster7, Andrada Popescu8, Daniel Kim1, and Laleh Golestanirad1,2 | ||
1Department of Radiology, Northwestern University, Chicago, IL, United States, 2Department of Biomedical Engineering, Northwestern University, Evanston, IL, United States, 3A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 4Harvard Medical School, Boston, MA, United States, 5Department of Neurosciences & Experimental Therapeutics, Albany Medical College, Albany, NY, United States, 6Department of Neurosurgery, Northwestern University, Chicago, IL, United States, 7Division of Cardiology, Department of Pediatrics, Northwestern University, Chicago, IL, United States, 8Department of Medical Imaging, Lurie Children's Hospital, Chicago, IL, United States |
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Low-field Magnetic Resonance Imaging (MRI) systems are gaining traction, but their impact on radiofrequency (RF) heating of elongated implants is unclear. The RF heating of conductive lead models with realistic trajectories was examined inside a 1.5 T MRI coil and a 0.55 T Wide Bore MRI coil. 0.1g-SAR was recorded at the tips of conductive implanted leads in adult patients with deep brain stimulation (DBS) systems and pediatric patients with cardiac implants, at both chest and head landmarks. In some instances, heating was higher in the 0.55 T coil, so caution must be exercised before promoting low-field coils as "implant-friendly". |
| 2630 | Computer 71
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Study of Subjective Tolerance during 5T Whole-Body MRI Examinations |
| Xuchen Zhu1, Wenbo Sun2, Shuo Zhu3,4, Zhenhua Shen1, Lan Lan2, Shihong Han1, Shuheng Zhang1, Zhang Shi3,4, Qi Liu5, Yongquan Ye5, Liang Liang3,4, Haibo Xu2, and Liang Liu1 | ||
1United Imaging Healthcare, Shanghai, China, 2Department of Radiology，Zhongnan Hospital of Wuhan University, Wuhan, China, 3Department of Radiology, Zhongshan Hospital, Fudan University, Shanghai, China, 4Shanghai Institute of Medical Imaging, Shanghai, China, 5UIH America, Inc., Houston, TX, United States |
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Questionnaires on subjective feeling were collected and analyzed from 202 subjects following whole-body MRI examinations at 5T. No intolerable discomfort was reported, indicating whole-body examinations at 5T is safe when necessary safety protocols were followed. |
| 2631 | Computer 72
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Implant heating in muscle-mimicking phantoms: an in silico evaluation of perfusion cooling |
| Amgad Louka1,2, William Bradfield-Handler2,3, and Blaine Chronik1,2,3 | ||
1Medical Biophysics, Western University, London, ON, Canada, 2The xMR Labs, Western University, London, ON, Canada, 3Physics & Astronomy, Western University, London, ON, Canada |
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We have developed a novel perfusion phantom and this work describes the simulated RF-heating of a 10 cm titanium rod inside this phantom when placed inside the current gold standard (ASTM) phantom, and our geometry/muscle-mimicking phantoms. Simulations show a 30-45% decrease in observed heating due to perfusion cooling, and once these simulations are experimentally validated they could pave the way for improved acceptance criteria and ultimately improved patient access to MRI |
| 2632 | Computer 73
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Analytical Evaluation of Radio-Frequency Energy-Induced Heating in a Hot Spot without perfusion |
| Mikhail Kozlov1 and Nicolas Boulant 2 | ||
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-Sur-Yvette, France |
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We derived analytical steady-state and transient solutions for a sphere and a SAR source with uniform and the Gaussian distribution located in an infinite medium of homogeneous properties. The results obtained analytically showed that even without taking into account blood perfusion (i) if power deposition is present only in a sphere that encloses 10 gram of human tissue and SAR10g=10W/kg the steady-state temperature rise is below 3°C for power deposition distributions as sharp as Gaussian with σ=R/3=4.33mm, (ii) the sharper the Gaussian distribution of power deposition, the higher Tmax(t=+∞) and the faster it will approach steady-state. |
| 2633 | Computer 74
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Assessment of Femur Metallic Implant Safety at 3T |
| Amira Trabelsi1,2,3, Megdouda Benamara4, Pierre Jomin1, Stefan Enoch1, Marc Dubois4, Martine Pithioux3, David Bendahan2, and Redha Abdeddaim1 | ||
1Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France, 2Aix Marseille Univ, CNRS, CRMBM, Marseille, France, 3Aix Marseille Univ, CNRS, ISM, Marseille, France, 4Multiwave Imaging, Marseille, France |
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We assessed electromagnetic behavior of metallic implant used for distal femur fracture in typical MRI situation. |B1+| field, SAR and temperature variations were computed at 3T using a surface coil on human model for different positions of the implant relative to the coil. To validate the simulation, we measured the E-field and compared it to simulated E-field. |B1+| field maps showed an interesting augmentation near the implant. Both global SAR and local SAR levels proved that it is possible to safely image bone repair. However, temperature elevation near the tip of the implant was important and is to be considerate. |
| 2634 | Computer 75
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Virtual precision surgery for mri implant safety |
| Oriano Bottauscio1, Alessandro Arduino1, Fabio Baruffaldi2, Mario Chiampi1, Jessica Martinez1, Umberto Zanovello1, and Luca Zilberti1 | ||
1Advanced Materials Metrology and Life Science, Istituto Nazionale di Ricerca Metrologica, Torino, Italy, 2IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy |
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In silico evaluation of heating during an MRI exam for patients with passive implants patients need detailed anatomical models to reproduce in vivo scenarios. A quantification of the influence of the model approximation is fundamental to define the main requirements of the digital model.Here, we analyze the impact of different model approximation in simulating RF and gradient-induced heating caused by orthopedic implants. It was found that, whereas the heating due to switched gradient fields does not strictly require the adoption of advanced virtual surgery, the heating caused by RF is strongly affected by the precision of the digital model. |
| 2635 | Computer 76
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Dependence of Electromagnetic Exposure on Design and Excitation Positions of 3T Two-Channel Whole-Body Birdcage Coils |
| Mikhail Kozlov1, Wolfgang Kainz2, and Manuel Murbach3 | ||
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2U.S. FDA, CDRH, Office of Science and Engineering Laboratories, Division of Biomedical Physics, Silver Spring, MD, United States, 3EMConsulting, Zurich, Switzerland |
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The safety assessment of RF exposure in MRI heavily relies on electromagnetic simulations. As there are numerous different coil designs on the market, this assessment is typically performed with sets of generic coil geometries to cover the commercially available bore diameter and coil lengths. This abstract investigated the effect of other design parameters, which are currently less considered. Our results show that feed-port positioning and non-ideal tuning of the coil may considerably alter the RF absorption pattern in an oval phantom, and even more so the E-field distribution outside the phantom. |
| 2636 | Computer 77
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MR Safety of Inductively-coupled and Conventional Intra-oral Coils |
| Agazi Samuel Tesfai1, Simon Reiss1, Thomas Lottner1, Andreas Vollmer2, Michael Bock1, and Ali Caglar Özen 1 | ||
1Dept. of Radiology, Medical Physics, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, 2Department of Oral and Craniomaxillofacial Surgery, Center for Dental Medicine, University Medical Center Freiburg, Freiburg, Germany |
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Intraoral coils (IOCs) increase the signal-to-noise ratio in dental MRI exams several times over external coils. However, the intraoral coil placement might be associated with safety hazards such as RF heating. This study evaluates the safety of different IOCs using temperature and E-field measurements to detect temperature hotspots. An inductively-coupled and a wired IOC were constructed, E-field hotspots were detected and the temperature increase was measured showing that it remains below 1K over 6min RF exposure. |
| 2721 | Computer 85
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Developing 3D-printed phantoms for quality assurance and validation of quantitative DCE–MRI measurements |
| Muhammad Sulaiman Sarwar1,2, Antoine Vallatos1,3, Cher Hon Lau4, Adam Waldman1,3, Simone Dimartino2, and Michael J Thrippleton1,3 | ||
1Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, United Kingdom, 2Institute for Bioengineering, The University of Edinburgh, Edinburgh, United Kingdom, 3Edinburgh Imaging, The University of Edinburgh, Edinburgh, United Kingdom, 4Institute for Materials and Processes, The University of Edinburgh, Edinburgh, United Kingdom |
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Difficulties in engineering accurate biomimetic phantoms make it challenging to validate MRI models. This is particularly true for quantitative vascular permeability measurements using dynamic contrast-enhanced (DCE-) MRI, where no robust controllable phantoms are available for validating novel techniques and harmonising multicentre results. We developed 3D-printed biomimetic vascular permeability phantoms with controllable properties and assessed their ability to interrogate common DCE model quantification approaches. Parameters such as blood flow, vascular permeability, plasma volume and extravascular volume were reproduced by adapted 3D-printed material and flow circuit properties. The resulting phantoms were shown to reproduce realistic DCE-MRI signals observed clinically. |
| 2722 | Computer 86
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Analysis of variability of diffusion tensor imaging measurements using co-electrospun fibre phantom |
| Fenglei Zhou1,2, Fei Gao3, Longji Xu3, Jing Yang3, Fuxin Ren3, Weibo Chen4, and Geoff JM Parker1,5 | ||
1Centre for Medical Image Computing, University College London, London, United Kingdom, 2School of Pharmacy, University College London, London, United Kingdom, 3Department of Radiology,Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China, 4Philips Heathcare, Shanghai, China, 5Bioxydyn Limited, Manchester, United Kingdom |
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Brain diffusion tensor imaging (DTI) measurements are sensitive to pathological changes, but in order for them to be of greatest use it is vital to understand intra-scanner and inter-scanner variations in DTI metrics. Here we demonstrate a physical phantom with variable pore sizes and fibre orientation that can be used to assess the repeatability and reproducibility of DTI measurements across scanners and protocols and present its application in assessing 9 separate scanner/protocol combinations. |
| 2723 | Computer 87
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Microscopically Anisotropic and Randomly Oriented 3D Printed MRI Phantom for Size, Orientation, and Anisotropy Validation in Diffusion Imaging |
| Velencia Witherspoon1, Michal Komlosh1,2,3, Dan Benjamini1,2,3, Peter Basser1,3, and Nick Lavrik4 | ||
1Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States, 2Center for Neuroscience and Regenerative Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States, 3The Henry M. Jackson Foundation for the Advancement of Military Medicine (HJF), Bethesda, MD, United States, 4The Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory (ORNL), Oakridge, TN, United States |
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Microscopically anisotropic but globally isotropic DTI MRI phantom was designed and fabricated using a 2 Photon Nanoscribe 3D Printer. The capillary array blocks were measured aligned and randomly oriented to determine the ability of ddPFG and DTI to characterize local anisotropy in a globally isotropic system. These experiments combined computational methods can provide MRI phantoms that can be employed to validate novel or proposed microstructure imaging experiments. |
| 2724 | Computer 88
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Investigation of sodium alginate- and polyvinyl alcohol-based anisotropic hydrogel phantoms for calibration applications by DWI at 0.6 T |
| Weronika Mazur1,2, Anna Stefańska-Bernatowicz2, Ewa Stodolak-Zych3, and Artur Tadeusz Krzyżak2 | ||
1Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Kraków, Poland, 2Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland, 3Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Kraków, Poland |
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Anisotropic hydrogels has been attracting attention for biomedical purposes. These highly-hydrated materials have potential for tissue-mimicking and then, may serve for advanced medical imaging studies. In the work, we present two types of anisotropic hydrogels made from sodium alginate (NA) and polyvinyl alcohol (PVA) in the form of fiber bundle- a single component for larger phantom. We investigated their potential for diffusion-weighted imaging. NA-based phantoms are characterized by highly uniform diffusivity distribution, even higher then water. Single component turned out to be insufficient for the accurate quantification of the microstructure. PVA-based phantom exhibited desirable diffusion properties for tissue-mimicking. |
| 2725 | Computer 89
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Soy lecithin: a phantom material for the adjustment of apparent diffusion coefficient in magnetic resonance imaging |
| Victor Fritz1, Petros Martirosian1, Jürgen Machann1,2, and Fritz Schick1,2 | ||
1Department of Diagnostic and Interventional Radiology, University of Tuebingen, Germany., Section on Experimental Radiology, Tuebingen, Germany, 2Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich at the University of Tuebingen, Tuebingen, Germany |
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The aim of this work was to systematically investigate whether lecithin is suitable for the construction of a diffusion phantom that covers and simulates ADC-values occurring in human tissue. For this, aqueous solutions of different lecithin concentrations (0%-10%) were prepared and measured by DWI. The presented results showed that lecithin is a suitable agent for simulating a wide variety of ADC-values. Even low concentrations showed a strong decrease in the ADC-value of water. However, with increasing concentration, lecithin also showed a strong influence on T2, so that ADC and T2 cannot be set independently from one another in lecithin-based phantoms. |
| 2726 | Computer 90
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Large-scale simulations to create large collections of realistic white matter samples using MEDUSA |
| Alexis Brullé1, Anas Bachiri1, Christophe Destrieux2, Gilles Wiber3, Thierry Delzescaux 4, Ivy Uszynski1, and Cyril Poupon1 | ||
1BAOBAB/NeuroSpin, Université Paris-Saclay, CNRS, CEA, Gif-sur-Yvette, France, 2iBrain U1253, Université de Tours, CHU Bretonneau, INSERM, Tours, France, 3DSSI, DIF, DAM, CEA, Bruyères-le-Châtel, France, 4LMN, MIRCen, Université Paris-Saclay, CNRS, CEA, Fontenay-aux-Roses, France |
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In this work, we demonstrate that the MEDUSA simulator can be used to create huge collections of brain white matter tissue microstructure samples in the frame of large-scale HPC simulation campaigns and how these Big Data could serve the design of novel computational models able to decode white matter microstructure. |
| 2727 | Computer 91
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Fabrication of an Anthropomorphic, In-Vitro Liver Flow Phantom for Use in Motion-Robust MRI Sequence Validation Experiments |
| James Rice1,2, Ruiqi Geng2,3, Diego Hernando2,3,4,5, and Alejandro Roldan-Alzate1,2 | ||
1Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, United States, 2Radiology, University of Wisconsin-Madison, Madison, WI, United States, 3Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, 4Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, United States, 5Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States |
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A major limitation of standard diffusion-weighted imaging (DWI) in the various organs, including the liver, is the presence of artifacts, bias, and poor reproducibility resulting from physiologic cardiovascular-induced motion. Recent efforts to develop motion-robust DWI sequences show promise, but there is an important unmet need for highly controlled validation in motion phantoms. This study presents the fabrication of an anthropomorphic liver flow phantom that can produce compressive motion in the liver to generate and control artifact seen in DW images. This phantom may enable improved validation of motion-robust DWI and other motion-robust applications. |
| 2728 | Computer 92
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MR-visibility and relaxation properties of 3-D printed FDM polymers |
| Teemu Tuomainen1, Antti Paajanen1, and Mikko J. Nissi1,2 | ||
1Department of Applied Physics, University of Eastern Finland, Kuopio, Finland, 2Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland |
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Increasing availability and affordability of 3-D printers utilizing fused deposition modeling (FDM) have enabled their widespread use especially in pre-clinical MRI, allowing in-house design and manufacturing of elaborate coil housings, animal holders, sample holders, etc. Here, we investigated ten common and broadly available FDM polymers for their MRI-visibility at 9.4T. We utilized ultra-short echo time imaging sequences, specifically, single-point-imaging (SPI) and multi-band SWIFT to measure the relaxation properties of the different polymers. The findings support the selection of appropriate printing materials when either visibility or invisibility for ultra-short echo time imaging is required. |
| 2729 | Computer 93
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Comparing geometric accuracy in MRI using a 3D printed distortion phantom |
| Alex Barrett1 and Marc Rea1 | ||
1Medical Physics, Clatterbridge Cancer Centre NHS Foundation Trust, Liverpool, United Kingdom |
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Distortion in MRI can have a significant impact on diagnosis and radiotherapy treatment planning. We have 3D printed a large, low cost phantom that we used along with a CT ground truth to measure 6 MR scanners geometric accuracy. We found significantly more distortion for the 3T and mobile scanners tested which we conclude means they would require a more careful evaluation of distortion if they are to be used for radiotherapy applications and that care should be taken for all scanners where specialist radiotherapy applications such as stereotactic radiosurgery are used. |
| 2730 | Computer 94
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A protocol for the acceptance tests of an ultra-high field MR system, in compliance with new standard IEC 62464-1:2018 |
| Laura Biagi1,2, Paolo Cecchi2, and Michela Tosetti1,2 | ||
1Laboratory of Medical Physics and Magnetic Resonance, IRCCS Stella Maris, Pisa, Italy, 2Imago7 Research Foundation, Pisa, Italy |
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The European Standard IEC 62464-1:2018 [1] describes the methodologies to carry out acceptance and constancy tests of an MR scanner. Its come into effect extends its applicability in the range of ultra-high field (UHF) tomographers. Here, we present a protocol, with an effective time of acquisition of about 11 hours, developed for the testing of a 7T MR system, in order to address all the requirements of the standard for the evaluation of essential image quality parameters. The protocol provided for the test of two different coil configurations, using proper phantoms. |
| 2731 | Computer 95
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B0 Inhomogeneity Characterization and Correction on an open bore MRI-Linac |
| Shanshan Shan1,2, Paul Liu1,2, David Waddington1,2, Bin Dong2, Mingyan Li3, Fangfang Tang3, Gary Liney2, Feng Liu3, Paul Keall1,2, and Brendan Whelan1 | ||
1ACRF Image X Institute, University of Sydney, Sydney, Australia, 2Ingham Institute For Applied Medical Research, Sydney, Australia, 3School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Australia |
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MRI-Linac systems require high fidelity geometric information to localize and track tumors during radiotherapy treatments. B0 field inhomogeneity causes image distortions and can provide inaccurate tumor anatomy. Here, we develop a high-order spherical harmonic method to correct for B0 inhomogeneity induced geometric distortions. Experimental data acquired from a 1T open bore MRI-Linac was used to validate the proposed method. |
| 2732 | Computer 96
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Convection triggers local MR signal loss during proton beam irradiation of liquid water phantoms |
| Juliane Peter1,2, Sebastian Gantz1,2, Leonhard Karsch1,2, Jörg Pawelke1,2, and Aswin Hoffmann1,2,3 | ||
1OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, 2Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology – OncoRay, Dresden, Germany, 3Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany |
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MRI-based proton beam visualisation in water has proven feasible in exploratory irradiation experiments performed on a first research prototype in-beam MRI system. Beam-induced convection was hypothesised to be implicated into MR signal loss observed within the beam volume. In this study, this hypothesis was tested in liquid water-filled phantoms by suppression of convection-induced motion using mechanical barriers and temperature control of water expansivity. In absence of convection-induced motion, no beam-induced signal changes occurred, supporting the hypothesis that convection triggers local MR signal loss during proton beam irradiation. The elucidation of the exact mechanism of convection-induced signal loss requires further investigation. |
| 2864 | Computer 109
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Acceleration Methods to Acquire Fast 3D Multi-Channel Absolute B1+ Maps at 7T for 8-Channel pTx |
| James L. Kent1, Ladislav Valkovic2,3, Iulius Dragonu4, 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, University of Oxford, Oxford, United Kingdom, 3Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia, 4Siemens Healthineers, Frimley, United Kingdom |
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Ultra-high field MRI with parallel transmit offers significant advantages but B1 transmit maps must be acquired to utilize its full potential. Acquiring absolute B1+ maps for each channel is a time-consuming process and limits the application of UHF to clinical practice. We compare two methods of accelerating the transmit mapping procedure to obtain fast volumetric multi-channel maps for an 8-channel transmit array. Both methods make use of a low-rank reconstruction (TxLR) from undersampled data and a modified pre-saturation TurboFLASH (satTFL) B1+ mapping sequence in combination with either Fourier encoding or a B1TIAMO style acquisition. |
| 2865 | Computer 110
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Interferometric, Hybrid, and Weighted $$$B_1^+$$$ Mapping for Expedited RF Calibration of Parallel Transmit Ultrahigh-Field MRI |
| Dario Bosch1,2, Fabian Müller1, and Klaus Scheffler1,2 | ||
1Magnetic Resonance Center, MPI for Biological Cybernetics, Tuebingen, Germany, 2Department for Biomedical Magnetic Resonance, University Tuebingen, Tuebingen, Germany |
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With an increasing number of transmit channels, faster methods for acquiring $$$B_1^+$$$ maps on pTx MRI systems grow in importance. We compared different interferometry modes for accurate absolute $$$B_1^+$$$ mapping using satTFL. We also introduced weighted hybrid $$$B_1^+$$$ mapping as an attempt to improve hybrid $$$B_1^+$$$ mapping. In this, a second absolute $$$B_1^+$$$ map was introduced as an attempt to further shorten measurement duration while keeping acceptable accuracy. From the tested interferometry modes, phase-cycling performed best in both absolute and weighted mapping. Weighted hybrid mapping exceeded conventional hybrid mapping substantially and could therefore be sufficiently accurate for many applications. |
| 2866 | Computer 111
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Improved B1+- and resonance offset-robust slice-selective inversion pulses |
| Christina Graf1, Adam Berrington2, Martin Soellradl1, Armin Rund3, and Rudolf Stollberger1 | ||
1Institute of Medical Engineering, Graz University of Technology, Graz, Austria, 2Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom, 3Institute for Mathematics and Scientific Computing, University of Graz, Graz, Austria |
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In this work, an optimal control framework and its application for the development and improvement of $$$B_1^+-$$$ and $$$\Delta B_0-$$$robust, slice-selective inversion pulses is introduced. The optimized RF pulse shows superior performance compared to adiabatic, state of the art pulses through simulations, phantom experiments, and in vivo measurements. Measurements on a 3T MR system revealed improved slice-profile quality of the optimized pulse, especially for low $$$B_1^+$$$ and high $$$\Delta B_0$$$. Since the performance is independent of the field strength, its application in ultrahigh-field spectroscopy seems straightforward. |
| 2867 | Computer 112
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Calibration of saturation prepared turbo FLASH B1+ maps by actual flip angle imaging at 7T. |
| Jan Sedlacik1,2,3,4, Raphael Tomi-Tricot1,2,3,5, Tom Wilkinson1,2,3, Pip Bridgen1,2,3, Franck Mauconduit6, Alexis Amadon6, Sharon Giles1,2,3, Joseph V Hajnal1,2,3, and Shaihan J Malik1,2,3 | ||
1Centre 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, 3London Collaborative Ultra high field System (LoCUS), London, United Kingdom, 4Radiology Department, Great Ormond Street Hospital for Children, London, United Kingdom, 5MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom, 6Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-yvette, France |
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A fast and accurate B1+mapping method is essential for making proper use of a parallel transmit array with high number of coil elements in a clinical setting. The saturation-prepared turbo FLASH method offers this capability and is implemented in the fully automated pre-scan adjustments of the currently only clinical ultra-high magnetic field strength MRI system. However, some parallel transmit methods require an even higher accuracy. This can be achieved by calibrating the fast B1+measurements with a more accurate but longer B1+mapping method. |
| 2868 | Computer 113
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Whole-liver flip angle shimming at 7T using eight-channel parallel transmission kt-points pulses with FPE-DREAM B1+ mapping |
| Bobby Runderkamp1, Wietske van der Zwaag2, Thomas Roos2, Gustav Strijkers3, Matthan Caan3, and Aart Nederveen1 | ||
1Radiology & Nuclear Medicine, Amsterdam UMC, Amsterdam, Netherlands, 2Spinoza Center for Neuroimaging, Amsterdam, Netherlands, 3Biomedical Engineering and Physics, Amsterdam UMC, Amsterdam, Netherlands |
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Liver MRI could benefit from the increased SNR at 7T but suffers from severe flip angle inhomogeneity. In this work, eight-channel parallel transmission is used for flip angle shimming, comparing circularly polarized transmission and phase shimming with a kt-points pulse. Fourier phase-encoded DREAM is used for artifact-free B1+ mapping. With kt-points, the nominal flip angle of 8˚ could be achieved with homogeneous signal over the entire liver, while phase shimming only delivers a flip angle of approximately 4˚ with less homogeneity. Future work is directed towards use of universal slab-selective kt-points pulses to make 7T liver MRI clinically feasible. |
| 2869 | Computer 114
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Inter-coil applicability of trained neural networks for B1+ prediction in parallel-transmit. |
| Alix Plumley1 and Emre Kopanoglu1 | ||
1Cardiff University, Cardiff, United Kingdom |
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Motion-resolved parallel-transmit (pTx) B1-maps can be predicted using neural networks, facilitating online pulse re-design – a prospective solution to motion. However, networks require large training-datasets. Since different pTx coils inherently produce different B1-distributions, it is unclear whether coil-specific training-datasets are needed. Here, we train networks on simulated data from one coil-model and test on 6 differently-sized coil-models. While performance was optimal for the coil on which networks were trained, B1-prediction yielded lower error than that caused by motion in ≥91% of magnitude, and ≥55% of phase evaluations for 5 out of the 6 models, demonstrating some generalisability across coils. |
| 2870 | Computer 115
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Head Position Related SAR Uncertainty Depends on Slice Orientation and Pulse Complexity |
| Emre Kopanoglu1 | ||
1CUBRIC / Psychology, Cardiff University, Cardiff, United Kingdom |
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Safety models on scanners are unaware of the actual patient position while excitation pulses are inherently position dependent. This study investigates the effect of this positional mismatch on SAR estimation for axial, coronal and sagittal slice orientations. The positional mismatch yields up to 5.2-fold underestimation of peak local SAR. RF shimming and 2-spoke parallel-transmit pulses for axial slice orientation have reduced SAR-sensitivity to positional mismatch with the worst-case underestimation being <2.0-fold whereas a reduced SAR-sensitivity was not observed for coronal and sagittal slices. For extreme head positions not represented in safety-models, axial RF shimming / 2-spokes parallel-transmit pulses maybe beneficial. |
| 2871 | Computer 116
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Motion-Dependent Low-Order Predictive Linear Model for Patient Safety Assessment at 7T with Technically Feasible Coil Models |
| Amer Ajanovic1,2, Yannick Brackenier1,2, Raphael Tomi-Tricot1,2, Joseph V Hajnal1,2,3, 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, 3Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom |
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Establishing a comprehensive model that addresses patient safety at UHF MRI with respect to motion is a non-trivial task because of the underlying computationally expensive frameworks. Using MARIE we computed a large number of pose simulations of 3 feasible coil models (birdcage, 4-channel and 8-channel pTx) in proximity to Duke body model to allow the parameter space to be well explored. It is found that a low order linear model can capture most of the variation in cpB1+. We also observe low variations in cpSAR for 2 realistic coil models across the conditions examined, with 8-channel coil being most robust. |
| 2872 | Computer 117
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Calibration-free parallel transmission for improved CSF mobility imaging at 7T |
| Philipp Ehses1, Lydiane Hirschler1,2, Eberhard Daniel Pracht1, Katerina Deike-Hofmann1, Vincent Gras3, Franck Mauconduit3, Aurélien Massire4, Nicolas Boulant3, Matthias J. P. van Osch2, and Tony Stoecker1,5 | ||
1German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, 2Radiology, Leiden University Medical Center, Leiden, Netherlands, 3University of Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif sur Yvette, France, 4Siemens Healthcare SAS, Saint-Denis, France, 5Department of Physics and Astronomy, University of Bonn, Bonn, Germany |
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Better understanding of how the brain cleans itself is of high importance as its failure has been linked to various neurodegenerative diseases. A first step towards elucidating CSF-mediated clearance mechanisms is the measurement of CSF motion in the human brain. In this work, we present an imaging sequence for CSF mobility measurements employing calibration-free parallel transmission. During the imaging session, no pulse calculations or complex B1 shimming procedures are necessary, making this approach feasible for large scale patient studies. |
| 2873 | Computer 118
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Respiration robust universal pulses in the human heart at 7T for shallow and deep breathing |
| Christoph Stefan Aigner1, Sebastian Dietrich1, Felix Krüger1, Max Lutz1, and Sebastian Schmitter1,2,3 | ||
1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany, 2German Cancer Research Center (DKFZ), Medical Physics in Radiology, Heidelberg, Germany, 3University of Minnesota, Center for Magnetic Resonance Research, Minneapolis, MN, United States |
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This study demonstrates the design and application of a new class of universal pulses (UP) designed for a library of 22 non-respiration resolved (NRR) B1+-maps acquired in-vivo during shallow breathing (SB) and 30 respiration resolved (RR) B1+-maps acquired during deep breathing (DB). The proposed UP was tested on 9 NRR SB (test-cases-SB) and 15 RR DB B1+-maps (test-cases-DB) and was applied experimentally in five volunteers (test-cases-DB) along with tailored pulses in multiple gradient echo measurements. Compared to tailored pulses, UP resulted in a slightly overall decrease of the FA homogeneity but similar image quality across all test-cases. |
| 2874 | Computer 119
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Eight Channel, Dual-Matrixed, Parallel Transmit RF Power Amplifier for 1.5T MRI |
| Thomas Vaughan1, Michael Garwood2, Steve Suddarth3, Lance DelaBarre2, and Dan Myer4 | ||
1BME, Radiology, Columbia University, New York, NY, United States, 2University of Minnesota, Minneapolis, MN, United States, 3University of Minneosta, Minneapolis, MN, United States, 4Communications Power Corp., Hauppauge, NY, United States |
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A new, laboratory grade RF power amplifier that offers eight channels of low, CW power for simultaneous transmit and receive applications, and eight channels of high, peak-pulsed power for conventional MRI is presented. These FPGA controlled, multiple transmit channels can be matrix switched into 1, 2, 4, and 8 channel combinations for a range of 2W, 4W, 8W and 16W CW, and 2kW, 4kW, 8kW and 16kW peak power pulses. Further each channel can be used for independent phase, gain, frequency, space and time for maximum flexibility in RF field modulation. This power amplifier meets our wide ranging experimental requirements. |
| 2807 | Computer 75
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Evaluation of the REFILL dynamic distortion correction method for fMRI |
| Simon Daniel Robinson1,2,3, Beata Bachrata3, Korbinian Eckstein3, Barbara Dymerska4, Saskia Bollmann2, Steffen Bollmann5, Shota Hodono2, Martijn Cloos2, Monique Tourell2, Jin Jin6, Kieran O'Brien6, David Reutens2, Siegfried Trattnig3, Christian Enzinger1, and Markus Barth5 | ||
1Department of Neurology, Medical University of Graz, Graz, Austria, 2Centre for Advanced Imaging, University of Queensland, Brisbane, Australia, 3Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, 4UCL Queen Square Institute of Neurology, University College London, London, United Kingdom, 5School of Electrical Engineering and Information Technology, University of Queensland, Brisbane, Australia, 6Siemens Healthineers, Brisbane, Australia |
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We evaluate the performance of a recently-proposed dynamic distortion correction (DDC) method for fMRI at 7T, with a task which generates field fluctuations. The Reverse-Encoded First Image and Low resoLution reference scan (REFILL) method generates fieldmaps from the phase of standard, single-echo EPI from fMRI time series, using coil sensitivity information from a fast reference scan and removing other, non-B0-related contributions to the phase, which are calculated from a readout-reverse EPI volume. In contrast to conventional static distortion correction (SDC) with a GE-based fieldmap, REFILL captured dynamic changes to the field, leading to an accurate correction and increased tSNR. |
| 2808 | Computer 76
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B0 shimming in human brain using rosette encoding at 7T |
| Jullie W Pan1, Chan H Moon2, and Hoby P Hetherington3,4 | ||
1Radiology, University of Missouri Columbia, Columbia, MO, United States, 2Radiology, University of Pittsburgh, Pittsburgh, PA, United States, 3Resonance Research Inc., Billerica, MA, United States, 4University of Missouri Columbia, Columbia, MO, United States |
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With increasing use of ultra-high field, there is a need for fast and efficient field mapping. Towards this purpose, the non-Cartesian circular rosette trajectory is advantageous due to its low gradient demands and its efficiency due to the simultaneous acquisition of spatial and field encoding information. We describe the implementation of the circular rosette trajectory for field mapping at 7T in the human brain and compare this to the highly accurate although slow 5 echo Bolero field map. |
| 2809 | Computer 77
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REconstruction of MR images acquired in highly inhOmogeneous fields using DEep Learning (REMODEL 2.0) |
| Marina Manso Jimeno1,2, John Thomas Vaughan Jr.1,2, and Sairam Geethanath2 | ||
1Department of Biomedical Engineering, Columbia University, New York, NY, United States, 2Columbia Magnetic Resonance Research Center, New York, NY, United States |
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The trade-off of a shorter MRI magnet design is having to compromise image quality due to reduced field homogeneity. Moreover, the sample induces unique field perturbations during the scan that can only be corrected if the exact field map is known. Here we proposed a DL model that synthesizes sample-specific field maps based on artifact-corrupted acquired images and the system’s field distribution. In the retrospective study, we obtained a mean NRMSE of 0.04 during testing between model output and the true field maps and found that using the model output for correction significantly reduced the artifacts on the images. |
| 2810 | Computer 78
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Towards gradient perturbation correction in diffusion weighted imaging based on the gradient system transfer function |
| Hannah Scholten1 and Herbert Köstler1 | ||
1Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany |
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Eddy current induced field perturbations can cause artifacts in diffusion weighted imaging (DWI). Such perturbations may be calculated and corrected for by the gradient system transfer function (GSTF), provided the gradient system behaves linear and time-invariant. We discovered that the linearity assumption can be violated by gradients with high zeroth order moments. We therefore propose a modified measurement scheme for the GSTF including higher gradient moments to better approximate their behavior. Our approach substantially reduces errors in the predicted gradient time courses. We may thus enable the application of GSTF-based correction methods to DWI in the future. |
| 2811 | Computer 79
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Reduced field of view CEST for high performance prostate imaging at 3T human scanner |
| Xubin Chai1,2, Chuyu Liu1, Chu Wang1, Rong Xue2, and Xiaolei Song1 | ||
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing, China, 2State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China |
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For imaging small-sized organs like the prostate, reduced-field-of-view (rFOV) technique is useful for shortening scan time, increasing resolution and reducing artifacts caused by field inhomogeneity and motion. Herein on a 3T clinical scanner, rFOV CEST was obtained using an off-resonance saturation preparation (seconds long), followed by readouts at the crossing section of a 90 deg excitation slab and a 180 deg refocus slab that had an angle in between. For saturation powers of 0.7 uT and 2 uT, CEST contrast maps and quantitative curves suggested the rFOV-CEST outperformed the Traditional-FOV acquisitions, which has potential for prostate CEST imaging at 3T. |
| 2812 | Computer 80
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Generalized Framework for Homogeneous Ultra-High-Field Brain Imaging |
| Patrick Liebig1, Juergen Herrler2, Raphael Tomi-Tricot3,4,5, Sydney Williams6, Belinda Ding-Yuan3,6, Majd Hlou7, Venkata Chebrolu8, Fasil Gadjimuradov7,9, Tom Hilbert10,11,12, Tobias Kober10,11,12, Rene Gumbrecht1, Robin Martin Heidemann1, Thomas Benkert7, Chris Rodgers13, David Andrew Porter6, Iulius Dragonu3, Armin Nagel14,15, and Shaihan Malik4,5 | ||
1Siemens Healthcare GmbH, Erlangen, Germany, 2Department of Neuroradiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany, 3MR Research Collaborations, Siemens Healthcare Limited, London, United Kingdom, 4Department of Biomedical Engineering, School of Biomedical Engineering and Imaging Sciences, King’s College London, St. Thomas’ Hospital, London, United Kingdom, 5Center for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King’s College London, St. Thomas’ Hospital, London, United Kingdom, 6Imaging Centre of Excellence, University of Glasgow, Glasgow, United Kingdom, 7MR Applications Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany, 8Siemens Medical Solutions USA, Inc., Rochester, MN, United States, 9Department of Computer Science, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany, 10Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland, 11Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland, 12LTS5, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, 13Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom, 14Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany, 15Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany |
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7T MRI is affected by inhomogeneous transmit and receive B1 field that can impede the inherent gains in signal-to-noise ratio. pTx provides excellent results in correcting the transmit field and showed feasibility in a clinical setting as well1,2. Although multiple algorithms have been developed to correct for the receive profile or signal homogeneities in general, each algorithm has its own shortcomings. Here, we suggest combining prospective correction of the transmit field by pTx with a deep learning network to retrospectively correct for the remaining signal inhomogeneities (mainly receive field variations) in a generalized fashion. |
| 2813 | Computer 81
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Safety of 4-channel parallel RF transmission MRI at 3 T: Effects of system uncertainty and system failure pertinent to deep brain stimulation |
| Benson Yang1,2, Chih-Hung Chen2, and Simon J Graham1,3 | ||
1Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada, 2Electrical and Computer Engineering, McMaster University, Hamilton, ON, Canada, 3Medical Biophysics, University of Toronto, Toronto, ON, Canada |
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Parallel radiofrequency transmission (pTx) technology continues to demonstrate its potential at addressing MRI safety concerns relating to patients with implanted deep brain stimulation devices. One promising technique involves electromagnetic simulation that determine optimized pTx inputs to generate a safe mode of imaging surrounding the implanted device. However, in practice, instrumentation uncertainty can impact the ability of the pTx system to accurately produce the desired signals. The present work studied the safety implications of system uncertainty and system failure in a 4-channel pTx platform. The preliminary results showed that in a worst-case scenario, temperature elevations that exceed MRI guidelines are possible. |
| 2814 | Computer 82
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Cardiac motion modeling using DENSE imaging to study cardiac diffusion tensor MRI |
| Kevin Moulin1,2, Tanjib Rahman 3, Magalie Viallon1,2, Pierre Croisille1,2, and Luigi Perotti3 | ||
1CREATIS, Lyon, France, 2Department of Radiology, University Hospital Saint-Etienne, Saint Etienne, France, 3Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL, United States |
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Cardiac Diffusion Tensor imaging (cDTI) is a powerful non-contrast technique that can characterize cellular structure in vivo. Despite motion-compensated diffusion encoding designs, cDTI remains sensitive to unwanted cardiac motion, particularly during diastole. The lack of knowledge of the detailed interaction between real cardiac motion and motion-compensated gradients prevents more advanced diffusion encoding designs. The objective of this work is to provide a new simulation framework to study the interaction between cardiac displacements estimated in vivo from DENSE imaging and motion-compensated diffusion encoding waveforms. |
| 2815 | Computer 83
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MRIsim.jl: A framework for end-to-end spin-level MRI simulations with GPU acceleration |
| Carlos Castillo-Passi1,2,3, Ronal Coronado2,3,4, Sergio Uribe2,3,5, and Pablo Irarrazaval1,2,3,4 | ||
1Institute of Biological and Medical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile, 2Biomedical Imaging Center, Pontificia Universidad Católica de Chile, Santiago, Chile, 3Millennium Nucleus in Cardiovascular Magnetic Resonance, Cardio MR, Santiago, Chile, 4Electrical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile, 5Radiology Department, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile |
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In this work, we proposed a GPU-enabled MRI simulation framework written in Julia. The primary purpose of this simulator is to evaluate imaging pipelines from the acquisition to the reconstruction. To showcase this, we simulated two variations of an MRF sequence with radial acquisitions and then reconstructed using two methods. We demonstrated that this framework aids users to quickly write and test state-of-the-art MRI techniques and showed its potential to compare imaging pipelines in quantitative mapping. |
| 2816 | Computer 84
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Image-based computer simulations of haemodynamics and blood cells distributions: A comparison between MRI and ultrasound |
| Vasit Sirilapanan1, Yongmann M Chung1, Richard Harrison2, Clare Cameron3, Michael Lynn4, Charles Hutchinson5, and Farhan Ahmed4 | ||
1School of Engineering, University of Warwick, Coventry, United Kingdom, 2School of Psychology and Clinical Language Sciences, University of Reading, Reading, United Kingdom, 3University of Herefordshire, Hatfield, United Kingdom, 4Department of Radiology, Royal Berkshire Hospital, Reading, United Kingdom, 5Medical School, University of Warwick, Coventry, United Kingdom |
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MRI-based CFD simulations are compared with ultrasound-based CFD to ascertain the capability of ultrasound. |
| 2924 | Computer 104
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OptiPulse: a flexible optimization framework for short water-selective radiofrequency pulse design |
| Xavier Sieber1,2, Jessica A. M. Bastiaansen1,2,3,4, Christopher W. Roy1,2, Jonas Richiardi1,2, Matthias Stuber1,2, and Ruud B. van Heeswijk1,2 | ||
1Department of Medical Radiology, Lausanne University Hospital (CHUV), Lausanne, Switzerland, 2University of Lausanne (UNIL), Lausanne, Switzerland, 3Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland, 4Translational Imaging Center, Sitem-insel, Bern, Switzerland |
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We present a flexible optimization framework to design spectral-selective radiofrequency pulses using numerical optimization on Bloch equation simulation. The RF pulse performance is assessed using a composite loss function for both fat suppression and power requirement. The framework was used to design three binomial (1-1, 1-2-1 and 1-3-3-1) and one cubic B-splines interpolated RF pulses. These pulses were then tested in vitro as well as in vivo in the knee and in the heart, where they demonstrated robust fat suppression comparable to a state-of-the-art water-selective pulse. |
| 2925 | Computer 105
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Pulse design for joint optimization of semisolid saturation and free water rotation |
| David Leitão1,2, Raphael Tomi-Tricot1,3, Pip Bridgen1, Tom Wilkinson1, Patrick Liebig4, Rene Gumbrecht4, Dieter Ritter4, Sharon Giles1, Ana Baburamani1, Joseph V. Hajnal1,5, and Shaihan J. Malik1,5 | ||
1Biomedical 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, 4Siemens Healthcare GmbH, Erlangen, Germany, 5Centre for the Developing Brain, King's College London, London, United Kingdom |
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In MT imaging, particularly at ultra-high field, results can be influenced by spatial variations in both (1) on-resonance flip angle and (2) RF saturation specified by B1rms including on- and off-resonance contributions. Conventional pulse design with parallel transmission focuses on homogenizing flip angle (α) distributions but does not explicitly account for B1rms distribution. In this work we propose a generalized pulse design framework that considers both α and B1rms and apply it to achieve uniform excitation and saturation at the same time. Performance is confirmed in phantom experiments at 7T, resulting in more uniform MTR compared to conventionally-designed pulses. |
| 2926 | Computer 106
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Design of Novel RF Pulse for Fetal MRI Refocusing Trains using Rank Factorization (SLfRank) to Reduce SAR and Improve Image Acquisition Efficiency |
| Sebastian Diaz1, Yamin Arefeen2, Borjan Gagoski3,4, Ellen Grant3,4, and Elfar Adalsteinsson2,5,6 | ||
1Department of Biomedical Engineering, University of Arizona, Tucson, AZ, United States, 2Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 3Department of Radiology, Harvard Medical School, Boston, MA, United States, 4Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Boston, MA, United States, 5Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, 6Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States |
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Fetal MRI is inherently time-constrained due to unpredictable motion and comfort concerns. Single-shot spin-echo sequences address these concerns by rapidly acquiring images with desired tissue contrast. However, these sequences typically operate at specific absorption rate (SAR) limitations due to a train of refocusing pulses, which impose long TR times and reduce acquisition efficiency. This study leverages SLfRank, the use of ranked factorization to jointly solve for SLR bi-coupled spin parameters, to design refocusing profiles that reduce SAR while maintaining slice-profile performance. The proposed refocusing pulse reduced SAR by over 20% while producing similar image quality to the standard clinical sequence. |
| 2927 | Computer 107
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Optimal control pulse design as a low power alternative to BIR4 excitation pulses |
| Vencel Somai1,2, Alan J Wright1, Ming Li Chia1, and Kevin M Brindle1,3 | ||
1CRUK CI, University of Cambridge, Cambridge, United Kingdom, 2Department of Radiology, University Of Cambridge, Cambridge, United Kingdom, 3Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom |
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The BIR4 pulse achieves adiabatic excitation over a moderate frequency range but has a relatively high adiabatic threshold, which is demanding on the hardware and deposits significant energy when the repetition rate is high. We show here using simulations and an experiment in vivo that optimal control can provide a better alternative with a significantly lowered adiabatic threshold. |
| 2928 | Computer 108
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Accelerated DeepRF using modified optimal control |
| Jiye Kim1, Dongmyung Shin1, Hongjun An1, Hwihun Jeong1, Minjun Kim1, and Jongho Lee1 | ||
1Department of Electrical and Computer Engineering, Seoul National University, Seoul, Korea, Republic of |
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DeepRF1 is a recently proposed RF pulse design method using deep reinforcement learning and optimization, generating RF defined by a reward (e.g., slice profile and energy constraint) from self-learning. Here, we proposed an accelerated algorithm for DeepRF that utilizes a modified optimal control, replacing the computationally complex gradient ascent-based optimizer. The new algorithm is tested for slice-selective inversion and slice-selective excitation and compared with original DeepRF and SLR RF pulses, reporting improved computation efficiency while preserving performances. Additionally, a short-duration B1-insensitive inversion pulse, which was difficult to produce in conventional RF algorithms, is designed to demonstrate the usefulness of DeepRF. |
| 2929 | Computer 109
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Extension of k-space formalism with refocusing RF pulses |
| Zungho Zun1 and Taehoon Shin2,3,4 | ||
1Weill Cornell Medicine, New York, NY, United States, 2Division of Mechanical and Biomedical Engineering, Ewha Womans University, Seoul, Korea, Republic of, 3Graduate Program in Smart Factory, Ewha Womans University, Seoul, Korea, Republic of, 4Department of Medicine, Case Western Reserve University, Cleveland, OH, United States |
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Conventional k-space analysis of excitation based on Fourier relationship between excitation profile and RF deposit in k-space is extremely useful for pulse sequence design but is strictly limited to the small-tip-angle regime. We propose a new theoretical viewpoint for including refocusing pulses in the k-space formalism and demonstrate that the effect of refocusing pulse can be viewed as origin symmetric rotation of RF deposit in k-space. This new viewpoint may enable analytic approaches to designing RF pulses with multiple refocusing pulses and offer new opportunities to develop complex RF pulses that require insensitivity to off-resonance. |
| 2930 | Computer 110
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Making Reduced FOV Imaging Applicable on Low-Cost MRI Systems: A Sheared 2DRF Excitation Approach |
| Bahadir Alp Barlas1,2 and Emine Ulku Saritas1,2,3 | ||
1Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, 2National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey, 3Neuroscience Graduate Program, Bilkent University, Ankara, Turkey |
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The utilization of low-cost low-field MRI systems has been rising due to the recent image quality improvements. However, these systems cannot incorporate numerous popular MRI techniques due to their hardware limitations. This work proposes a sheared 2DRF pulse design to make reduced FOV imaging applicable for low-cost MRI systems. The proposed sheared 2DRF pulse design provides significant reduction in pulse duration together with improved signal under B0 field inhomogeneities, while ensuring robust sidelobe suppression and unlimited slice coverage. We demonstrate the proof-of-concept applicability of the proposed approach for a 0.35T and a 1.5T MRI scanner. |
| 2931 | Computer 111
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Simultaneous Multi Slice using Hadamard like encoding with non-Hadamard factors |
| Sudhir Ramanna1, Harsh Agarwal1, Rajagopalan Sundaresan1, Sajith Rajamani1, Ashokkumar P Reddy1, Bhairav Mehta1, and Ramesh Venkatesan1 | ||
1GE Healthcare, Bangalore, India |
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Multiplexing of slices using the NEX/averaging dimension is an option for clinical MR protocols to improve SNR without imposing a scan time penalty. Hadamard encoding and decoding imposes Hadamard factors as limits where in only powers of 2 is used. We propose to use a Hadamard like encoding scheme but decode differently to yield a reduced effective NEX and improved motion sensitivity. This enables us to use any integer multiband factors. |
| 2932 | Computer 112
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Investigating a residual neural network to generated customizable RF pulses for MRI |
| Seger Nelson1 and Rebecca Emily Feldman2,3 | ||
1Computer Science, Mathematics, Physics, and Statistics, University of British Columbia, Kelowna, BC, Canada, 2Computer Science, Mathematics, Physics, and Statistics, University of British Columbia Okanagan, Kelowna, BC, Canada, 3Biomedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States |
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We investigate a method for the design of radio frequency (RF) pulses for custom simultaneous multi slice spatial profiles. We trained a variation of residual neural networks on a dataset of 96,000 generated adiabatic “power independent of the number of slices” (PINS) RF pulses, varying parameters such as gradient duty cycle, number of pulse lobes, quadratic phase strength, and transition and filter bandwidth. We compared the direct-design RF pulses to those generated by our model. |
| 2933 | Computer 113
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B1-Compensating RF Excitation for Imaging hyperpolarized 13C nuclei with bSSFP using a 13C Cryo-Coil |
| Luca Nagel1, Geoffrey J. Topping1, and Franz Schilling1 | ||
1Department of Nuclear Medicine, TUM School of Medicine, Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany |
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Cryogenically cooled transmit/receive RF surface coils (cryocoils) can improve signal-to-noise ratio (SNR) up to 4X1. With flat profile RF pulses, surface coil excitation profiles are highly inhomogeneous, complicating the use of most pulse sequences, and especially the fast and efficient bSSFP sequence. A transmit B1-compensating RF pulse that produces uniform excitation with a Tx/Rx 13C cryo-coil was developed and tested in 3D-FLASH and 3D-bSSFP. Thermal 13C phantom imaging showed a regional uniform excitation, and proof-of-concept time-resolved 3D bSSFP imaging of hyperpolarized [13C]urea was demonstrated in mice. |
| 2934 | Computer 114
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Simultaneous Multislice Imaging Using Multiphoton MRI |
| Tanya Deniz Ipek1, Victor Han1, Jingjia Chen1, and Chunlei Liu1,2 | ||
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States, 2Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States |
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Simultaneous multislice (SMS) imaging accelerates data acquisition by exciting several slices simultaneously but has a higher specific absorption rate (SAR) due to additional radiofrequency (RF) pulses required to excite multiple frequencies. Multiphoton excitation achieved by oscillating gradient fields provides frequency sidebands, eliminating the need for additional excitation pulses. We have demonstrated SMS imaging for multiphoton MRI and used SENSE reconstruction to separate simultaneously acquired slices with the help of coil sensitivity profiles. Multiphoton SMS images achieve a similar quality to standard one-photon SMS images but offer the benefit of reduced SAR as they do not require extra RF power. |
| 2935 | Computer 115
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Frequency-selective pTx pulses for 3D echo planar imaging at ultra-high field |
| Arun Joseph1,2,3, Patrick Liebig4, Gabriele Bonanno1,2,3, Jin Jin5,6, Kurt Majewski7, Tobias Kober8,9,10, and Tom Hilbert8,9,10 | ||
1Advanced Clinical Imaging Technology, Siemens Healthcare AG, Bern, Switzerland, 2Translational Imaging Center, sitem-insel AG, Bern, Switzerland, 3Magnetic Resonance Methodology, Institute of Diagnostic and Interventional Neuroradiology, University of Bern, Bern, Switzerland, 4Siemens Healthcare GmbH, Erlangen, Germany, 5Siemens Healthcare Pty Ltd, Brisbane, Australia, 6ARC Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, Brisbane, Australia, 7Siemens AG, Munich, Germany, 8Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland, 9Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland, 10LTS5, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland |
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Echo planar imaging is an important MR technique used for different applications in both structural and functional imaging. It is typically used with fat suppression to avoid phase inconsistencies induced by the chemical shift of the fat signal. pTx pulses are used to mitigate the B1+ bias field occurring at higher fields strengths; typical pTx pulses do however not suppress the fat signal. In this work, we designed a frequency-selective water excitation pTx pulse to be used in 3D EPI acquisitions, enabling homogenous, high-resolution whole-brain fat-free imaging at 7T. |
| 2936 | Computer 116
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Velocity selective arterial spin labelling using parallel transmission |
| Chia-Yin Wu1,2,3, Jin Jin2,4, Carl Dixon1, Donald Maillet1, Markus Barth1,2,3, and Martijn Cloos1,2 | ||
1Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia, 2ARC Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, Brisbane, Australia, 3School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia, 4Siemens Healthcare Pty Ltd, Brisbane, Australia |
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In this work, we demonstrate a parallel transmit implementation of velocity selective arterial spin labelling (VSASL) at 7 Tesla on a custom flow phantom developed in house. The use of tailored pTx pulses can greatly mitigate the transmit field inhomogeneities present at higher field strengths. By manipulating the time symmetry of the pTx pulses in the VSASL module we were able to show significant improvement in velocity selective inversion fidelity. |