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Digital Poster - Engineering/Interventional/Safety Weekend and Oral

Digital Poster (no CME credit)

SMRT Ed Session

SMRT Poster Presentations (no CME credit)

Acq/Recon/Analysis Digital Poster	Body Digital Poster	Cancer/Spectroscopy/Molecular Imaging/Pre-Clinical Digital Poster	Cardiovascular Digital Poster
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MR Value Digital Poster	Musculoskeletal Digital Poster	Neuro Digital Poster	Pediatrics Digital Poster

Engineering/Interventional/Safety Digital Poster (No CME Credit)

Parent Session Title

RF Design I

Program # 1391 - 1430

RF Design II

Program # 1571 - 1610

Safety

Program # 2279 - 2317

Safety & Multinuclear/Preclinical RF

Program # 2477 - 2516

Systems Engineering I

Program # 3085 - 3124

Systems Engineering II

Program # 3325 - 3364

Interventional & Low-Field MRI

Program # 4005 - 4044

Interventional, Multimodal & Auxiliary Engineering

Program # 4242 - 4281

Developments in RF Components

RF Design I

Engineering/Interventional/Safety

1391		The Coax Dipole Antenna: a flexible, low SAR dipole antenna for body imaging at 7 Tesla.
		Carel C. van Leeuwen¹, Bart R.E. Steensma¹, Dennis W.J. Klomp¹, Cornelis A.T. van den Berg¹, and Alexander J.E. Raaijmakers^1,2
		¹University Medical Center Utrecht, Utrecht, Netherlands, ²Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
		A coax cable dipole antenna with gaps in the shield supports flat current profiles on the outside of the shield. A simulation study is performed to further optimize the design of this flexible so-called ‘coax dipole antenna’. MR thermometry measurements are performed using a single antenna and a homogeneous phantom. The coax dipole antenna causes 18% lower peak heating than a fractionated dipole antenna. An array of eight coax dipole antennas is used to generate T2-weighted images and B1 maps of the prostate of three volunteers, where the coax dipoles achieve the same B1 as an array of fractionated dipoles.

1392		Bailey splitter/combiner for RF shimming/Rx coil combination
		Yue Zhu^1,2, John C Gore^1,2,3,4, and Xinqiang Yan^1,2
		¹Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, ³Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ⁴Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, United States
		We designed a continuously adjustable Bailey splitter/combiner with a sliding mechanism. This device has a good input matching of < -18dB and a low insertion loss of about -0.5dB. The sliding mechanism allowed easy handling and precise adjustments. The resistor free design eliminated the potential safety concern from the previous Ratio Adjustable Power Splitter circuits. We obtained good agreements between predicted and measured transmit field maps with the Bailey splitter/combiner.

1393		Performance of flexible coaxial transmission line resonator coils vs. stranded wire coils at 3 T
		Raphaela Czerny¹, Michael Obermann¹, and Elmar Laistler¹
		¹High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
		As flexible form-fitting RF coils can provide enhanced receive sensitivity in MRI, various coil design approaches have been studied recently, including coaxial and stranded wire coil elements. While stranded wire coils are electrically identical to conventional rigid copper loop coils, coaxial transmission line resonators are self-resonant and do not require additional components along the conductor. The goal of this work was to compare flexible receive-only stranded wire coils and coaxial coils in terms of Q-factors, inter-element coupling, noise correlation, and SNR.

1394		High Impedance Loop coil Design for improved EM Decoupling in Multichannel Coil arrays
		Sirihaas Gaddipati¹ and Xiaoliang zhang²
		¹University at Buffalo, Buffalo, NY, United States, ²Biomedical Engineering, University at Buffalo, Buffalo, NY, United States
		In traditional magnetic resonance imaging (MRI) design, ideal coil overlapping is used to minimize coupling between nearest-neighbor coils, and low input impedance preamplifiers are used to isolate the relatively weak coupling. Modern-day MR systems use phased array coils constructed out of low impedance resonant loops. Inside such arrays, electrodynamic interactions between elements must be carefully balanced[1]. However, to make the complex sensitivities of phased-array coils sufficiently distinct in parallel spatially-encoded MRI, needed an overlapping between coils. This electromechanical balancing act becomes increasingly difficult as the number of receive elements grows for optimal performance, leading to geometrical puzzles of profound complexity.

1395		An Improved Power Handling Active Transmit/Receive Switch for Low Field MRI using Reed Relays
		Don Straney¹, Clarissa Zimmerman Cooley^1,2, and Matthew S Rosen^1,2,3
		¹Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Department of Physics, Harvard University, Cambridge, MA, United States
		An active transmit/receive (T/R) switch based on reed relays shows promise in overcoming the previous limitations at low field of both passive and active T/R switches. We aim to provide a design for other low-field researchers to use which handles a wide range of frequencies (DC to 3.4 Mhz) and power levels (<1 mW to 2 kW pulsed) in a simple, low-parts-count device which is easy to reproduce.

1396		Use of High - Permittivity Pads to enhance SNR and Transmit Efficiency in the Chest at 7T
		Giuseppe Carluccio^1,2 and Christopher Michael Collins^1,3
		¹Radiology, Center for Advanced Imaging Innovation and Research (CAI2R), New York, NY, United States, ²Radiology, Bernard and Irene Schwartz Center for Biomedical Imaging, New York, NY, United States, ³Bernard and Irene Schwartz Center for Biomedical Imaging, New York, NY, United States
		High-Permittivity materials have been recently used to shape the B1 field distribution to enhance SNR and transmit efficiency. So far, these materials have been mainly applied to increase SNR in the head. In this work, through numerical simulations, we explore the possibility to use high-permittivity pads to improve the signal in the chest. The pads are positioned between the model of the coils (8 TEM transmit coils and 24 receive loops) and of the human body. Our simulations show that some improvement can be obtained by adding the pads to the coils.

1397		Introducing the Double-Folded Dipole to enhance the Excitation Efficiency at 7T Ultra-High Field MRI
		Sam-Luca J.D. Hansen¹, Markus W. May¹, Mirsad Mahmutovic¹, Manisha Shrestha¹, Anpreet Ghotra¹, Matthäus Poniatowski¹, and Boris Keil¹
		¹Institute of Medical Physics and Radiation Protection, TH Mittelhessen University of Applied Sciences, Gießen, Germany
		We demonstrated a highly efficient B₁⁺to-SAR dipole antenna for ultrahigh-field MRI which consists of a double-folded ladder structure. The antenna was simulated and bench tested. The antenna has a high impedance which provides low mutual coupling between other antenna elements. Ultimately, this characteristic possibly allows to construct antenna array for pTx.

1398		Non-Uniform Dielectric Substrate (NODES) Antenna Design for Cardiac Imaging at 7T
		Alireza Sadeghi-Tarakameh¹, Bahram Khalichi², Xiaoping Wu¹, Gregory J. Metzger¹, and Yigitcan Eryaman³
		¹Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, MN, United States, ²Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, ³University of Minnesota, Minneapolis, MN, United States
		Utilizing receive and transmit array coils with improved SNR/SAR performance is crucial to realizing the full potential of ultra-high field (UHF) MRI. In this work, we optimize a previously introduced antenna (NODES) to improve its SNR and SAR performances for 7T cardiac MRI applications.

1399		Parametric Coil Optimization via Global Optimization
		Jose EC Serralles¹, Elfar Adalsteinsson^2,3, Lawrence L Wald⁴, and Luca Daniel¹
		¹Computational Prototyping Group (CPG), Research Laboratory of Electronics (RLE), Department of Electrical Engineering and Computer Science (EECS), Massachusetts Institute of Technology (MIT), Cambridge, MA, United States, ²Department of Electrical Engineering and Computer Science (EECS), Massachusetts Institute of Technology (MIT), Cambridge, MA, United States, ³Institute for Medical Engineering and Science (IMES), Massachusetts Institute of Technology (MIT), Cambridge, MA, United States, ⁴Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
		Algorithmic design of coil arrays in MRI is typically considered desirable but computationally intractable. In this work, we demonstrate that it is in fact feasible to programmatically optimize over the design of a coil array to achieve a metric-of-interest, such as slice homogeneity in the transmit field. We build on previous work by employing global optimizers in several of the key steps in the optimization procedure. We demonstrate the effectiveness of this approach via a couple of numerical examples.

1400		MR imaging with a standard electro-optical modulator: Initial results
		Paul Nobre¹, Gwenaël Gaborit^2,3, Raphaël Sablong¹, 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
		The large majority of receiver clinical MR coil are using cables between the resonant coil and Connector plug. To remove possible induced currents on the cable’s shield, circuits such as RF traps are distributed along the cable. This is done to ensure patients’ safety during the exam. RF-traps are difficult to miniaturize and are not fit for inner coils such as endoluminal coils. Optical fibers would be a smart option to get rid of this critical drawback but this requires electro-optical conversion devices. This abstract presents the first images obtained at 7T with an electro-optical conversion based on Pockel’s effect.

1401		Correcting meander-line surface coil fields for large-area near-surface imaging
		Gary Zabow¹, Stephen Dodd², and Alan Koretsky²
		¹Applied Physics Division, National Institute of Standards and Technology (NIST), Boulder, CO, United States, ²NINDS, National Institutes of Health (NIH), Bethesda, MD, United States
		Planar meander-line coils have been proposed as ideal surface coils because they should, theoretically, create highly uniform fields over planes of essentially unlimited area. Experimentally, however, field uniformity of planar meander-line coils is often worse, not better, than even simple loop surface coils. This presentation shows why existing predictions of meander-line coil fields and imaging performance are misinterpreted and how coil geometries can be simply corrected to better match theory. In particular, it is shown how a single extra turn of wire can increase field uniformity by at least an order of magnitude, allowing for uniform, large-area near-surface imaging.

1402		UVC Based Wireless Patient Bore Disinfection Utilizing Scanner RF Transmission
		Devavrat Likhite¹, Rob Amerling¹, Leon Lee¹, and Saban Kurucay¹
		¹GE Healthcare, Waukesha, WI, United States
		In the recent times, cleaning protocols after every patient, regular disinfection of medical equipment and use of single-use devices have become a common practice. MRI equipment has been one of the most difficult imaging modalities to clean. Here, we present a simple technique that uses UV light to disinfect the MRI system, without the use of any external power or connecting cables. This technique uses the power from the MRI system and thereby provides a simple and wire-free UV disinfection solution that does not need external electrical source.

1403		Smart Metamaterials for 3T MRI
		Dennis Philipp¹, Endri Stoja², Simon Konstandin¹, Robin Wilke¹, Diego Betancourt², Thomas Bertuch², Juergen Jenne^1,3, Reiner Umathum^1,3, and Matthias Guenther^1,4
		¹Fraunhofer MEVIS, Bremen, Germany, ²Fraunhofer FHR, Wachtberg, Germany, ³German Cancer Research Center DKFZ, Heidelberg, Germany, ⁴MR Imaging and Spectroscopy, Faculty 01, University of Bremen, Bremen, Germany
		Smart metasurfaces, special two-dimensional metamaterial devices, have a huge potential to drastically improve imaging efficiency in MRI and are a promising tool to overcome some of the limitations which are hampering technological advances in the field. The design, simulation, and experimental verification of thin, smart, non-linear metasurfaces is presented, which yield an up to eightfold enhanced signal-to-noise ratio in 3T MRI. The smart metasurface is a system of two inductively coupled structures, one of which has a non-linear, incident power-dependent behavior. On-bench characterization and MRI scans with a homogeneous phantom and a kiwi fruit prove the functionality and working principle.

1404		High dielectric sheet to reduce electric fields in Self-decoupled radiofrequency coils for magnetic resonance imaging
		Aditya Ashok Bhosale¹ and Xiaoliang Zhang¹
		¹Biomedical Engineering, State University of New York, Buffalo, Buffalo, NY, United States
		Self-decoupled radiofrequency coils reduce the electromagnetic coupling between the coil elements and eliminate the use of complex decoupling technologies. The use of a small value capacitor (Cmode) in a self-decoupled coil helps in eliminating the coupling between coil elements but causes a large electric field across the Cmode capacitor1.which may potentially cause a safety problem during imaging. In this study, we propose the use of a high dielectric sheet to reduce the electric field across the capacitor and thereby reducing the higher SAR in the subject.

1405		Lightweight metasurface pads for passive RF shimming in 3T abdominal imaging
		Tania del Socorro Vergara Gomez^1,2, Marc Dubois^1,2,3, Pierre Jomin², Megdouda Benamara³, Djamel Berrahou³, Elodie Georget³, Tryfon Antonakakis³, David Bendahan¹, 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
		Abdominal imaging at 3T suffers from B₁⁺ inhomogeneities due to radiofrequency (RF) wavelength reduction. High permittivity dielectric pads have been introduced as suitable solution to this problem. Such pads can require up to a few kilograms of ceramic powder usually dispersed in water. This could be detrimental to patient comfort during examination. Here we present a new approach based on thin, lightweight and flexible metasurface pads. The pads are shown to improve transmit and receive efficiency together with SNR in vitro.

1406		Passive Tunable RF Leakage Canceller for Simultaneous Transmit and Receive (STAR) RF Coils at 1.5T Imaging
		Zachary Colwell¹, Djaudat Idiyatullin², Lance DelaBarre², Thomas Vaughan³, Michael Garwood², and Sung-Min Sohn¹
		¹School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States, ²Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, ³Zuckerman Institute, Columbia University, New York, NY, United States
		Simultaneous Transmit and Receive (STAR) requires high decoupling between the RF transmitter and receiver. Current methods for this include, but are not limited to: geometric isolation, active RF leakage cancellation and metamaterial decoupling. The presented method uses a passive, four-port, tunable canceller circuit to achieve upwards of 40 dB of isolation between a quadrature transmit coil pair and the single receiving coil for a 1.5T system.

1407		Gallium nitride MOSFETs enable transmit-receive switching in less than 100ns
		Christoph Michael Schildknecht¹, Markus Weiger¹, Romain Froidevaux¹, and Klaas Paul Pruessmann¹
		¹Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zürich, Switzerland
		For short-T2 MRI measurements, fast T/R switches that can handle high RF power are of paramount importance. In this work, we present a T/R switch based on GaN MOSFETs that switches in tens of nanoseconds and can handle a peak power of more than 1000W.

1408		Galvanically Isolated RF Switches for Low Field MRI
		Mike Twieg¹
		¹Hyperfine Research, Guilford, CT, United States
		RF switches occupy many roles in MRI RF systems, including spoiling, damping, transmit/receive (T/R) switches, digital tuners, and crossbar switches. For high field MRI, PIN diodes are the switching device of choice, but at low field strength FETs are attractive. However, implementing the typical drive circuitry for the switch is difficult at lower frequencies. Here we describe a novel drive circuit suitable for a broad frequency range. It does not rely on any ferrous materials, or any high frequency oscillating circuits, and is thus suitable for use on the coil.

1409		UWB antenna system fidelity investigation for wireless MRI
		Wonje Lee¹, Fraser Robb², John Pauly³, Shreyas Vasanawala¹, and Greig Scott³
		¹Pediatric Radiology, Stanford University, Palo Alto, CA, United States, ²GE Healthcare, Aurora, OH, United States, ³Electrical Engineering, Stanford University, Palo Alto, CA, United States
		We assess the effect of UWB antenna arrangement within a simulated bore environment that includes a pediatric human phantom using system fidelity factor calculations for wireless data link integrity

1410		Flexible Tunable Capacitor: A Variable Capacitor for Tuning Flexible/Thermoformed MRI Coils
		Julian Adolfo Maravilla¹, Karthik Gopalan¹, Ana Claudia Arias¹, and Michael Lustig¹
		¹EECS, UC Berkeley, Berkeley, CA, United States
		Recent advances in coil design and fabrication have allowed for flexible and thermoformed coil arrays. However, the weak solder joints and rigid design of traditional variable capacitors used with these coils greatly limit their flexibility. Here, we propose the Flexible Tunable Capacitor (FTC), a high-Q, flexible, easily tunable variable capacitor. This design uses an array of small low-loss parallel plate capacitors adjustable with small step sizes by exploiting series and parallel combinations. This work proposes a basic design that offers a wide range of capacitor values (0.5 pF to 7 pF) suitable for 3T and 7T coils.

Novel RF Coils & Components

RF Design I

Engineering/Interventional/Safety

1411		Rapid high power transmit-receive switching using a timed cascade of PIN diodes
		Christoph Michael Schildknecht¹, Markus Weiger¹, Romain Froidevaux¹, and Klaas Paul Pruessmann¹
		¹Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zürich, Switzerland
		For imaging of short-T2 samples often very short excitation pulses are desired, which requires high peak RF power. In this work, a transmit-receive switch is presented that can handle 18kW peak RF power and switches its state in less than 1µs. The novel design uses a timed cascade of anti-parallel PIN diode pairs to achieve this performance.

1412		Analysis of preamplifier decoupling effect in MRI coil array with electromagnetic field and RF circuit co-simulation
		Ming lu^1,2, Bei Zhang³, John C. Gore^1,2, and Xinqiang Yan^1,2
		¹Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, ³Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States
		Preamplifier decoupling is a standard way of suppressing inter-element inductive coupling in MRI receive arrays. A well-known method to evaluate and optimize RF coils before practical fabrication is to use circuit-level and electromagnetic (EM) field-level simulations. However, to be best of our knowledge, currently there is not a solid method to evaluate the preamp decoupling effect with circuitry and EM field analysis. In this work, we used RF circuit and EM co-simulation4 to evaluate the preamplifier decoupling effect and tested it on the conventional coil (LIC) and the recently introduced high impedance coil (HIC).

1413		Should coaxial coils be operated at their self-resonance? A simulation study
		Sigrun Roat¹, Andre Kuehne², Lena Nohava^1,3, and Elmar Laistler¹
		¹High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²MRI.TOOLS GmbH, Berlin, Germany, ³CEA, CNRS, Inserm, BioMaps (Laboratoire d'Imagerie Biomédicale Multimodale Paris Saclay), Université Paris-Saclay, Orsay, France
		Flexible RF coils gained large interest in recent years. One possibility to achieve flexibility is using transmission line resonator-type coils made from coaxial cable. These self-resonant structures can be constructed without lumped elements along the loop enhancing flexibility. No consensus has been reached yet whether these coils should be driven at their respective self-resonance. To investigate this question, we have performed a simulation study investigating 11 different setups at 3 frequencies each

1414		Conformal design of radio-frequency head coil for ultra-high field MRI
		Tiago Martins¹, Tales Santini¹, Jacob Berardinelli¹, Anthony DeFranco¹, and Tamer S Ibrahim¹
		¹University of Pittsburgh, Pittsburgh, PA, United States
		In this work, we explore a conformal Tic Tac Toe (TTT) head coil design for ultra-high field MRI. By conforming the antennas to the human head, we can extract better homogeneity allowing for better radiofrequency shimming. The comparison between the traditional TTT design and the conformal TTT design shows expanded coverage, reduction of the coefficient of variation by 0.4% and same intensity for the 16-channel version. The conformal designs are extremely flexible as its advantages can be explored for different configurations and sizes.

1415		Safety and imaging performance of 2-channel RF shimming for fetal MRI at 3T
		Filiz Yetisir¹, Esra Abaci Turk^1,2, P. Ellen Grant^1,2,3, Elfar Adalsteinsson^4,5, and Lawrence L. Wald^3,5,6
		¹Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Boston, MA, United States, ²Department of Pediatrics, Harvard Medical School, Boston, MA, United States, ³Department of Radiology, Harvard Medical School, Boston, MA, United States, ⁴Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, ⁵Harvard-MIT Division of Health Science and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, ⁶Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States
		3T MRI provides increased SNR but poses technical challenges for fetal imaging such as increased field inhomogeneity and SAR. RF shimming can address some of these challenges but also adds safety considerations. Using a diverse set of 5 numerical pregnant body models generated from patient MRI datasets, we found that 2-channel RF shimming can improve transmit field amplitude and uniformity by up to 19% and 36% respectively without increasing maternal or fetal SAR. The biggest difference in SAR and transmit field patterns was observed between the supine models and the left lateral model.

1416		Stabilization of bias field on 3D MPRAGE at 7T with dielectric pads and 3D-based B1+ scaling
		Giske Opheim¹, Vincent O. Boer², Esben Thade Petersen^2,3, Martin Prener¹, Olaf B. Paulson^1,4, and Jan Ole Pedersen⁵
		¹Neurobiology Research Unit, Dept. of Neurology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark, ²Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Hvidovre, Denmark, ³Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kgs. Lyngby, Denmark, ⁴Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark, ⁵Philips Healhtcare, Copenhagen, Denmark
		7T MRI has several cases of demonstrated clinical yield, but is challenged by spatial B₁ inhomogeneity. Bias fields in structural images may be acceptable for visual and computational analysis, and can to some extent be accounted for by bias-field corrections. However, this is significantly complicated since the characteristics of the bias field often varies between patients. By analyzing stability of bias fields in 3D MPRAGE images, we compared two dielectric pad setups and the impact of 3D-based B₁⁺ scaling, i.e., optimization of the RF gain. We found increased stability by using large pads and 3D-based B₁⁺ scaling in combination.

1417		The impact of B1+ on the optimisation of high-resolution ASL acquisitions at 7T
		Sriranga Kashyap¹, Roy A. M. Haast², Thomas F. Kirk³, An T. Vu^4,5, Denizhan Kurban¹, Ron Hellenbrand¹, Christopher J. Wiggins⁶, Alard Roebroeck¹, Ali R. Khan², David A. Feinberg^1,7,8, Benedikt A. Poser¹, and Dimo Ivanov¹
		¹Department of Cognitive Neuroscience, Maastricht University, Maastricht, Netherlands, ²Centre for Functional and Metabolic Mapping, Western University, London, ON, Canada, ³University of Oxford, Oxford, United Kingdom, ⁴University of California, San Francisco, CA, United States, ⁵San Francisco Veteran Affairs Health Care System, San Francisco, CA, United States, ⁶Scannexus B.V., Maastricht, Netherlands, ⁷Advanced MRI Technologies, Sebastopol, CA, United States, ⁸Helen Wills Neuroscience Institute, University of California, Berkeley, CA, United States
		In this 7T study, we examined potential causes of apparent absence of perfusion in the right inferior temporal lobe, by (i) assessing the B₁⁺ distributions on two 1Tx/32Rx head-coils to rule out a hardware source, and (ii) optimising the spatial positioning of dielectric pads to achieve a more symmetric B₁⁺ field. We observed that using an optimised dielectric pad positioning allows for a near whole-brain symmetric B₁⁺, thereby, ensuring the adiabatic condition for the inversion pulse is fulfilled, resulting in the robust measurement of perfusion in the right temporal lobes.

1418		Is it feasible to Make More Effective Use of Finite RF Power Resources in pTx Systems Using a Coupling Matrix?
		Stephen E. Ogier¹, Shaihan Malik¹, and Joseph Hajnal^1,2
		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
		Parallel transmit using equal numbers of RF power amplifiers and coil elements has emerged as a common way to improve the homogeneity of the transmit field through RF shimming. When performing RF shimming, in many cases the magnitude of the transmit field is limited by the maximum power limit of a single RF amplifier. We propose networks that can be used to share power between transmit channels, increasing the maximum transmit field. These networks are shown to provide substantial flexibility in RF power allocation for certain conditions on the relative phases of the channels.

1419		Design of transmit array coils by minimizing the modal reflected power values and increasing B1+ efficiency
		Ehsan Kazemivalipour^1,2, Giorgio Bonmassar³, Laleh Golestanirad^4,5, and Ergin Atalar^1,2
		¹Electrical and Electronics Engineering Department, Bilkent University, Ankara, Turkey, ²National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey, ³AA. Martinos Center, Massachusetts General Hospital (MGH), Harvard Medical School, Boston, MA, United States, ⁴Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States, ⁵Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States
		The vast majority of RF coil design techniques are based on reducing the coupling level to increase the coils' power efficiency. The assessment of scattering (S) parameters plays a crucial role in these techniques. However, just by checking S-parameters, we cannot be sure that the coil's accepted power generates a field with useful characteristics. Here, we propose to perform the co-simulation on transmit array coils and replace unknown capacitors with power sources. Extraction of the field profiles of the coil's lumped ports/elements could provide the opportunity to involve the field-dependent parameters in the minimization procedure of finding the coil's capacitors.

1420		Brain perfusion imaging using pseudo-continuous arterial spin labelling MRI: impact of RF coil shimming of the labelling region
		Sofia Guterres¹, Ana Rodrigues Fouto¹, Nuno André Silva², Pedro Vilela³, and Patrícia Figueiredo¹
		¹Institute for Systems and Robotics - Lisboa and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal, ²Hospital da Luz Learning Health, Lisboa, Portugal, ³Hospital da Luz, Lisboa, Portugal
		The labelling efficiency of pCASL perfusion imaging sequences can be hampered by B0 field inhomogeneities. We assessed the impact of shimming the labelling region using a commercial RF coil with dedicated shiming channels in the neck, on data acquired from healthy volunteers. Brain perfusion was quantified, as well as the labelling efficiency (based on B0 fieldmaps and numerical simulations). Simulation experiments show that labelling efficiency significantly depends on B0 field inhomogeneity. In vivo experiments, however, showed subtle inhomogeneity reduction within the arteries in the labelling region, yielding no significant improvements in pCASL labelling efficiency or the respective perfusion signal.

1421		The Impact of Quasi-Transverse Electric Modes Excited by Dipole Antennas on Transmit Field in In Vivo Ultrahigh Field MRI
		Daniel Wenz^1,2 and Rolf Gruetter^1,3
		¹CIBM Center for Biomedical Imaging, Lausanne, Switzerland, ²Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland, ³Laboratory of Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
		This work investigates quasi-transverse electric modes which can be excited within rectangular dielectric blocks which are often used to shorten dipole antennas for MRI at 7T. In simulations we studied different parameters which can affect the performance of a dielectrically-shortened dipole antenna. We showed that an optimal geometry for the case when the block and the sample are physically separated differs significantly from the case when perfect direct contact is achieved. Two prototypes were built and used in an in vivo MRI experiments involving one subject showing how different dielectric modes can affect the image quality.

1422		A Novel High Density 32-channel Sleeve Antenna Receiver Array for the Human Head Imaging at 10.5 T
		Myung Kyun Woo¹, Lance DelaBarre¹, Matt Waks¹, Russell Lagore¹, Jeromy Thotland¹, Uk-Su Choi², Andrea Grant¹, Steve Jungst¹, Nader Tavaf¹, Yigitcan Eryaman¹, Kamil Ugurbil¹, and Gregor Adriany¹
		¹Center for Magnetic Resonance Research, Minneapolis, MN, United States, ²Center for Information and Neural Networks, Osaka, Japan
		We designed an elliptically arranged novel 32-channel Sleeve antenna receiver array for human whole brain imaging at 10.5 tesla. To demonstrate the signal-to-noise ratio (SNR) performance of this array, we evaluated and compared it with a standard 32-channel loop receiver array.

1423		Combining Loops and Dipoles to Increase the Signal-to-Noise Ratio in Human Brain MRI at 7T: How to Shorten a Dipole Antenna?
		Thomas Dardano¹, Rolf Gruetter^1,2, and Daniel Wenz^2,3
		¹Laboratory of Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland, ²CIBM Center for Biomedical Imaging, Lausanne, Switzerland, ³Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
		Dipole antennas can be used in multi-channel loop/dipole arrays to boost the signal-to-noise ratio in MRI at 7T (f=300MHz). For this purpose, dipole antennas need to be physically shorter. In this work we conducted electromagnetic field simulations and phantom experiments at 7T to compare the performance of an inductively-shortened dipole antenna with a dielectrically-shortened dipole antenna in a loop/dipole combination. We evaluated the performance of both designs in different loading conditions and we found that the dielectrically-shortened dipole antenna performed in a very robust manner providing apparent receive field gains when compared with its inductively-shortened counterpart.

1424		Optimization of a massive-element self-decoupled transmit array for 7T head imaging
		Ming Lu^1,2, John C. Gore^1,2, and Xinqiang Yan^1,2
		¹Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States
		At high fields, B1 inhomogeneity is one of the major challenges that limit imaging performance. Parallel transmission with an array of coils is a recognized solution to B1 inhomogeneity. The self-decoupled coil is attractive in Tx array design since it exhibits intrinsic inter-element isolation that may ease the coil fabrication, and allows the dipole mode as well as loop mode. In this work, we evaluated a series of self-decoupled coils in terms of these parameters and aimed to provide guidance for the practical building of a high-performance self-decoupled Tx array.

1425		High-density 72-channel head array at 7Tesla
		Mark Gosselink¹, Tijl van der Velden¹, Hans Hoogduin¹, Martijn Froeling¹, and Dennis W. J. Klomp¹
		¹University Medical Center Utrecht, Utrecht, Netherlands
		A 64 channel head coil receiver is presented that operates with low noise coupling inside a continuously tuned 8-channel transceiver coil. When used as a 72-channel receiver the setup outperforms the default 32 channel receiver array in acceleration, demonstrated by high-resolution MPRAGE images of the human brain.

1426		A 30-element transmit array for 7 Tesla brain imaging with array compressed parallel transmission
		Charlotte Sappo^1,2, Gary R Drake^1,3, Xinqiang Yan^1,3, and William A Grissom^1,2,3,4
		¹Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ³Radiology, Vanderbilt University, Nashville, TN, United States, ⁴Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, United States
		A dense array is desirable for ultra-high field in parallel transmission to better mitigate B₁⁺ field inhomogeneities and control specific absorption rate. Most ultra-high field scanners are limited by the existing number of transmit channels. This limitation can be overcome using array-compressed parallel transmission (acpTx) which enables a small number of channels to drive a large number of coils. This work describes the construction of a 30-loop head transmit array using a mixed overlapped and self-decoupled design with a widely-used commercial 32-channel receive insert for human imaging applications.

1427		SNR of Flexible Versus Rigid Coil Arrays for Knee MRI
		Jeremiah Hess¹, Marianne Black², Feliks Kogan², and Brian Hargreaves^1,2,3
		¹Department of Bioengineering, Stanford University, Stanford, CA, United States, ²Department of Radiology, Stanford University, Stanford, CA, United States, ³Department of Electrical Engineering, Stanford University, Stanford, CA, United States
		Flexible extremity coil-arrays for knee imaging in MRI can improve coil positioning and comfort to patients in the scanner and wrap tightly around the knee, placing coil elements close to anatomy of interest. Despite this, flex coils have not been widely adapted due to perceived superiority of the SNR of transmit-receive coils. In this study, we analyzed the SNR of flex coil-arrays versus a rigid coil-array in phantom and in vivo to determine which coil-arrays had improved SNR. Preliminary results suggest that flexible coil-arrays show comparable or increased SNR and generally more uniform SNR over rigid coil-arrays.

1428		Reduction of coupling and noise by ultrahigh dielectric constant (uHDC) materials for phase array coil at 3T
		Navid PourramzanGandji¹, Christopher T. Sica², Gary W. Yang³, Hannes Wiesner⁴, Soo Han Soon⁴, Xiao-Hong Zhu⁴, Michael Lanagan⁵, Wei Chen⁴, and Qing X. Yang¹
		¹Neurosurgery, Pennsylvania State University, Hershey, PA, United States, ²Radiology, Pennsylvania State University, Hershey, PA, United States, ³Pennsylvania State University, Hershey, PA, United States, ⁴Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, ⁵Materials Science and Engineering, Pennsylvania State University, State College, PA, United States
		Prior work has examined the effects of uHDC material upon phased array coils. Several beneficial effects have been observed: reduction of per-channel noise and inter-channel noise correlations, and enhancement of SNR. Due to the high dielectric constant the electric field will be confined to the dielectric material, which leads to a reduction of the primary noise source, the conservative electric field. As a result the non-conservative field becomes more dominant within the sample, with a resulting increase of B1 field intensity and more substantial SNR enhancement.

1429		A novel characterization method of HTS non-linear electrical properties using MRI
		Aimé Labbé¹, Isabelle Saniour¹, Rose-Marie Dubuisson¹, Jean-Christophe Ginefri¹, Luc Darrasse¹, and Marie Poirier-Quinot¹
		¹Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France
		Decoupling is a major technological challenge of High-Temperature Superconducting (HTS) surface coils. A promising strategy is to exploit nonlinearities in the HTS coil electric response to achieve decoupling. In this work, we present a new characterization method allowing the evaluation of these nonlinearities using MRI. We first present the theoretical model behind this approach; we then proceed to use it on 3D images of a water phantom in the vicinity of a copper coil and then a HTS coil to validate the model through the extraction of the quality factor Q, compared to the one measured by alternative methods.

1430		Robot Assisted Dynamic Ankle Joint Imaging with a Wearable 4-Channel High Impedance Coil at 1.5T MRI
		Matthäus Poniatowski¹, Ilan Elias², Mirsad Mahmutovic¹, Gurinder Multani¹, Sam-Luca J.D. Hansen¹, Markus W. May¹, Alexander M. König³, Jens H. Figiel³, Andreas H. Mahnken³, and Boris Keil¹
		¹Institute of Medical Physics and Radiation Protection, TH Mittelhessen University of Applied Sciences, Gießen, Germany, ²Motionrad GmbH, Berlin, Germany, ³Department of Diagnostic and Interventional Radiology, Philipps-University Marburg, Marburg, Germany
		Limitations of conventional MRI include its lack of ability to observe controlled joint motion and biomechanics in real-time. Although clinically evident, many injuries, instabilities, and dysfunctions of the musculoskeletal system are frequently not depicted on conventional static MRI. To enable dynamic MRI for joints, an in-bore motion-assisted device and a wearable coil array was designed, constructed, and validated. The combination of robotic assisted joint motion, a tight-fitting coil array that does not restrict the joint's range of motion, and accelerated imaging enabled dynamic MRI of the ankle.

Innovative Transmit Coils

RF Design II

Engineering/Interventional/Safety

1571		Design and evaluation of a 2-Tx 24-Rx coil for 5T knee MR imaging
		Shao Che¹, Junjun Qin¹, Shihong Han¹, and Ye Li²
		¹United Imaging Healthcare, Shanghai, China, ²Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Science, Shanghai, China
		Musculoskeletal imaging is one widely used MR application with advantages in exquisite details of anatomic structure, rich contrast options for various soft tissues and high diagnostic accuracy [1]. The SNR gain of high field MRI can further help extending such applications as magnetic resonance knee imaging. A 2-channel birdcage transmit and 24-channel loop array receive coil is designed and evaluated on the novel whole body 5T MRI scanner (United Imaging Healthcare, Shanghai, China, abbreviated as UIH below). The imaging performance is compared with a 3T scanner and the results are discussed.

1572		In-vivo human brain imaging at 5 T using a 48 channel Tx-Rx array
		Ye Li^1,2, Zidong Wei^1,2,3, Shihong Han³, Shuheng Zhang³, Qiang He³, Xiaoliang Zhang⁴, Xin Liu^1,2, and Hairong Zheng^1,2
		¹Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, ²Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, ³United Imaging Healthcare, Shanghai, China, ⁴Department of Biomedical Engineering, State University of New York at Buffalo, NY, NY, United States
		Intermediate field strength between 3 T and 7 T may provide significant signal-to-noise ratio improvement but with less radio frequency challenges. In this work in-vivo human brain images including anatomic images, angiography images and susceptibility weighted images have been acquired at a prototype 5 T whole body scanner using a 48 channel Tx-Rx array, and compared with those at 3 T commercial scanner. Significant signal-to-noise ratio improvement of 5 T has been shown while image homogeneity is still acceptable.

1573		An 8-channel transmit loop array for body imaging at 5T
		Fuyi Fang¹, Wei Luo¹, Jingxia Gong¹, Rongxing Zhang¹, Zidong Wei², and Ye Li²
		¹United Imaging Healthcare, Shanghai, China, ²Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
		In this study, an 8-channel (8ch) loop and a 2-channel (2ch) birdcage in 5T frequency are built and compared. Basic electrical characteristics, engineering issues in implementation, transmitting efficiency, perturbation sensitivity, B1+ uniformity and local SAR are compared between these two coils. Measurement result of the B1+ distribution in torso region with these coils are obtained from a whole body 5T MRI scanner.

1574		Robust decoupling of a 7 Tesla 8-channel loop array for head and cervical spinal cord imaging
		Bei Zhang¹, Abbas Zaki², Daniel Lowrance², Ivan Dimitrov^1,3, Binu Thomas¹, Andreas Pfrommer⁴, and Anke Henning^1,4
		¹Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States, ²Erik Jonsson School of Engineering and Computer Science at The University of Texas at Dallas, Richardson, TX, United States, ³Philips Healthcare, Gainesville, FL, United States, ⁴Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
		With the guidance of our in-house analytical modeling tool that was developed originally for minimizing both electrical coupling and magnetic coupling , we designed a 7T 8-channel T/R array with robust decoupling performance for both head and cervical spinal cord imaging, and our 7T 8 channel array demonstrated robust decoupling performance for both head and cervical spine cord imaging in both simulations and experiments.

1575		Effect on SAR and Transmit Efficiency by Geometrical Configuration of RF Transmit Head Coil for 7 T MRI
		Youngdae Cho¹ and Hyoungsuk Yoo¹
		¹Electronic Engineering, Hanyang University, Seoul, Korea, Republic of
		As the risk of RF heating in UHF MRI due to high specific absorption rate (SAR), recent work to design the coil focused to reduce SAR. In this study, the impact of the geometrical shape of the multi-channel RF head coil on the transmit efficiency (TE) and SAR efficiency (SE) was analyzed. Four different configurations of the head coil were simulated. it is evident from the results that a coil configuration similar to the head shape is required to optimize the TE and SE simultaneously.

1576		A dipole antenna array with “flipped” high dielectric constant (HDC) material for improved SNR at 10.5 Tesla
		Myung Kyun Woo¹, Lance DelaBarre¹, Russell Lagore¹, Steve Jungst¹, Michael T Lanagan², Thane Bonnett², Qing X Yang², Riccardo Lattanzi³, Kamil Ugurbil¹, and Gregor Adriany¹
		¹Center for Magnetic Resonance Research, Minneapolis, MN, United States, ²Penn state University, Centre County, PA, United States, ³Radiology at NYU Grossman School of Medicine, New York University, New York, NY, United States
		In the previous work, we evaluated the transmit performance of 10.5 T RF coils composed of dipole antennas and high dielectric constant (HDC) ceramic materials with a “Normal” (Dipole - HDC - Sample) and a counterintuitive “Flipped” geometry (HDC – Dipole - Sample) positioning. Now we evaluated the receive performance of such an array structure with these setups both in simulations and experiments. The “flipped” setup showed notable periphery SNR improvement and suggest some promise for the UHF receiver arrays.

1577		Development of a Dedicated Mono-surface 16-Element Transceiver Dipole Antenna Array for Parallel Transmission Cardiac MRI in Pigs at 7 Tesla
		Ibrahim A. Elabyad¹, Maxim Terekhov¹, Michael Hock¹, David Lohr¹, and Laura M. Schreiber¹
		¹Chair of Molecular and Cellular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Wuerzburg, Wuerzburg, Germany
		To improve parallel imaging performance for cardiac MRI in pigs at 7T, a dedicated transceiver 16-element antisymmetric dipole antenna array was developed and tested. EMF-simulations were performed with the antisymmetric dipole array loaded with a dedicated pig thorax-shaped phantom. Imaging performance of the dipole array was validated through MR-measurements in a pig phantom and an 85kg pig cadaver. The dipole array demonstrated a threefold improvement in coefficient-of-variation of the measured FA maps after $$${B_1^+}$$$-shimming using the vendor integrated pTx-platform. Parallel imaging with acceleration factor up to R=4 was possible while maintaining a mean g-factor of 1.13 within the pig heart.

1578		Design of a 19-Channel hybrid array system for Foot/Ankle Imaging at 7T
		Aditya Ashok Bhosale¹, Leslie L Ying¹, and Xiaoliang Zhang¹
		¹Biomedical Engineering, University at Buffalo, Buffalo, NY, United States
		Microstrips are being used in MR applications due to their unique properties such as reduced radiation loss, high frequency capability, and reduced perturbation of sample loading to the RF coil compared to conventional coils. In this study, we propose a 19-channel hybrid array consisting of 14 Microstrips and 5 loop coils placed on the foot/ankle phantom to cover maximum area of the subject at 7T.

1579		A 28-channel decoupled Tic-Tac-Toe transmit radiofrequency coil for 7T MRI
		Tales Santini¹, Anthony DeFranco¹, Tiago Martins¹, Andrea Sajewski¹, Howard J. Aizenstein¹, and Tamer S. Ibrahim¹
		¹University of Pittsburgh, Pittsburgh, PA, United States
		In this work, we investigated the potential of the smaller sizes of the Tic-Tac-Toe transmit coil elements, comparing the newly developed uncoupled configuration with the traditional coupled version of this RF coil design. Simulations with 14 Tic-Tac-Toe panels showed excellent levels of transmit field homogeneity at 7T (coefficient of variation = 12.6%, average = 0.28µT for 1W) while maintaining low levels of SAR (SAR efficiency = 1.41 µT/√(W/Kg)). The simulations were validated with phantom experiments. Future work includes the assembling of the 28-channel transmit coil and the investigation of the optimal power splitting strategy.

1580		A Comparative Study Highlighting a Novel UHF MRI Volume Body Coil Design
		Sayim Gokyar¹, Henning U. Voss¹, Victor Taracila², Fraser J. L. Robb², Douglas J. Ballon¹, and Simone Angela Winkler¹
		¹Radiology, Weill Cornell Medicine, New York, NY, United States, ²General Electric Healthcare, Aurora, OH, United States
		We designed a novel 2D cylindrical high-pass ladder (c-HPL) volume body coil by adding a second dimension in S-I direction to the 1D birdcage concept, given that the latter fails at 7T body dimensions. We compared its performance to the (non-functional) 1D birdcage and transverse electromagnetic (TEM) designs. In silico results showed improved B1 homogeneity (inhomogeneity of 15.9%) with lower specific absorption rate (SAR) and better SAR efficiency (0.743 μT/W∙√kg). The proposed architecture is a promising candidate for UHF MRI applications where the current lack of a built-in body coil hinders the modality from gaining full clinical acceptance/approval.

1581		Asymmetric ring birdcage coil for volume excitation
		Hideta Habara¹ and Shinichiro Suzuki¹
		¹Healthcare Business Unit, Hitachi, Ltd., Tokyo, Japan
		Design of asymmetric ring diameter birdcage volume coil has been studied by electromagnetic filed simulations. Even if the diameter of the front and the rear rings of the birdcage coil is changed to some extent with respect to the cylindrical RF shield, the uniformity in the Z direction can be maintained by changing the width of the front and rear rings. Increasing the gap between the ring and the RF shield has an advantage in efficiency even applied on one side of the ring.

1582		Toward Enhanced Transmit Performance of Rectangular Dielectric Resonator Antenna Arrays for 7-T MRI Using Loop/Dipole Coupling Scheme
		Daniel Wenz^1,2
		¹CIBM Center for Biomedical Imaging, Lausanne, Switzerland, ²Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
		This study investigates a loop-dipole coupling scheme as a new approach to excite orthogonal dielectric modes in a rectangular dielectric resonator antenna for MRI at 7T. A rectangular dielectric resonator antenna was simulated, built and its performance was evaluated in phantom experiments using two coupling schemes: dipole-only and loop-dipole. It was found that the loop-dipole coupling scheme can substantially enhance not only transmit performance of a single element, but also of an array of rectangular dielectric resonator antennas (transmit field efficiency gain of 35%).

1583		Development of a Microstrip Tx Coil Module for 7T MRI
		Andrea N Sajewski¹, Tales Santini¹, Matthew Saich¹, Tiago Martins¹, and Tamer S Ibrahim¹
		¹University of Pittsburgh, Pittsburgh, PA, United States
		A 7T microstrip RF coil was designed based on the Tic-Tac-Toe (TTT) concept that has previously shown homogeneity and load-insensitivity. Simulations were performed to compare B₁⁺ distributions between the microstrip TTT and standard TTT coils. A 4-channel microstrip coil was assembled and B₁⁺ maps were acquired at 7T. Nearly equivalent B₁⁺ distributions were observed, indicating the potential for using a highly dense microstrip array to provide excellent homogeneity and reduction of SAR while enabling unique designs, such as conforming to the anatomy of interest.

1584		New commercial 8Tx/16RX array for Clinical 7T Cardiac MRI: initial experience
		Maxim Terekhov¹, David Lohr¹, Theresa Reiter², Ibrahim A. Elabyad¹, Michael Hock¹, and Laura M. Schreiber¹
		¹Chair of Molecular and Cellular Imaging, University Hospital Würzburg, Comprehensive Heart Failure Center, Wuerzburg, Germany, ²Department of Internal Medicine I, Cardiology, University Hospital Würzburg, Wuerzburg, Germany
		7T cardiac MRI is a novel field with the potential to increase the physical sensitivity and diagnostic value of the clinical cardiac images. Multiple elements transmit/receive phased array coils in combination with parallel transmit RF-technology allow for an improvement of the image quality at ultra-high-field (B₀≥7T) field strength. In this work, we present initial experience with a new commercial 8Tx/16Rx thorax array coil operating in a “pTX-Compatibility Mode” of the scanner for cardiac MRI at 7T.

1585		High power RF amplifier for UHF MRI with configurable number of channels
		Jifeng Chen^1,2, Ye Li¹, Han Zhang², Bin Cao², Xin Liu¹, Hairong Zheng¹, and Xu Chu²
		¹Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, ²United Imaging Healthcare, Shanghai, China
		Increasing magnetic field strength can improve signal-to-noise ratio (SNR) of MRI [1] and it requires higher power capability and fidelity from RF Power Amplifier (RFPA). Meanwhile, to reduce B1 inhomogeneity at high field usually requires multi-channel parallel transmission (pTx) technique. In this study, we present a method to design RFPA with high power capability and output linearity, and with configurable number of transmit channels so as to meet different RF coil and load requirements.

1586		Quadrature Tx/Rx wireless coil for targeted breast MRI at 1.5 T
		Viktor Puchnin¹, Anna Hurshkainen¹, Anton Nikulin², Georgiy Solomakha¹, Anna Andreychenko^1,3, and Alena Shchelokova¹
		¹Department of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation, ²Institut Langevin, ESPCI Paris, CNRS, PSL University, Paris, France, ³Research and Practical Clinical Center for Diagnostics and Telemedicine Technologies of the Moscow Health Care Department, Moscow, Russian Federation
		We demonstrate for the first-time a quadrature transceive wireless coil for 1.5T targeted breast MRI. The proposed concept features two volumetric resonators: metamaterial-inspired structure and Helmholtz coil. These coils are electromagnetically coupled to the body birdcage coil and interact with its magnetic field’s components, thus boosting body coil transmit efficiency, SAR efficiency, and receive performance for the targeted area of the human breast.

1587		Circularly polarized coil for 1.5 T MRI RF harvesting
		Pavel Seregin¹, Georgiy Solomakha¹, Egor Kretov², Oleg Burmistrov¹, and Alexey Slobozhanyuk¹
		¹The Department of Physics and Engineering, ITMO University, Saint Petersburg, Russian Federation, ²Max Delbruck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
		The concept of the wireless power supply for the MRI coils demands high efficiency in a restricted volume. To meet these requirements, we investigated the possibility of harvesting the energy from the B1 field of a 1.5 T MRI scanner using a new volumetric coil design. We performed a series of experiments with the different positions of the proposed coil within the scanners bore and estimated the accepted power levels during the different types of MR pulse sequences.

1588		Development of Microstrip Coils Integrated with High Dielectric Constant (HDC) Material to Improve B1 Field and Performance of 1H MR imaging at 7T
		Soo Han Soon^1,2, Matt Waks¹, Xiao-Hong Zhu¹, Hannes M. Wiesner¹, Navid P. Gandji³, Qing X. Yang³, Michael T. Lanagan⁴, and Wei Chen¹
		¹CMRR, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, ²Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States, ³CNMRR, Department of Neurosurgery, Penn State University, Hershey, PA, United States, ⁴Department of Engineering, Penn State University, Hershey, PA, United States
		The development of ultra-high-field (UHF) magnetic resonance imaging (MRI) and spectroscopy imaging (MRSI) technologies improves sensitivity and spatial resolution for biomedical and clinical applications. However, the limited inherent signal-to-noise ratio (SNR) is still challenging, especially for pushing spatiotemporal resolution even at UHF. Previous studies have shown that high dielectric constant (HDC) materials could provide a new RF engineering solution for the challenge. In this study, we introduce a novel microstrip transmission line (MTL) transceiver array that uses HDC material as substrate, and significantly improves the RF transmission (B₁⁺) and reception (B₁^-) fields and SNR for ¹H imaging application at 7T.

1589		A 2D High-Pass Ladder RF Coil Architecture for UHF MRI
		Sayim Gokyar¹, Henning U. Voss¹, Victor Taracila², Fraser J. L. Robb², Michael Bernico³, Douglas Kelley³, Douglas J. Ballon¹, and Simone Angela Winkler¹
		¹Radiology, Weill Cornell Medicine, New York, NY, United States, ²General Electric Healthcare, Aurora, OH, United States, ³General Electric Healthcare Technologies, Waukesha, WI, United States
		We propose a two-dimensional cylindrical high-pass ladder (2D c-HPL) volume coil architecture as a new class of radiofrequency coils to be used for 7T Body MR imaging. As a first simplified experimental proof-of-concept we show feasibility in a head sized coil. In silico results show 45% more homogeneous B1 field distribution with 25% lower specific absorption rate compared to a similar size birdcage coil. Experimental results are in good agreement with theory and numerical simulations. The proposed architecture shows promise to solve the longstanding open challenge of volume coil B1+ inhomogeneity in UHF MRI applications.

1590		Performance comparison of using an external 16-channel transmit array vs. using 16 elements of a 32-channel receive array as transceivers at 10.5 T
		Bei Zhang¹, Gregor Adriany², Navid Pourramzan Gandji³, Qing X. Yang³, Brian Rutt⁴, Jeramie Radder², Lance DelaBarre², Myung Kyun Woo², Kamil Ugurbil², and Riccardo Lattanzi^5,6
		¹Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States, ²Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, ³Department of Radiology, Pennsylvania State College of Medicine, Hershey, PA, United States, ⁴Department of Radiology, Stanford University, Stanford, CA, United States, ⁵Center for Advanced Imaging Innovation and Research (CAI2R) and Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, ⁶The Vilcek Institute at NYU Langone Health, New York, NY, United States
		Shielding effects associated with surrounding the receive array with an external transmit (Tx) array could decrease the signal-to-noise ratio (SNR) at 10.5 T. Two Tx approaches were compared: using 16 receive elements as transceivers vs. using a 16-channel external transmit array. For both cases, the effect of using high-permittivity material (HPM) was evaluated. Our simulation results showed that performance was larger for the transceivers and further increased with HPM. This suggests that the additional complexity associated with constructing a multi-element transceiver array compared to using an external transmitter could be justified for 10.5T imaging by the expected gain in performance.

Innovative Receive Coils

RF Design II

Engineering/Interventional/Safety

1591		Ultra-Flexible, High-Resolution, 60-Channel RF Coil for Supine Breast Imaging
		Jana Vincent^1,2,3, Clyve Konrad Follante¹, Ersin Bayram⁴, Lloyd Estkowski⁵, Ty Cashen⁶, Mark Giancola¹, Victor Taracila¹, Yun-Jeong Stickle¹, Lalit Rai¹, Venkata Malasani¹, Nicole Wake^7,8, Vichiry Yan¹, Robert Stormont⁹, Joseph Rispoli^2,10, and Fraser Robb¹
		¹GE Healthcare Coils, Aurora, OH, United States, ²Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States, ³Basic Medical Sciences, Purdue University, West Lafayette, IN, United States, ⁴Global MR Applications & Workflow, GE Healthcare, Houston, TX, United States, ⁵Global MR Applications & Workflow, GE Healthcare, Waukesha, WI, United States, ⁶Global MR Applications and Workflow, GE Healthcare, Madison, WI, United States, ⁷Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, United States, ⁸Center for Advanced Imaging Innovation and Research, Department of Radiology, NYU School of Medicine, New York, NY, United States, ⁹GE Healthcare, Waukesha, WI, United States, ¹⁰School of Electrical & Computer Engineering, Purdue University, West Lafayette, IN, United States
		Typically, breast MR scans are performed prone; however, there are advantages to supine imaging. Here we present the first 60-channel, high-resolution, flexible breast coil. The coil can be run with the embedded posterior coil for a total of 90-channels in the FOV. In addition to better image quality, with such a high channel count, an acceleration of up to 5 by 2 was possible. Due to the structured shape, breast tissue was kept in place for the duration of the scan and women with cup sizes up to a DD could be accommodated. Straps provide adjustments for smaller bust sizes.

1592		A Continuously Adjustable 32-Ch Head Coil Array for MRI at 3T
		Yunsuo Duan¹, Jiacheng Wang², Feng Liu¹, Rachel Marsh¹, and Thomas J. Vaughan³
		¹MR Research, Department of Psychiatry, NYSPI and Columbia University, New York, NY, United States, ²Department of Electrical Engineering, New York University, New York, NY, United States, ³ZMBBI, Columbia University, New York, NY, United States
		Close fitting is extremely crucial for RF coil arrays in order to maximize sensitivity. It is impossible to closely fit for all subjects of various head sizes using rigid head coil arrays. We presented a novel design of partially flexible 32-channel coil array to address the issue. The inner dimensions of the coil array can be smoothly adjusted from 180mmx220mm to 220mmx 260 mm, which fit for almost all head sizes of adult human subjects. The experiment results showed high imaging quality within the adjustable ranges. The coil array is highly practical for both research and clinical settings.

1593		A Quadrature Birdcage/47Rx Coil Array for Acceleration Images on 3 T MRI
		Jo Lee^1,2, Sen Jia^1,2, Liu Liu³, Xiaoliang Zhang⁴, and Ye Li^1,2
		¹Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, ²Shenzhen Key Laboratory for MRI, Shenzhen, China, ³United Imaging Healthcare, Shanghai, China, ⁴Department of Biomedical Engineering, State University of New York, Buffalo, NY, United States
		We designed and built a quadrature-birdcage/ 47Rx head coil array for accelerated images on 3 T MRI. A 32-channel commercial head coil was used as a comparison. The inverse g-factor images and accelerated anatomical images both show that the 47-channel head coil has better acceleration ability. EPI images and cerebrovascular images further verified that the 47-channel head coil is capable of human’s brain studies.

1594		A dedicated coil for cerebellar fMRI
		Nikos Priovoulos¹, Thomas Roos¹, Ozlem Ipek², Ettore Meliado³, Richard Nkrumah², Dennis Klomp³, and Wietske van der Zwaag¹
		¹Spinoza Center, Amsterdam, Netherlands, ²King’s College London, London, United Kingdom, ³University Medical Center Utrecht, Utrecht, Netherlands
		The function of human cerebellum is underexplored in vivo, due to its small size and its placement at the bottom of the brain where transmit fields are suboptimal at 7Tesla. Here, we combined 2 dense coil arrays of 16 small surface receive elements each with a transmit array of 3 antennas elements. Our results show improved B₁+ and SNR close to the surface as well as g-factor gains compared to a whole-head commercial coil. This resulted in large gains in the surface (< 3.5cm) in the spatial extent of the BOLD activation, at the cost of increased signal inhomogeneity.

1595		A novel multi-turn histology RF coil design for micro-histological slide imaging
		Byung-Pan Song^1,2, Sung-Jun Yoon¹, Hyeong-Seop Kim^1,2, Kyoung-Nam Kim³, and Seung-Kyun Lee^1,2,4,5
		¹Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Korea, Republic of, ²Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Korea, Republic of, ³Department of Biomedical Engineering, Gachon University, Incheon, Korea, Republic of, ⁴Department of Physics, Sungkyunkwan University, Suwon, Korea, Republic of, ⁵IBS Center for Neuroscience Imaging Research, Suwon, Korea, Republic of
		MR microscopy can provide high-resolution measurement of MR properties of biological and artificial tissues that can be compared with optical imaging. In such experiments, low signal-to-noise ratios (SNR) of a common clinical RF coil with a low filling factor will be a challenge. So, we propose a novel, multi-turn histology coil for imaging microscopic tissue histology slices with substantially higher SNR in clinical MRI scanner compared to the previous design for microscopy tissue imaging.

1596		How far Should Coil Coverage be Extended to Reach Optimum Simultaneous Multi-Slice Acceleration in Cardiac MRI?
		Anpreet Ghotra¹, Sam-Luca JD Hansen¹, Robin Etzel¹, Mirsad Mahmutovic¹, Alina Scholz¹, Nicolas Kutscha¹, Matthäus Poniatowski¹, Markus W May¹, Choukri Mekkaoui², and Boris Keil¹
		¹Institute of Medical Physics and Radiation Protection, TH Mittelhessen University of Applied Sciences, Giessen, Germany, ²Harvard Medical School, Massachusetts General Hospital, Department of Radiology, A.A. Martinos Center for Biomedical Imaging, Boston, MA, United States
		Even with commonly used k-space subsampling acceleration methods, cardiac MRI still suffers from relatively slow acquisition speed which imposes limitations in spatial and temporal resolution and volumetric coverage when imaging the moving heart. The recently introduced simultaneous multi-slice (SMS) acceleration technique offers the potential to acquire multiple slices which can substantially increase myocardial coverage without compromising in-plane spatial resolution. However, to disentangle the collapsed slices, array coils must provide enough sensitivity variation along the slice direction. Therefore, in this simulation study, we evaluated the coverage of the cardiac array coil to maximize SMS encoding performance.

1597		A novel 16 channel flexible coil for highly accelerated upper-airway MRI
		Wahidul Alam¹, Rushdi Zahid Rusho¹, Scott Reineke², Madavan Raja², Stanley Kruger³, Joseph M. Reinhardt¹, Junjie Liu⁴, Douglas Van Daele⁵, and Sajan Goud Lingala^1,2
		¹Roy J Carver Department of Biomedical Engineering, University of Iowa, iowa city, IA, United States, ²ScanMed LLC, Omaha, NE, United States, ³Department of Radiology, University of Iowa, iowa city, IA, United States, ⁴Department of Neurology, University of Iowa, iowa city, IA, United States, ⁵Department of Otolaryngology, University of Iowa, iowa city, IA, United States
		We develop a novel custom airway coil that offers significant boost in signal sensitivity in several regions of the upper-airway such as tongue, soft-palate, pharynx, glottis. Our coil is designed to be flexible for easy conformation to the subjects face/neck anatomy. With the proposed coil, we demonstrate robust parallel MRI performance up to R=4-5 fold for static imaging with 1-D under-sampling, and highly accelerated dynamic imaging (up to R~27 fold) of swallowing, and airway shaping due to variations in breathing.

1598		Signal-to-noise of thermal versus hyperpolarized MRI as a function of field strength and receive coil temperature
		Mohammed M. Albannay¹, Charles McGrath¹, Alexander Jaffray¹, and Sebastian Kozerke¹
		¹University and ETH Zurich, Institute for Biomedical Engineering, Zurich, Switzerland
		In this work SNR of thermal and hyperpolarized MRI is simulated based on first principles. It is demonstrated that detection of hyperpolarized nuclei is more favourable at lower field strengths (e.g. 0.75T) where prolonged T₂* values and reduced readout bandwidth lead to higher SNR compared to standard clinical field strengths. Moreover, SNR benefits of receive coil cooling are experimentally studied on a clinical 3T Philips Achieva scanner that has been ramped down to a field strength of 0.75T.

1599		Performance comparison of a 10 cm single-gap vs. double-gap coaxial coil used as a transceiver for 7T MRI
		Lena Nohava^1,2, Andre Kuehne³, Elmar Laistler¹, and Sigrun Roat¹
		¹High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²BioMaps (Laboratoire d'Imagerie Biomédicale Multimodale Paris Saclay), Université Paris-Saclay, CEA, CNRS, Inserm, Orsay, France, ³MRI.TOOLS GmbH, Berlin, Germany
		In this work, we investigated the performance differences between a flexible single-gap coaxial coil operated far above self-resonance and a double-gap coaxial coil operated on self-resonance at 7T. Based on electromagnetic simulations and MRI results it is demonstrated that in the single-gap design the current distribution on the outside of the coaxial shield is strongly inhomogeneous. This leads to a strong dependence of the Tx performance on the coil orientation relative to B₀. In contrast, the double-gap design results in homogeneous current distribution and orientation-independent Tx performance.

1600		Additive manufacturing of MRI coils by printing and electroplating a conductive polymer
		Christoph Michael Schildknecht¹ and Klaas Paul Pruessmann¹
		¹Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zürich, Switzerland
		In this work, additive manufacturing of MRI coils by selectively electroplating a conductive polymer is demonstrated, enabling the fabrication of complex coil geometries with high accuracy and reproducibility. Using a low-cost multi-material FDM 3D printer, deposition of insulating and conductive elements has been achieved in a single process, followed by straightforward electroplating. The proposed approach is demonstrated by an example of a wrist coil, including in-vivo imaging at 3T.

1601		Novel antenna array for ultra-high field MR-PET
		Chang-Hoon Choi¹, Suk-Min Hong¹, Jörg Felder¹, Lutz Tellmann¹, Jürgen Scheins¹, Elena Rota Kops¹, Christoph Lerche¹, and N. Jon Shah^1,2,3,4
		¹INM-4, Forschungszentrum Juelich, Juelich, Germany, ²JARA-BRAIN-Translational Medicine, Aachen, Germany, ³Department of Neurology, RWTH Aachen University, Aachen, Germany, ⁴INM-11, Forschungszentrum Juelich, Juelich, Germany
		Hybrid MR-PET is a powerful imaging technique that capitalised on the advantages of both modalities. However, to optimise these capabilities, the MRI antenna, which is located inside the effective PET detection area, needs to be operated without compromising any aspects of system performance or image quality compared to the stand-alone instrumentation. Here, we report a novel J-pole antenna array concept which is gamma radiation transparent. Furthermore, this unique feature provides advantages in MR-only applications by reducing the coupling effect between cables and the antenna elements and by lowering the potential specific absorption rate burden.

1602		Decomposition of the incomplete volume-surface integral equation matrices for MR coil simulations
		Ilias Giannakopoulos¹, Georgy Dmitrievich Guryev², Jose Enrique Cruz Serralles², Ioannis Georgakis¹, Luca Daniel², Jacob White², and Riccardo Lattanzi^1,3,4
		¹Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States, ²Department of Electrical & Computer Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States, ³The Bernard and Irene Schwartz Center for Biomedical Imaging (CBI), Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States, ⁴Vilcek Institute of Graduate Biomedical Sciences, New York University Grossman School of Medicine, New York, NY, United States
		The volume-surface integral equation (VSIE) method is used for rapid and accurate simulations of electromagnetic fields in magnetic resonance imaging. For the case of a 7T array and a numerical head phantom, we constructed the VSIE coupling matrix that models the interactions between the coil and the scatterer. We reshaped the columns of the matrix as incomplete 3D tensors. We investigated how the low rank properties of these tensors, could be exploited to compress the coupling matrix, by expressing the tensors in their canonical form. We showed that an excellent compression could be achieved with an error lower than 2%.

1603		Flexible Body Coil for Vertical Field MRI using Loop/CRC RF Coil Array
		Yosuke Otake¹, Takeshi Taniguchi¹, Hideta Habara¹, Christophor Napier², Errol Brissett², Shawn Etheridge², Masayoshi Dohata¹, and Kazuyuki Kato¹
		¹Healthcare Business Unit, Hitachi, Ltd., Tokyo, Japan, ²Hitachi Healthcare Americas, Twinsburg, OH, United States
		To improving the SNR and the usability in the vertical field MRI(Open MRI), a flexible body(spine/torso) coil has been developed. The coil consists of loop/CRC hybrid multi-channel array (LCA). The performance of the coil was evaluated in phantom experiment at 1.2T vertical field MRI. The SNR of the coil using LCA was 46% better than a conventional body coil. This technique will contribute to improve the performance of the vertical field MRI.

1604		Design of an over-overlapped wearable 3T pelvic phased array using a capacitor-terminated coaxial coil
		Ming Lu^1,2, Junzhong Xu^1,2, Sandeep S. Arora³, John C. Gore^1,2, and Xinqiang Yan^1,2
		¹Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, ³Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT, United States
		Prostate cancer is one of the leading causes of cancer death among men in the US. MRI is a useful tool to assess the presence and extent of prostate cancer, and diagnostic accuracy relies on acquiring images with high SNR. We aimed to improve the performance of such arrays by using flexible coaxial coil technology and an over-overlapping layout to increase the number of coil elements without sacrificing coil size.

1605		An Integrated Radio-Frequency/Wireless (iRFW) Coil Design for Wireless Q-Spoiling During MR Imaging
		Jonathan Cuthbertson^1,2, Trong-Kha Truong^1,2, Jasmine Chen^1,2, Fraser Robb³, Allen W. Song^1,2, and Dean Darnell^1,2
		¹Medical Physics Graduate Program, Duke University, Durham, NC, United States, ²Brain Imaging Analysis Center, Duke University, Durham, NC, United States, ³GE Healthcare, Aurora, OH, United States
		The integrated RF/wireless coil design allows for simultaneous MR image acquisition and wireless data transfer with the same coil element in order to reduce the number of wired connections in the scanner. Here, we use this coil design to wirelessly transmit the scanner trigger signal to perform the Q-spoiling required for MR imaging. Proof-of-concept experiments in a phantom showed that this coil design was able to accurately and reliably transmit the scanner trigger from the adjacent console room to a WiFi-enabled module in the scanner bore, while having minimal impact on the image SNR or wireless performance.

1606		Universally Sized, High-Resolution and ASSET Optimized AIR Cervical Coils Combined with a 48-Channel Head Coil for 3T MRI
		Yun-Jeong Stickle¹, Clyve Konrad Follante¹, Mark Giancola¹, David Anderson¹, Fraser Robb¹, Thomas Stickle¹, Robert Stormont², Holly Blahnik², Ho-Joon Lee³, Young Han Lee⁴, and Darryl B. Sneag⁵
		¹GE Healthcare Coils, Aurora, OH, United States, ²GE Healthcare, Waukesha, WI, United States, ³Haeundae Paik Hospital, Busan, Korea, Republic of, ⁴Severance hospital, Yonsei University, Seoul, Korea, Republic of, ⁵Hospital for Special Surgery, New York, NY, United States
		Conventional high density phased-array head/neck coils are designed to tightly conform to head/neck region to increase SNR and accommodate higher acceleration, which in turn limits space and their use for larger patients. This study shows results for two different universally sized AIR (Adaptive Imaging Receive) neck/cervical spine coils combined with a 48-Channel head coil to provide higher SNR and improved acceleration compared to a conventional coil. 3T MRI setups to image the head/neck, carotids and cervical spine were designed and constructed. Phantom measurements and high-resolution in vivo imaging were performed to demonstrate design performance.

1607		Development of a multiplexed ERETIC-RF array coil for quantitative whole brain 3D-MR spectroscopic imaging (MRSI)
		Bijaya Thapa^1,2, Bernhard Strasser^1,2, Xianqi Li^1,2, Jason Stockman^1,2, Azma Mareyam¹, Boris Keil³, Zhe Wang⁴, Stefan Carp^1,2, Yulin V. Chang⁴, Lawrence Wald^1,2, Philipp Hoecht Hoecht⁵, and Ovidiu Andronesi^1,2
		¹Dept. of Radiology, MGH, A. A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Mittelhessen University of Applied Science, Giessen, Germany, ⁴Siemens Medical Solutions USA, Charlestown, MA, United States, ⁵Siemens Healthcare, Erlangen, Germany
		An Electronic REference To access In vivo Concentrations (ERETIC) to absolutely quantify the brain metabolites for 3D-MRSI using an array coil was developed. The challenge of ERETIC for large receive arrays is that the addition of many ERETIC channels might negatively impact B0 and B1 homogeneity and increase the unwanted channel cross-talk. Here we investigated whether the number of ERETIC channels can be reduced below the number of RF receive elements. We also developed a unique method to coil combine the ERETIC and receive array signal. Metabolite concentration maps obtained with ERETIC were compared to internal water reference method.

1608		New approach to Improve Sensitivity of Implantable NMR microprobe through Electrical Modelization
		José Antonio BERNARDO¹, Abel Rangel Trejo¹, Lucas Werling², Wilfried Uhring², Luc Hebrard², Youssef Zaim Wadghiri³, Christian Gontrand⁴, and Latifa Antonio Fakri-bouchet⁵
		¹Univ Lyon, CNRS, Université Claude Bernard Lyon 1, Institut des Sciences Analytiques, UMR 5280, Villeurbanne, France, ²Icube Laboratory, UMR –CNRS 7357, Université de Strasbourg, Strasbourg, France, ³Grossman School of Medicine, New York University, New York, NY, United States, ⁴INL(Institut des nanotechnologies de Lyon), INSA (Institut National des Sciences Appliquées) Lyon, CNRS, Université Claude Bernard Lyon1, Villeurbanne Cedex, France, ⁵Univ Lyon, CNRS, Université Claude Bernard Lyon 1, Institut des Sciences Analytiques, UMR 5280, INSA Lyon (Institut National des Sciences Appliquées), Villeurbanne, France
		In this study, we propose an original modelling platform 3D-TLE (Transmission Line Extractor) to determine NMR coil and microcoil performance from their geometry. Each part of our microcoil (region of interest $(ROI \sim 2µL-3µL))$, active part, Transmission Line (TL), micro-wire connection (underpass-vias) and the substrate is modelled by an electrical circuit and each contribution to the equivalent resistance is quantified. Our platform allows predicting the optimized microcoil geometry related to expected performances in terms of $Q-factor$ and the signal-to-noise ratio $(SNR)$.

1609		Exploring parallel imaging performance for prostate imaging at 7T using a 72-channel receive array
		Tijl van der Velden¹, Mark Gosselink¹, Ingmar Voogt², Martijn Froeling¹, Hans Hoogduin¹, Dennis Klomp¹, Bart Steensma¹, and Alexander Raaijmakers^1,3
		¹UMC Utrecht, Utrecht, Netherlands, ²Wavetronica, Utrecht, Netherlands, ³Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
		In this study we investigate the parallel imaging performance of a 72 channel body array for 7 tesla. G-factor maps and T2w prostate images have been acquired in a healthy volunteer. Accelerations of 3x3 and 4x1 are feasible without detrimental g-factor penalties.

1610		Coaxial coil modules as building blocks of individually arranged receive-only coil arrays
		Michael Obermann¹, Sigrun Roat¹, and Elmar Laistler¹
		¹High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
		Close form-fitting and adaptation of the RF coil array to the target anatomy are key for obtaining high SNR. We combine ultra-flexible coaxial coils with a modular setup to achieve form-fitting by coil flexibility and adaptive coverage of the assembled array through modularity. In this work, the robustness of the coil characteristics upon reconfiguration of three modules in different array arrangements, was investigated and demonstrated its feasibility without compromise in coil performance.

MRI & Implants: The Good, The Bad & The Ugly

Safety

Engineering/Interventional/Safety

2279		Using deep neural networks to predict RF heating of implanted conductive leads exclusively from implant trajectory and RF coil features
		Jasmine Vu^1,2, Bach T Nguyen², Bhumi Bhusal², Justin Baraboo^1,2, Joshua Rosenow³, Ulas Bagci ², Molly G Bright^1,4, and Laleh Golestanirad^1,2
		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, ⁴Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
		Safety risks associated with radiofrequency (RF) heating of tissue around implanted leads limit MRI accessibility for patients with active electronic implants such as those with deep brain stimulation (DBS) devices. RF heating is highly sensitive to the trajectory of the implanted lead, and full-wave electromagnetic simulations are currently the standard method for quantifying RF heating, requiring extensive computational resources and simulation time. Here, we present a promising, fast approach for predicting trajectory-specific maximum local specific absorption rate (SAR) in the tissue around tips of implanted lead models using deep learning.

2280		RF-Induced Heating of Medical Devices in an Open Bore MRI
		Seoggwan Kim¹, Amy Kester¹, Alan R. Leewood¹, and David C. Gross¹
		¹MED Institute Inc., West Lafayette, IN, United States
		The goal of this study was to develop a computational model that can accurately predict the radiofrequency (RF) induced temperature rise of medical devices in a 1.2T (49 MHz) Hitachi Oasis open bore system for the purpose of MRI labeling according to ASTM F2503. A comparison of experimental and analytical temperature rise of calibration rods, a stent, and a knee implant within a gel phantom was conducted. Simulations of RF heating of the stent and knee implant within the Duke virtual human model were compared for the 1.2T Hitachi Oasis open bore and 1.5T Siemens Avanto closed bore MRI systems.

2281		RF Impedance of MR-Conditional Pacemaker Leads when Connected to Implantable Pulse Generators from Different MR-Conditional Systems
		David Prutchi¹, Jason Meyers¹, and Ramez Shehada²
		¹Impulse Dynamics (USA) Inc., Marlton, NJ, United States, ²Medical Technology Laboratories, La Mirada, CA, United States
		RF-induced heating of an active implantable medical device (AIMD) composed of a pulse generator (IPG) and leads depends on the transmission line impedance of the lead and its proximal-end termination by the impedance of the IPG. We demonstrate that the RF impedance of IPGs is minimal relative to that of the leads, which dominates the overall impedance of the implantable system. Accordingly, mixed hybrid systems composed of MR-Conditional leads and any MR-conditional IPG are expected to have a comparable overall impedance and consequently produce the same RF-induced heating as their corresponding original systems specified by the manufacturers.

2282		Importance of Pacemaker Lead Preconditioning for MR Safety In-Vitro Studies
		David Prutchi¹, Jason Meyers¹, and Ramez Shehada²
		¹Impulse Dynamics (USA) Inc., Marlton, NJ, United States, ²Medical Technology Laboratories, La Mirada, CA, United States
		This study investigates the change in the RF filtering characteristics of the leads of active implantable medical devices (AIMDs) as body fluids seep into the leads during the initial post-implant period. Our findings indicate that the RF characteristics change dramatically with fluid absorption, making it necessary to precondition the leads by soaking in isotonic saline solution to simulate the in-vivo scenario when conducting in-vitro MR safety testing. Furthermore, leads designed with RF-attenuating lumped inductances must consider the effect of fluid absorption on changing the peak RF attenuation frequency.

2283		Radio-Frequency Induced Heating of Hip and Knee Implants in the Cylindrical and Planar Systems
		Kyoko Fujimoto¹, Tayeb A Zaidi¹, Dave Lampman², Josha W Guag¹, Shawn Etheridge², Hideta Habara³, and Sunder S Rajan¹
		¹Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, MD, United States, ²Hitachi Healthcare Americas, Twinsburg, OH, United States, ³Healthcare Business Unit, Hitachi, Ltd., Tokyo, Japan
		Radio-Frequency (RF) induced thermal injury is a common adverse event reported to US Food and Drug Administration. RF-induced heating risk depends on the interaction of implantable medical devices with electric field distribution in the MRI systems. A study showed that RF-induced heating of a neuromodulation device was much lower in the planar system compared to the cylindrical system. In this study, the hip and knee implants were studied in an anatomical human model at a 1.2T planar system and a 1.5T cylindrical system.

2284		Validation of a new 64MHz RF exposure system for testing medical implants for RF-induced heating according to ASTM-F2182 and ISO/TS 10974
		Finya Ketelsen^1,2, Kevin Kröninger², and Gregor Schaefers^1,3
		¹MRI-STaR - Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany, ²TU Dortmund University, Dortmund, Germany, ³MR:comp GmbH, Testing Services for MR Safety & Compatibility, Gelsenkirchen, Germany
		To determine the RF-induced heating of implants, it is necessary, that the RF field source used for testing fulfills several requirements. This study introduced the validation of a new developed linear exposure system for testing. The results for E-Field distributions from numerical simulations are validated experimentally by measuring these E-field distributions. Furthermore, the temperature rise at the 100mm titanium rod is compared with the target values form ISO/TS 10974 Annex I. The system fulfills the requirements and is suitable for testing active and passive implants for RF-induced heating according to ASTM F2182 and ISO/TS 10974.

2285		MRI in patients with a cerebral aneurysm clip; Guideline in the Netherlands
		Mark BM Hofman¹, Cristina Lavini², Albert van der Zwan³, Carola van Pul⁴, Sara H Muller⁵, Mette K Stam⁶, Marinette van der Graaf⁷, Carla Kloeze⁸, Bastiaan J van Nierop⁹, Wouter Teeuwisse¹⁰, Peter Kappert¹¹, Evie EM Kolsteren¹², Kristie Venhorst¹², and Joost PA Kuijer¹³
		¹Radiology and Nuclear Medicine, Amsterdam UMC, Vrije Universiteit, Amsterdam, Netherlands, ²Radiology and Nuclear Medicine, Amsterdam UMC location AMC, Amsterdam, Netherlands, ³, Neurology and Neurosurgery, UMC Utrecht Brain Center, Utrecht, Netherlands, ⁴Maxima Medical Centre, Eindhoven, Netherlands, ⁵Antoni van Leeuwenhoek Hospital, Amsterdam, Netherlands, ⁶Radiology, LUMC, Leiden, Netherlands, ⁷Imaging, Radboud UMC, Nijmegen, Netherlands, ⁸Catharina Hospital, Eindhoven, Netherlands, ⁹Radiology and Nuclear Medicine, University Medical Centre Utrecht, Utrecht, Netherlands, ¹⁰CJ Gorter Center for High Field MRI, LUMC, Leiden, Netherlands, ¹¹Radiology, UMCG, Groningen, Netherlands, ¹²Knowledge Institute Medical Specialists, Utrecht, Netherlands, ¹³Radiology and Nuclear Medicine, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
		The Dutch Association of Medical Specialists wrote a guideline for MR safety experts for an MRI examination in a patient with a cerebral aneurysm clip for known and unknown clip types. Risk stratification for unknown clip types was based on a survey in the Netherlands that identified time frames and locations of ferromagnetic clip use.

2286		Pediatric Patient Positioning Can Reduce Local-SAR at the Pacemaker Lead-tip During MRI Exams
		Jessica A. Martinez¹ and Daniel B. Ennis^1,2,3
		¹Department of Radiology, Stanford University, Stanford, CA, United States, ²Cardiovascular Institute, Stanford University, Stanford, CA, United States, ³Maternal & Child Health Research Institute, Stanford University, Stanford, CA, United States
		Pediatric patients with cardiac implantable electronic devices (CIEDs) are generally contraindicated for MRI exams. Previous work in the adult population suggests that RF heating strongly depends on the patient’s position and orientation within the MRI scanner. The objective of this work was to evaluate in silico several pediatric patient-positions within the MRI scanner as methods to reduce RF-heating.

2287		RF safety simulation of 128-channel EEG net on a 29-month-old whole-body model at 3T
		Hongbae Jeong^1,2 and Giorgio Bonmassar^1,2
		¹Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ²Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Boston, MA, United States
		In this study, RF heating of an EEG on a 29-month-old whole-body voxel model in a 3T MRI was studied with numerical simulation using Sim4Life. 128-channel EEG leads and electrodes were drawn on the head of the 29-month-old voxel model, and the position of the EEG electrodes was estimated from the 3D scan of the EEG net. The 10gSAR_max and the SAR_head were assessed in the model with and without the EEG net in birdcage transmit body coil at 3T. In both cases, estimated results of SAR were well-below the RF safety limit in the international standard.

2288		Experimental validation of simulated implant heating induced by switched gradient fields
		Rüdiger Brühl¹, Thomas Schwenteck¹, Bernd Ittermann¹, Fabio Baruffaldi², Alessandro Arduino³, Umberto Zanovello³, Luca Zilberti³, Mario Chiampi³, and Oriano Bottauscio³
		¹Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany, ²IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy, ³Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
		Switching MR gradients induce eddy-currents in metallic implants. Gradient-aggressive MR sequences were used on a commercial 3 T scanner to heat orthopaedic prostheses ex vivo. Heating experiments are presented, and the measured temperature evolution is compared with corresponding numerical results. Numerical simulations have been successfully validated for five MR sequences at different implant position and orientations in the gradient field.

2289		Numerical Simulation study on the effects of intentionally inhomogeneous E-field distributions on RF-induced heating of implants
		Vincent Hammersen¹, Finya Ketelsen¹, Andreas Rennings², and Gregor Schaefers^1,3
		¹MRI-STaR Magnetic Resonance Institute for Safety Technology and Research GmbH, Gelsenkirchen, Germany, ²General and Theoretical Electrical Engineering (ATE), University of Duisburg-Essen, Duisburg, Germany, ³MR:comp GmbH, Gelsenkirchen, Germany
		RF-induced heating of implants is strongly dependent on the E-Field magnitude at the test location, which is why a universal ±1dB and ±20° phase shift target field value limit is applied. We used numerical simulation to vary the exposing E-Fields, while keeping a constant average E-field magnitude at the test location. Strong deviations in heating development could be observed. In a second step we added phase shifts between exposition sources. The results suggest that, in addition to the limits, the exact field distribution especially the E-field directions should also be taken into account in critical inhomogeneous cases.

2290		Lead electromagnetic models for RF-induced heating in multi-electrode cortical implants
		Mubashir Hussain¹ and Gregor Schaefers^1,2
		¹Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany, ²MR:comp GmbH, Testing Services for MR Safety & Compatibility, Gelsenkirchen, Germany
		This work focus on estimating the RF-induced deposited power at the multi-electrode array of cortical implant (CorTec GmbH, Germany) by means of lead electromagnetic models (LEM). To develop the LEM for such a complex structure, we computed the transfer function for each of the electrode and generated a set of artificial tangential electric fields for validation of the LEM. The transfer functions and the tangential electric fields along the leads are then used to develop the LEM which can estimate the deposited power at the electrode array for an arbitrary lead pathway.

2291		Numerical Modelling of a Close-fitting 8-channel Transceiver Head Coil and EEG Electrodes for Safety Validation at 7T
		Paul Mcelhinney¹, Sarah Allwood-Spiers², Gavin Paterson¹, Marios Philiastides¹, and Shajan Gunamony¹
		¹University of Glasgow, Glasgow, United Kingdom, ²NHS Greater Glasgow and Clyde, Glasgow, United Kingdom
		Simultaneous use of EEG and fMRI at high fields (UHF, ≥7T) offers the dual benefits of a high spatial resolution as well as the ability to study dynamic brain processes. A close fitting coil design has been built for this purpose, having open access to the subject and the EEG hardware while maintaining excellent performance characteristics. We present here the results from computer simulations of the head coil, including the EEG cap using human body models for safety validation and optimization of the design.

2292		MRI in patients with a prosthetic heart valve, annuloplasty ring or mitra clip; Guideline in the Netherlands
		Mark BM Hofman¹, Carla Kloeze², Bastiaan J van Nierop³, Sara H Muller⁴, Joost PA Kuijer¹, Kristie Venhorst⁵, Cristina Lavini⁶, Mette K Stam⁷, Carola van Pul⁸, Wouter Teeuwisse⁹, Marco JW Gotte¹⁰, Peter Kappert¹¹, Evie EM Kolsteren⁵, and Marinette van der Graaf¹²
		¹Radiology and Nuclear Medicine, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands, ²Catharina Hospital, Eindhoven, Netherlands, ³Radiology and Nuclear Medicine, University Medical Centre Utrecht, Utrecht, Netherlands, ⁴Antoni van Leeuwenhoek Hospital, Amsterdam, Netherlands, ⁵Knowledge Institute Medical Specialists, Utrecht, Netherlands, ⁶Radiology and Nuclear Medicine, Amsterdam UMC location AMC, Amsterdam, Netherlands, ⁷Radiology, LUMC, Leiden, Netherlands, ⁸Maxima Medical Centre, Eindhoven, Netherlands, ⁹CJ Gorter Center for High Field MRI, LUMC, Leiden, Netherlands, ¹⁰Cardiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands, ¹¹Radiology, UMCG, Groningen, Netherlands, ¹²Imaging, Radboud UMC, Nijmegen, Netherlands
		Can a patient with a prosthetic heart valve, annuloplasty ring or a mitra clip undergo an MRI examination? The Dutch Association of Medical Specialists (FMS) wrote a guideline, using searches of guidelines, literature, implant databases, and incident databases. The recommendation is: scan the patient with a prosthetic heart valve, annuloplasty ring or mitra clip with an 1.5T or 3T whole body MRI system with a horizontal closed bore superconducting magnet without further restrictions.

2293		Comparing RF Heating Based on SAR vs. B1+RMS MRI Conditional Labeling
		Negin Behzadian¹ and Shiloh Sison²
		¹Research and Development, Abbott, Sylmar, CA, United States, ²Research and Development, Abbott, Sunnyvale, CA, United States
		MRI RF heating can cause thermal damage to biological tissues, especially in patients with leaded implantable devices, by concentrating power deposition at the implant-tissue interface. With the emergence of B_1+RMS as a more precise RF exposure metric than SAR, implantable device manufacturers have begun MR conditional labeling to fixed B_1+RMS levels, in addition to SAR labeling. Our study characterizes the relationship between RF heating per SAR vs. B_1+RMS-based scaling methods in the context of 3T Normal Operating and First Level Controlled Mode MRI exposure.

2294		Quantification of safety and image quality in low field MRI in the presence of medical implants.
		Camille D.E. Van Speybroeck¹, Wouter M. Teeuwisse¹, Tom O'Reilly¹, Paul M. Arnold², and Andrew G. Webb¹
		¹G.J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands, ²Neurosurgery, Carle Foundation Hospital, Urbana, IL, United States
		Very little quantitative data exist on safety aspects of medical implants in low field MRI systems. Protocols for clinical scanners must be adjusted due to differences in bore size and B₀ direction. We present measured and simulated data on magnetically induced displacement forces, image artifacts and SAR on a 50 mT portable MRI system. Results show that some implants must be considered MR unsafe even at 50 mT, that image artifacts are less compared to 3 T even with much lower gradient strengths, and SAR limits can be breached if using very short pulses and inter-echo times in TSE sequences.

2295		A Single Setup Approach for the MRI-based Measurement and Validation of the Transfer Function of Elongated Medical Implants
		Peter Stijnman^1,2, Arcan Erturk³, Cornelis van den Berg¹, and Alexander Raaijmakers^1,2
		¹Computational Imaging, UMC Utrecht, Utrecht, Netherlands, ²Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, ³Medtronic, Minneapolis, MN, United States
		A new method to validate the transfer function (TF) of linear implants was developed, using an independent RF transmitter. A simulation study was performed exploring different methods to change the incident electric field, local transmit coils positioned at various locations is most effective for the validation. A benefit is the constant position of the leap tip and the temperature probe. We performed a TF measurement and validation study for three leads. The simulated incident electric fields of the local transmit coils and the measured TF were used to predict tip heating, verified by temperature probe measurements showing excellent agreement ($$$R^2\geq0.977$$$).

2296		Analysis on 1.5T MR clinical scan time of patients from multiple imaging centers
		Yuqing Wan¹, Nathan Ooms², Paul Nguyen¹, and Guangqiang (Jay) Jiang¹
		¹Axonics Modulation Technologies, Irvine, CA, United States, ²Purdue University, West Lafayette, IN, United States
		This study reported magnetic resonance imaging (MRI) examination duration of 974 patients collected from two imaging sites. Statistical scan time analysis was performed, and distributions were obtained for different scan regions. Scan time disparities were found between the two imaging sites due to the sequence selections and configuration, which may impact imaging cost and image quality. The clinical examination duration data provides useful information for implant device manufacturers to define practical MRI conditions that improve the patients’ overall MR experience.

2297		An anthropomorphic phantom for deep brain stimulation MRI safety investigations
		Benson Yang^1,2, Fred Tam¹, Benjamin Davidson³, Clement Hamani^3,4, Nir Lipsman^1,3,4, Chih-hung Chen², and Simon J Graham^1,5
		¹Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada, ²Electrical and Computer Engineering, McMaster University, Hamilton, ON, Canada, ³Division of Neurosurgery, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, ⁴Harquail Centre for Neuromodulation, Sunnybrook Research Institute, Toronto, ON, Canada, ⁵Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
		Magnetic resonance imaging of deep brain stimulation (DBS) patients remains a safety concern at higher magnetic fields strengths. Phantoms play an important role in validating and estimating patient safety conditions. However, conventional phantoms are typically simple homogeneous structures that limit the ability to replicate DBS surgical implant procedures. In this work, a new phantom structure is proposed with more human-like realism and compartments to enable improved replication of DBS device placement geometries. Preliminary radiofrequency heating results demonstrate significant differences in temperature elevations when the phantom is assembled in a heterogeneous and homogeneous configuration.

SAR & RF Heating

Safety

Engineering/Interventional/Safety

2298		Compact 3T MRI for patients with implanted devices: Software tool to display MR fields at a specified location
		Lydia Jean Bardwell Speltz^1,2, Yunhong Shu², Myung-Ho In², Nolan Meyer^1,2, Erin Gray², Diana Lanners², Yihe Hua³, Robert E Watson², John Huston III², Thomas KF Foo³, and Matt A Bernstein²
		¹Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, United States, ²Department of Radiology, Mayo Clinic, Rochester, MN, United States, ³GE Global Research, Niskayuna, NY, United States
		Many implanted devices are labeled MR Conditional, meaning specific, labeled conditions must be met to ensure safe scanning. We developed a software tool for use with a high-performance, compact 3T (C3T) scanner that verifies relevant MR conditions can be met at the location of the device (e.g., abdomen), even if those conditions are exceeded at the level of the anatomy being scanned (e.g., brain). MR parameters assessed include main magnetic field strength, gradient slew rate, RF amplitude (B1+²), and dB/dz. The limited extent of the fields with C3T suggests high-performance exams can sometimes be obtained without compromising patient safety.

2299		Patient specific parallel transmit pulses are patient position dependent while safety models are fixed: safety implications
		Emre Kopanoglu¹
		¹CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom
		Pulses designed using patient-specific B₁⁺-maps are inherently patient position dependent, while safety models (available on scanners) used for local SAR supervision are not. The effect of this positional mismatch on SAR estimation was investigated for 1-/2-/3-/4-/5-spoke pulses. The results showed substantial underestimation of local SAR: the actual local SAR at off-centre positions was observed to be up to 4.6-fold higher compared to the peak estimated using a centred model. This behaviour was worse for more spokes and consistent across slices between cerebellum and crown. Using multiple distributed models reduced the likelihood of SAR underestimation, but at the cost of over-restrictiveness.

2300		Assessing the In-Vivo RF Heating Effects of Short-Duration B1+RMS in MRI Sequences
		Negin Behzadian¹ and Shiloh Sison²
		¹Research and Development, Abbott, Sylmar, CA, United States, ²Research and Development, Abbott, Sunnyvale, CA, United States
		Exposure to the RF energy of an MRI shall be limited to prevent potential harm to biological tissues. Whole-body SAR, averaged over any 6-minute interval, shall be limited to 2W/kg and 4W/kg under the limits of Normal and First Level Controlled Operating Mode, respectively, and is further restricted to twice the operating mode limit over any 10-second period. Our study investigates whether similar short-duration assessments are necessary for the alternative RF exposure metric of B_1+RMS, in the context of RF heating safety of cardiac protocols with leaded cardiac implants.

2301		Validation of SAR Management Procedure for Dynamic pTx RF Waveforms Using a Self-Built Coil at 7 Tesla
		Sydney Nicole Williams¹, Sarah Allwood-Spiers², Paul McElhinney¹, Yuehui Tao³, John E. Foster², Shajan Gunamony^1,4, and David A. Porter¹
		¹Imaging Centre of Excellence, University of Glasgow, Glasgow, United Kingdom, ²MRI Physics, NHS Greater Glasgow & Clyde, Glasgow, United Kingdom, ³Siemens Healthcare Ltd., Glasgow, United Kingdom, ⁴MR CoilTech Limited, Glasgow, United Kingdom
		Parallel transmit (pTx) can reduce B₁⁺ field inhomogeneity present at 7T, but needs additional consideration for specific absorption rate (SAR) monitoring due to the superimposed electromagnetic fields. For self-built pTx coils, validation includes comparing electromagnetic field simulations with experimental B₁⁺ maps and thermometry, previously presented for static pTx in a self-built 8Tx/32Rx coil. We present full-waveform pTx validation with two further tests: comparison of measured and prescribed RF waveforms, and calculation of local SAR with virtual observation points (VOPs) for all pTx pulses with comparison to scanner predictions and measurements. After validation, dynamic pTx is performed in vivo.

2302		Individualized and accurate SAR characterization method based on an equivalent circuit model in MRI system
		Weiman Jiang¹, Fan Yang¹, and Kun Wang¹
		¹GE Healthcare, Beijing, China
		This work proposed a novel SAR characterization method based on an equivalent circuit model and the circuit’s frequency response analysis. Comparing to well recognized pulse energy method defined in NEMA MS 8, this method doesn’t need the flux loop fixed on transmit coil. Meanwhile, it can monitor SAR accurately. The Root Mean Square (RMS) error and maximum error of the novel method relative to the method in NEMA MS 8 are 4.96% and 9.47% respectively. This method could avoid design complexity of integrating the flux loop and has potential to be easily realized in most MRI scanners.

2303		A local SAR compression algorithm with improved compression, speed and flexibility
		Stephan Orzada¹, Thomas M. Fiedler¹, Harald H. Quick^2,3, and Mark E. Ladd^1,2,4,5
		¹Medical Physics in Radiology (E020), German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany, ³High-Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, ⁴Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany, ⁵Faculty of Medicine, University of Heidelberg, Heidelberg, Germany
		For parallel transmit systems, control of local SAR is very important to ensure safety. For pulse calculation and online supervision, compression of the SAR matrices is used to reduce calculation effort. The original clustering method by Eichfelder et al. was later outperformed by a method proposed by Lee et al. We propose an enhancement to Lee’s algorithm that further increases compression efficiency, speed and flexibility by iteratively reducing the overestimation.

2304		Validation of a Temperature Prediction Workflow for Imaging Complete Deep Brain Stimulation Systems
		Alireza Sadeghi-Tarakameh¹, Nur Izzati Huda Zulkarnain¹, Noam Harel¹, and Yigitcan Eryaman¹
		¹Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, MN, United States
		We validate a previously proposed temperature prediction workflow for a complete DBS Systems undergoing MRI. Accuracy of the workflow is investigated for different termination conditions using an extension cable and an implantable pulse generator (IPG) device. The workflow accurately predicted the temperature time-course during the MRI scan for different trajectories and terminations.

2305		Radiofrequency peak B1+ Survey of commercial 3T MR Systems
		Xin Huang¹, Vick Chen¹, and Shiloh Sison¹
		¹Abbott Laboratories, Sunnyvale, CA, United States
		To determine the appropriate peak B1+ field levels, an RF peak B1+ survey is performed on commercial 3T MR systems loaded with ASTM phantom filled with saline. The peak B1+ averaged over center slab inside the 3T commercial MR systems can be as high as 27 µT. The 3T MRI safety assessment should include values up to this level.

2306		Impact of 1.5T SAR Limits on the MRI Scan Time for Implantable Devices
		Yuqing Wan¹, Nathan Ooms², Paul Nguyen¹, and Guangqiang (Jay) Jiang¹
		¹Axonics Modulation Technologies, Irvine, CA, United States, ²Purdue University, West Lafayette, IN, United States
		Implant device manufacturers often specify a RF exposure limit based on specific absorption rate (SAR) or B1+rms and a continuous active scan time in the device magnetic resonance imaging (MRI) labelling. Due to the restriction of the labeled SAR, MR sequence parameters may need to be adjusted to reduce RF power, resulting in prolonged scan time. The patient examination duration may be extended by up to 67% when compared to standard protocols. The overall session may be further prolonged due to additional wait time requirements from certain implanted devices, which can result in great inconvenience and extra cost to patients.

2307		RF safety and image quality testing of deep brain stimulation electrodes with 3T MRI
		Gaurav Verma¹, Paul Min², MyungHo In², Jungho Cha³, Akbar Alipour¹, Charlotte Elorette⁴, Lazar Fleysher⁵, Priti Balchandani¹, Helen Mayberg³, and Ki Sueng Choi³
		¹Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ²Radiology, Mayo Clinic, Rochester, MN, United States, ³Center for Advanced Circuit Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ⁴Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ⁵Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
		Radio frequency (RF) safety and image quality testing was performed in the presence of deep brain stimulation (DBS) electrodes using gel acrylamide phantoms and two 3T MRI scanners. Two electrodes, (Abbott and Medtronic) were tested with sequences including GRE, T₁-weighted magnetization-prepared rapid gradient echo (MPRAGE), and T₂-weighted turbo spin-echo (TSE). Safety testing showed low heating when electrodes were aligned along the B₀ field (Z-axis) of the magnet, but higher heating when the electrodes were angled to the main field. Image quality testing showed smaller ferromagnetic susceptibility artifacts when electrode was parallel with B₀ field and normal to transmit field.

2308		Improved compression of SAR matrices by a reformulation of the generalized virtual observation point compression scheme
		Vincent Gras¹ and Nicolas Boulant¹
		¹DRF/Joliot/Neurospin, CEA - Université Paris Saclay, Gif sur Yvette, France
		Parallel transmission to date is the most promising technology to tackle the RF field inhomogeneity problem in MRI at ultra-high field. The Virtual Observation Point compression technique was a cornerstone in the field to reduce drastically the number of SAR matrices to handle in exam supervision and RF pulse design. After its original discovery, it was further improved to boost the compression. This work describes a reformulation of the problem which simplifies substantially the numerical search and allows reducing further the number of matrices by a factor ~5 or more.

2309		Stand-Alone Hardware SAR Monitor based on low cost Electronic Standard Components
		Marcus Prier^1,2, Max Joris Hubmann^1,2, Enrico Pannicke^1,2, and Oliver Speck^1,2
		¹Otto-von-Guericke University, Magdeburg, Germany, ²Research Campus STIMULATE, Magdeburg, Germany
		A low cost, stand-alone RF power monitor was developed that fulfills the requirements given in the standard 60601-2-33 and is based on electrical standard components. It consists of two dual directional couplers, two RMS envelope filters and a microcontroller. A fixed power limit can be programmed or patient dependent power limits can be communicated from a host computer. Evaluation measurements show power measurement and RFPA blanking switching times accuracies with an error less than 1%. A sampling rate of 130kSamples/s indicates usability for relatively short or moderate complex shaped RF waveforms.

2310		Is a Local Tx Coil sufficient for Guidewire Safety in MRI?
		Felipe Godinez^1,2, Greig Scott³, Joseph V Hajnal^1,2, and Shaihan J Malik^1,2
		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, ³Department of Electrical Engineering, Stanford, Stanford, CA, United States
		Imaging guidewires in MRI is known to have heating hazards associated. In this work we show initial data that supports the use of local Tx coils over whole body coils for the safe imaging of standard guidewires with MRI. This was tested in vitro using parallel transmit (PTx) techniques to generate a scenario for a proper comparison between the two coil types. It was found that a local Tx coil produces less heating at the guidewire tip, than a body coil under comparable conditions.

2311		Input Impedance Comparison of MR-Conditional Cardiac Implantable Pulse Generators at the 1.5T MR Frequency of 63.87 MHz
		Jason Meyers¹, David Prutchi¹, and Ramez Shehada²
		¹Impulse Dynamics (USA) Inc., Marlton, NJ, United States, ²Medical Technology Laboratories, La Mirada, CA, United States
		The MR environment poses a tissue heating hazard to patients with cardiac IPGs (implantable pulse generators), such as pacemakers and defibrillators, due to RF currents circulating in the loop formed by the IPG, a transvenous lead, and the tissue. Heating will be limited by the impedance of this loop at the MR frequency (63.87 MHz for 1.5T). The IPG input impedance (a portion of this loop) was measured in six MR-Conditional IPG’s. All have a comparable, low impedance, suggesting that device manufacturers are not intentionally adding impedance and that some interchangeability may be possible without changing RF-induced heating.

2312		Computational simulations of heating in the vicinity of an 8-contact depth EEG electrode: the impact of model simplification
		Hassan B Hawsawi^1,2, Ozlem Ipek^3,4, David W Carmichael^5,6, and Louis Lemieux¹
		¹Clinical and Experimental Epilepsy, University College London, London, United Kingdom, ²Administration of Medical Physics, King Abdullah Medical City, Makkah, Saudi Arabia, ³King’s College London, London, United Kingdom, ⁴CIBM-AIT, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland, ⁵Department of Biomedical Engineering, King’s College London, London, United Kingdom, ⁶Developmental Imaging and Biophysics Section, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
		Electromagnetic (EM) simulations offer the possibility of assessing RF-induced heating around intracranial EEG (icEEG) electrodes across a variety of placement scenarios in a shorter time than experimental phantom-based temperature measurements. However, given the sub-millimetric dimensions of the wires and contacts the range of spatial scales spans many orders of magnitude, leading to high computational demands. In this study, we assessed the effect of model simplification for a typical 8-contact depth EEG electrode on the estimated heating patterns.

2313		Safety Considerations in Neuroimaging of Neonatal and Pediatric Patients Using Portable Low Field MRI
		Mark Smith¹, Harry Hu², Ram Krishnamurthy¹, John Pitts³, and Mai-Lan Ho¹
		¹Nationwide Children's Hospital, Columbus, OH, United States, ²Hyperfine, Dublin, OH, United States, ³Hyperfine, Cleveland, OH, United States
		In 2020, a portable 64mT ultra-low field MRI system designed for point of care bedside use received 510K clearance (Hyperfine, Guilford, CT). Our pediatric institution (Nationwide Children’s Hospital) has acquired one of these systems to meet neuroimaging needs for critically ill NICU or PICU patients who cannot tolerate transport to the MRI department. Prior to scanning patients, safety testing for displacement and heating was conducted on monitoring hardware that will be connected to the patient during the bedside MRI. The monitoring hardware was found safe to stay connected to the patient during the bedside MRI.

2314		Influence of E-Field Homogeneity and Drift for Testing Medical Implants for RF-induced heating at 64MHz according to ASTM-F2182 and ISO/TS 10974
		Finya Ketelsen^1,2, Vincent Hammersen¹, Kevin Kröninger², and Gregor Schaefers^1,3
		¹MRI-STaR - Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany, ²TU Dortmund University, Dortmund, Germany, ³MR:comp GmbH, Testing Services for MR Safety & Compatibility, Gelsenkirchen, Germany
		Medical implants of all kind must be tested for RF-induced heating to determine their MR safety and compatibility. Test conditions concerning E-field homogeneity and E-field drift during assessment time are defined in ISO/TS 10974 and ASTM-F2182. This study evaluates the influence of E-field drift and E-field homogeneity on RF-heating. It shows that both effects can lead to a temperature underestimation. Even for small implants whose volume is in a homogenous area within ±1dB, this underestimation can occur. System instability and implant size and position can further increase the underestimation of RF-induced heating and should be carefully considered.

2315		Parallel-transmit coil dimensions affect SAR sensitivity to motion at 7T.
		Alix Plumley¹, Philip Schmid¹, and Emre Kopanoglu¹
		¹Cardiff University Brain Research Imaging Centre, Cardiff, United Kingdom
		Subject motion in parallel-transmit (pTx) causes channels’ electric field interference patterns to change, influencing SAR distributions. This can cause safety limits to be exceeded when SAR-constrained pulses are designed for one position. Here, we consider effects of pTx coil dimensions on SAR sensitivity to motion by simulating 6 differently-sized coil models, and evaluating SAR at 19 displaced positions. Our results agree with those previously reported for the similar-sized coil, but SAR sensitivity was generally lower for larger coils, and higher for smaller coils, with maximum motion-induced local-SAR increase of 3.8-fold and 1.6-fold for the smallest and largest coil models, respectively.

2316		Safety evaluation with respect to RF-induced heating of a new setup for Transcranial Electric Stimulation during MRI
		Fróði Gregersen^1,2,3,4, Cihan Göksu^2,5, Gregor Schaefers^6,7, Rong Xue^4,8,9, Axel Thielscher^1,2, and Lars Hanson^1,2
		¹Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kgs Lyngby, Denmark, ²Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital, Amager and Hvidovre, Denmark, ³Sino-Danish Center for Education and Research, Aarhus, Denmark, ⁴University of Chinese Academic of Sciences, Beijing, China, ⁵High-Field Magnetic Resonance Center, Max-Planck-Institute for Biological Cybernetic, Tübingen, Germany, ⁶MRI-STaR-Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany, ⁷MR:comp GmbH, MR Safety Testing Laboratory, Gelsenkirchen, Germany, ⁸State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, ⁹Beijing Institute for Brain Disorders, Beijing, China
		Combining transcranial electrical stimulation (TES) with MRI offers various interesting research opportunities, but also introduces safety concerns. Coupling between the RF field and highly conductive TES leads can lead to skin burns. These safety issues are usually mitigated with the use of safety resistors and controlled lead paths that reduce the power absorbed by the leads. However, these methods introduce practical limitations for combined TES/MRI experiments, such as limited stimulation currents and cable stray fields corrupting MR current density imaging. We overcome these limitations by using low-conductivity silicone-rubber as TES leads. Simulations and temperature measurements are used for safety assessment.

2317		Unloaded RF transmit coil B1+ maps do not correlate with SAR hotspots
		Xin Chen¹ and Michael Steckner¹
		¹Canon Medical Research USA Inc., Mayfield Village, OH, United States
		MRI vendors have been asked to provide B1+ contour plots of unloaded whole body transmit coils in order to show technologists/radiographers where not position a patient for SAR hotspot/RF burn avoidance purposes. Two flaws with this strategy are demonstrated by modeling Duke at the abdominal landmark in the centered and off-set position: 1) B1+ maps correlate poorly to SAR hotspots, 2) loaded B1+ maps are significantly different relative to unloaded B1+ maps. Knowledge of the birdcage coil end-ring position in conjunction with spacing pads will improve RF burn safety outcomes.

System & Component Safety

Safety & Multinuclear/Preclinical RF

Engineering/Interventional/Safety

2477		Device and simulation workflow for validating cardiac magneto-stimulation thresholds in porcine models
		Valerie Klein^1,2, Mathias Davids^1,2,3, Donald Straney², Livia Vendramini², Lothar R. Schad¹, Maaike van den Boomen^2,3,4, Christopher Nguyen^2,3,4, Lawrence L. Wald^2,3,5, and Bastien Guerin^2,3
		¹Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany, ²A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ³Harvard Medical School, Boston, MA, United States, ⁴Cardiovascular Research Center, Cardiology Division, Massachusetts General Hospital, Charlestown, MA, United States, ⁵Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States
		We developed a magnetic stimulator to measure cardiac stimulation (CS) thresholds of time-varying magnetic fields in pigs. The stimulator consists of a high-power capacitor bank (C=110 µF) discharging into a pancake coil. We will use the measured thresholds to validate a previously developed CS simulation framework that combines electromagnetic field simulations with electrophysiological models of excitable cardiac fibers. We generate whole-body porcine voxel models from multi-bed MRI Dixon and CINE acquisitions to reproduce the anatomy and posture of the animals in our simulations. Carefully validated CS simulations may eventually be useful in setting cardiac safety limits for MRI gradient applications.

2478		Are interventionalists prone to nerve stimulation during MR interventions? PNS simulation study with posable human body models
		Feng Jia¹, Sebastian Littin¹, Philipp Amrein¹, Maximilian Frederik Russe¹, and Maxim Zaitsev^1,2
		¹Department of Radiology, Medical Physics, University of Freiburg, Faculty of Medicine, Freiburg, Germany, ²High Field MR Center Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
		TODO Simulation of peripheral nerve stimulation of MRI gradient coils for an interventional radiologist.

2479		Electric Field Calculation and PNS Prediction for Head and Body Gradient Coils
		Koray Ertan^1,2, Trevor Wade^3,4, Andrew Alejski⁴, Charles A McKenzie³, Paolo Decuzzi², Brian Rutt¹, and Peter B Roemer⁵
		¹Department of Radiology, Stanford University, Stanford, CA, United States, ²Laboratory of Nanotechnology for Precision Medicine, Italian Institute of Technology, Genoa, Italy, ³Department of Medical Biophysics, Western University, London, ON, Canada, ⁴Robarts Research Institute, Western University, London, ON, Canada, ⁵Roemer Consulting, Lutz, FL, United States
		Computationally efficient methods are presented which allow calculation of switched-gradient-induced electric field distributions on realistically sized body model with uniform interior properties (compatible with regulatory IEC standards). Electric fields were calculated for three classes of gradient coils (asymmetric head, symmetric head and body gradients) using 100-member male and female body model populations; these were then used to estimate population-mean PNS parameters which were validated against experimental PNS measurements, showing high accuracy. Our computationally efficient methods can calculate whole-body E-field distributions in seconds with updates for different gradient designs in tens of milliseconds, providing an important tool for PNS-constrained gradient design.

2480		Peripheral Nerve Stimulation limits with fast narrow and broad-band pulses
		Joseba Alonso^1,2, Daniel Grau^2,3, Juan Pablo Rigla³, Eduardo Pallás^1,2, José Miguel Algarín^1,2, José Borreguero^1,2, Rubén Bosch^1,2, Guillermo Comazzi^1,2, Elena Díaz³, Fernando Galve^1,2, José Manuel González³, Carlos Gramage^1,2, Rubén Pellicer^1,2, Alfonso Ríos³, and José María Benlloch^1,2
		¹Spanish National Research Council (CSIC), Valencia, Spain, ²Universitat Politècnica de València, Valencia, Spain, ³Tesoro Imaging S.L., Valencia, Spain
		We present an apparatus for PNS threshold determination on a subject's limb, capable of narrow and broad-band magnetic excitation with pulse characteristic times down to 40 us. From measurements on 51 volunteers, we observe that PNS limits coincide for sinusoidal and triangular excitations, and are slightly lower for trapezoidal pulses. We measure significant correlations of PNS sensitivity with arm size and body weight, and none with height or gender. We confirm thresholds increase significantly for short trains also in these fast timescales. Finally, we propose our versatile low-cost system for fast offline determination of a subject's limits prior to scanning.

2481		Design and Electric Field Analyses of a Shorter and Wider Asymmetric Gradient Coil for Whole Body MRI Scanners: A Comparison with a Symmetric Design
		Afis Ajala¹, Yihe Hua¹, Desmond Teck Beng Yeo¹, Mark Vermilyea¹, and Thomas Foo¹
		¹GE Global Research, Niskayuna, NY, United States
		A unique approach to providing a more open, less claustrophobic whole-body MRI is presented. A design for an asymmetric gradient coil moves the region of interest (ROI) towards one end of the gradient coil, shortening the gradient coil length from the isocenter to the patient opening. This results in a stepped configuration where the patient-bore diameter outside of the imaging ROI is substantially wider compared to using a conventional symmetric gradient coil design. The stepped patient bore has previously been used in head-only gradient systems where the greater openness has resulted in increased patient comfort and reduced claustrophobia.

2482		Thermal simulations for a high power diffusion weighting MR gradient coil
		Philipp Amrein¹, Feng Jia¹, Sebastian Littin¹, and Maxim Zaitsev¹
		¹Dept.of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany
		In the context of the development of a high power MR diffusion probe for the human breast, a computer model for thermal simulation was created that allows evaluation of different duty cycles and current strengths. The proposed method includes simulating constant effective currents rather than time resolved pulse sequences. This allows reasonable computational effort to analyze the heating effects for a given diffusion weighting sequence on a given gradient system. The simulated results show reasonable agreement with experimental data.

2483		Induced heating of compact cryogen-free superconducting magnet during field-cycling insert coil operation
		Matthew A. McCready¹, William B. Handler¹, and Blaine A. Chronik¹
		¹Physics and Astronomy, Western University, London, ON, Canada
		Delta relaxation enhanced magnetic resonance (dreMR) is a field-shifting quantitative molecular imaging method. The dreMR method is expected to produce higher contrast images at low-fields. Our low-field magnet has a small bore and may interact more strongly with the dreMR system causing a quench. No investigation of induced heating within the bore has been carried out for dreMR. Here, we investigate this interaction with our 0.5T superconducting magnet and find that dreMR pulse sequences do not cause significant heating in the magnet. We therefore state that dreMR is safe to carry out in such systems without quenching the magnet.

2484		Evaluation of a Novel Acoustic Noise Shield for PET-MR
		Chen Lin¹, LeRoy H Stecker¹, Brittany L Benson¹, Craig A Hildestad², Shengzhen Tao¹, and Robert A Pooley¹
		¹Radiology, Mayo Clinic, Jacksonville, FL, United States, ²Mayo Clinic, Jacksonville, FL, United States
		A novel acoustic noise shield constructed of clear acrylic has been developed and evaluated. The results suggest that: 1) it is effective for MR acoustic noise reduction, 2) PET image quality exceeds ACR accreditation testing standards with the proposed acoustic shield in use, showing its compatibility with PET imaging, 3) there is a small impact on PET SUV which can be compensated with attenuation correction, and 4) it does not cause claustrophobia.

2485		Acoustic evaluation of carbon fiber RF shield structure for a 3T head-only imaging system
		Matthew Tarasek¹, Tom Foo¹, Mark Vermilyea¹, Desmond Yeo¹, Isabelle Jansen¹, Eric Budesheim ¹, and Keith Park¹
		¹GE Global Research, Niskayuna, NY, United States
		In this work we evaluate the MRI acoustic changes brought about by modifying the RF shield structure in a head-only (MAGNUS) 3T imaging system. Specifically, we use a standardized acoustic measurement protocol to compare sound pressure levels (SPL) in a fiberglass patient-bore structure to a similar newly developed carbon fiber reinforced polymer (CFRP) structure. Results indicate that a modification of the structural properties of the patient-bore structure properties can provide SPL reduction for MR imaging applications, and is likely due to the different modulus of elasticity between the two materials.

2486		MRSaiFE: towards the real-time prediction of tissue heating in MRI - a feasibility study
		Simone Angela Winkler¹, Elizaveta Motovilova¹, Sayim Gökyar¹, Isabelle Saniour¹, Fraser Robb², and Akshay Chaudhari³
		¹Department of Radiology, Weill Cornell Medicine, New York, NY, United States, ²GE Healthcare, Aurora, OH, United States, ³Stanford University, Stanford, CA, United States
		A crucial safety concern for UHF MRI is the significant RF power deposition in the body in the form of local specific absorption rate (SAR) hotspots, leading to dangerous tissue heating/damage. This work is a proof-of-concept demonstration of an artificial intelligence (AI) based real-time MRI safety prediction software (MRSaiFE) facilitating safe generation of 3T and 7T images by means of accurate local SAR-monitoring at sub-W/kg levels. This feasibility study demonstrates that SAR patterns can be predicted with a root-mean-square error (RMSE) of <11% along with a structural similarity (SSIM) level of >84% for both field strengths.

2487		Motion and Pose Variability of SAR Estimation with Parallel Transmission at 7T
		Amer Ajanovic¹, Joseph V Hajnal^1,2, Raphael Tomi-Tricot^1,3, and Shaihan Malik¹
		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, ³MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom
		Contemporary safety assessment for parallel transmit (pTx) MRI relies on computationally expensive electromagnetic (EM) simulations; hence, safety evaluations rely on the use of small numbers of models. The effect of patient movement inside the coil on patient safety is, therefore, difficult to capture. In this work we compare 'within-scan' variability with the alternative scenario in which a subject’s head is positioned arbitrarily within the coil, but that this position is different to the one used for the SAR estimation model; we refer to this as ‘pose’ variability.

2488		Robustness of pTx safety concepts to varying subjects and subject positions
		Johannes Petzold¹, Bernd Ittermann¹, and Frank Seifert¹
		¹Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
		This simulation study compares two concepts ensuring IEC-compliant SAR values for parallel transmission (pTx) in respect to their robustness against subject- and position-changes: 1) direct SAR assessment (SL) and 2) an amplitude limit for all pTx channels (AL). For the example case of a 3T pTx body coil, SL resulted in ten-fold the allowed SAR in one model for the same excitation vector that obeys IEC limits in another model. For AL, less than twice the SAR was found in this case. AL allows for a lower safety factor, therefore, resulting in a higher mean(B₁⁺) compared to SL.

2489		Radiofrequency safety evaluation and management of the Australian MRI-Linac system
		Mingyan Li¹, Ewald Weber¹, Aurelien Destruel², Feng Liu¹, and Stuart Crozier¹
		¹School of Information Technology and Electrical Engineering, The University of Queensland, Australia, Australia, ²Center for Magnetic Resonance in Biology and Medicine, Aix-Marseille University, MARSEILLE, France
		The Australian MRI-Linac system has a split magnet with wide opening, which offers treatment flexibility with different patient positioning. However, the versatile patient setup and individual physique differences also lead to uncertainty for specific absorption rate (SAR) management. In particular, a standing patient may have body regions close to radiofrequency (RF) coil rungs, which may lead to high local SAR. In this work, numerical simulations were employed to investigate the SAR distribution while a human model was in different treatment positions and thus give safety management suggestions. A standard whole-body RF coil was also simulated as a reference.

2490		Electromagnetic simulation analysis of an RF burn injury case occurred at the elbow-bore wall contact point
		Minghui Tang¹, Kiyoi Okamoto², and Toru Yamamoto¹
		¹Faculty of Health Sciences, Hokkaido University, Sapporo, Japan, ²Graduate School of Health Sciences, Hokkaido University, Sapporo, Japan
		RF burn injuries occasionally occur at the contact points of skin and the bore wall, albeit out of common belief of hazardous loop forming. To investigate the mechanism of the RF burn injury occurred by the bore wall contact, we modeled an elbow-bore wall contact case on an electromagnetic analysis software by using the computable human phantom. The simulated SAR at the contact point varied up to 480% depending on the patient position in a scanner. This tendency was in accordance with the simulated electric field distribution in the scanner which is dominantly determined by the RF transmission coil.

2491		A Novel Specific Absorption Rate Prediction Framework Using Multi-Task Feedback Generative Adversarial Learning: Application to 10.5 T Head MRI
		Jinyoung Kim¹, Alireza Sadeghi-Tarakameh¹, Angel Torrado-Carvajal^2,3, and Yigitcan Eryaman¹
		¹Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, ²Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States, ³Medical Image Analysis and Biometry Laboratory, Universidad Rey Juan Carlos, Madrid, Spain
		In this study, we propose a novel local SAR prediction framework based on deep learning. To this end, we introduce multi-task feedback adversarial learning to simultaneously predict local SAR distribution and its peak SAR value. The proposed model learns a mapping between simulated B1+ magnitude/tissue property maps and local SAR provided by EM simulations. Given query inputs with the properly trained model, the generator produces the local SAR distribution slice by slice, and the local SAR peak estimator predicts the upper bound of local SAR values. Validation results show that the proposed model may allow online subject-specific local SAR prediction.

2492		Realistic model of the 3T Siemens Connectom birdcage coil and its validation
		Mikhail Kozlov¹, Kerrin J. Pine¹, and Nikolaus Weiskopf^1,2
		¹Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ²Felix Bloch Institute for Solid State Physics, Leipzig, Germany
		We devised a numerical model of a 123.2MHz 32-rung high-pass whole-body birdcage coil of the Siemens 3T Connectom scanner. The model was developed based on realistic geometrical data for most of coil elements and a reverse engineering approach. Our simulations suggest that RF exposure at level of 3.2W/kg head SAR may result in higher than 20W/kg of SAR_10g in the Connectom scanner; (ii) B₁+ mapping alone cannot be used for validation of numerical model of whole-body birdcage coil, (iii) developed RF-circuit and 3D-EM co-simulation approach with reverse engineering resulted in a reasonable agreement between simulations and measurements in human subject.

2493		GPU accelerated calculations of the scattered RF-field due to a dielectric update without extensive pre-calculated data.
		Peter Stijnman¹, Bart Steensma¹, Cornelis van den Berg¹, and Alexander Raaijmakers^1,2
		¹Computational Imaging, UMC Utrecht, Utrecht, Netherlands, ²Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
		Previous work showed that the scattered RF-fields created by dielectric pads and medical implants can quickly be calculated. The method requires an extensive offline calculation stage and a lot of memory. We propose an extension to the method that removes these two problems by using a volume integral equation solver. This allows us to do the entire calculation on a GPU for more acceleration. The resulting scattered electric fields have a maximum difference of 3.2% with respect to FDTD, while currently being a 106 times faster. Eventually, we want to use this method for patient-specific implant RF-safety assessment.

2494		RF Safety Assessment of High Permittivity Dielectric Pads - Impact of Material Insulation
		Wyger Brink¹, Rob Remis², and Andrew Webb³
		¹Leiden University Medical Center, Leiden, Netherlands, ²Circuits and Systems, dept. of Microelectronics, Delft University of Technology, Delft, Netherlands, ³C.J. Gorter Center, dept. of Radiology, Leiden University Medical Center, Leiden, Netherlands
		High permittivity dielectric pads are known to be effective for tailoring the RF field and improving image quality in high field MRI systems. Despite the number of studies reporting benign SAR effects, their safety remains a concern and should be evaluated on an application-specific basis using RF simulations. In this work we demonstrate the impact of insulation material on the RF safety of high permittivity pads, using both RF simulations as well as phantom experiments.

2495		Advances in Caterpillar Traps: A Highly Flexible, Distributed System of Toroid Cable Traps
		Ekin Karasan¹, Alison Hammerschmidt¹, Victor Taracila², Fraser Robb², and Michael Lustig¹
		¹University of California, Berkeley, CA, United States, ²GE Healthcare, Coils, Aurora, OH, United States
		Conducting wires within the scanner may interact with the transmit field causing high shield currents and posing safety hazards. Closely spaced RF traps are used to mitigate common-mode currents. However, these bulky and rigid traps hinder the flexibility of the cable. We previously proposed caterpillar traps: a distributed system of smaller, flexible toroids covering the full length of the cable. Their potential to attenuate shield currents while being flexed was demonstrated. This work makes several improvements to the manufacturing process to reduce time and cost and improve usability. Furthermore, we present results from experiments to evaluate their performance and robustness.

2496		LCCC Balun for RF Coil
		Xinqiang Yan^1,2 and John C. Gore^1,2
		¹Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Department of Radiology and Radilogical Science, Vanderbilt University Medical Center, Nashville, TN, United States
		We introduced a novel LCCC lumped-element balun to suppress the unwanted common-mode current in RF coils and RF systems. Unlike the 4-element Lattice balun consisting of two capacitors and two inductors (LCCL), this design has 3 capacitors and only 1 inductor. With fewer inductors (previous lumped-element baluns need at least 2 inductors), this LCCC balun can further be miniaturized and has lower insertion loss.

Multinuclear & Preclinical RF Coils

Safety & Multinuclear/Preclinical RF

Engineering/Interventional/Safety

2497		Signal-to-noise-ratio gain and in vivo application of a 13C cryo-coil for hyperpolarized MRSI
		Luca Nagel¹, Geoffrey J. Topping¹, and Franz Schilling¹
		¹Department of Nuclear Medicine, Technical University of Munich, School of Medicine, Klinikum rechts der Isar, Munich, Germany
		Cryogenically cooled transmit/receive radiofrequency coils (cryocoils) improve the signal-to-noise ratio (SNR) compared to conventional RF coils by minimizing thermal coil noise. The SNR of a cryoprobe, a surface coil at room temperature and a volume coil was assessed using chemical shift imaging of a ¹³C-urea phantom. Using the cryocoil an SNR improvement up to a factor of 10 compared to conventional coils was observed. In addition, a proof-of-concept in vivo experiment using the ¹³C-cryocoil for detection of the metabolic turnover of hyperpolarized ¹³C-pyruvate was successfully performed.

2498		Ultra-Flexible 8-Channel Receive Array for 13C Imaging
		Vitaliy Zhurbenko¹, Juan Diego Sánchez Heredia¹, Wenjun Wang¹, and Jan Henrik Ardenkjær-Larsen¹
		¹Technical University of Denmark, Kgs. Lyngby, Denmark
		Imaging of low-abundance nuclei could benefit from close proximity detecting coils. Close proximity is conveniently achieved using flexible arrays, which conform to the shape of the subject. In this work, a design of an 8-element ultra-flexible array for ¹³C imaging is presented. Each array element includes a low-noise preamplifier with ¹³C/¹H active and passive decoupling, as well as high-power pulse protection circuits. The array is lightweight and easy to handle. The design approach is directly scalable to larger size arrays.

2499		Metamaterial Liner RF Head Coil for 23Na and 1H at 4.7 T
		Adam Maunder¹, Ashwin Iyer², and Nicola De Zanche¹
		¹Oncology, Medical Physics, Cross Cancer Institute, University of Alberta, Edmonton, AB, Canada, ²Electrical and Computer ENgineering, University of Alberta, Edmonton, AB, Canada
		Well-established and emerging methods of ²³Na sodium imaging in the brain benefit from high field strength, but require imaging sequences that are constrained by specific absorption rate (SAR) limits. Additionally, concurrent proton imaging is desirable for complementary anatomical/structural information. Here, we present a novel metamaterial liner-based MR coil for ²³Na/¹H imaging at 4.7 T, consisting of longitudinally-spaced rings that alter the effective electromagnetic properties between the liner and outer RF shield (waveguide boundary). In simulation, the metamaterial liner was found to produce lower local 10g averaged SAR for the same mean transmit field relative to a conventional birdcage coil.

2500		1H, 31P, 23Na, and 13C imaging and spectroscopy with a multi-tunable double-coil assembly
		Viktor Puchnin¹, Viacheslav Ivanov¹, Mikhail Gulyaev², and Mikhail Zubkov¹
		¹Department of Physics and Engineering, ITMO University, Saint-Petersburg, Russian Federation, ²Faculty of Fundamental Medicine, Lomonosov Moscow State University, Moscow, Russian Federation
		The RF-coils of small-animal scanners often limit the range of accessible nuclei to single- or double-nuclear scanning. Here, a multi-tuneable RF-coil design is investigated. The design comprises a butterfly-type RF-coil for ¹H, and a multi-tuneable coil for X-nucleus imaging. The coil assembly is tested in a 7 T scanner. ¹H and X-nucleus field maps show good matching between the simulation and experiment. Imaging and spectroscopy experiments provide well-resolved images as well as distinctive spectral peaks corresponding to the phantom compounds. The presented imaging method with single coil assembly is considered a promising expansion of heteronuclear imaging.

2501		SNR and B1+ Field Homogeneity of a Koch Fractal Geometry RF Surface Coil for 23Na-MRI
		Cameron Nowikow¹, Paul Polak¹, Norman B. Konyer², Natalia Nikolova³, and Michael D. Noseworthy^1,2,3
		¹School of Biomedical Engineering, McMaster University, Hamilton, ON, Canada, ²Imaging Research Centre, St. Joseph's Healthcare, Hamilton, ON, Canada, ³Electrical and Computer Engineering, McMaster University, Hamilton, ON, Canada
		There is an intrinsic lack of SNR in ²³Na-MRI images compared to that of proton-based MRI. It is possible that RF coil geometry can affect the acquired images' SNR. This abstract is an investigation into the B₁⁺ field characteristics of a Koch snowflake fractal RF surface coil to see if the produced field is more homogeneous than that of a standard circular surface coil which could lead to higher SNR in the resultant ²³Na images. It was found that the circular geometry produced a more homogeneous field, along with higher SNR than the fractal coil.

2502		Towards a cryogenic RF coil array for 13C human head imaging: first experience
		Wenjun Wang¹, Juan Diego Sánchez Heredia², Vitaliy Zhurbenko¹, 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
		A cryogenic coil and a dedicated cryostat for ¹³C human head imaging is developed. A 1.90-fold SNR enhancement over a room temperature coil is observed experimentally. To verify the retention of SNR enhancement in arrays, a 4-channel cryogenic coil array and another cryostat are also developed. The superior performance to a room-temperature array is confirmed experimentally.

2503		Quantitative Comparison of 31P MRS Imaging Performances between 7T and 10.5T Human Scanners Using a Loop-dipole 31P-1H Probe
		Xin Li¹, Hannes M. Wiesner¹, Matt Waks¹, Xiao-Hong Zhu¹, and Wei Chen¹
		¹Center for magnetic Resonance Research (CMRR), Department of Radiology, University of Minnesota, Minneapolis, MN, United States
		In vivo ³¹P MRS imaging (MRSI) is important for studying cerebral energy metabolism, intracellular NAD and redox ratio. However, it is challenging to achieve high spatiotemporal resolution owing to limited ³¹P sensitivity and low phosphorus metabolites concentration. We had demonstrated that ultrahigh field (UHF) could significantly improve the ³¹P-MRS sensitivity and spectral resolution. In this study, we designed and constructed a loop-dipole ³¹P-¹H probe, which could operate at 7T and 10.5T for quantitative comparison of ³¹P MRSI signal-to-noise ratio (SNR) between the two fields. We found that the apparent SNR at 10.5T was significantly higher than that of 7T.

2504		A nested dual-tuned proton-sodium loop-array transceiver coil on a 9.4T whole-body MRI system
		Zhe Wang¹, Fangrong Zong², Cheng Fang¹, Wenhui Yang^3,4, Shasha Yue¹, Yan Hou², Zehui Li², Tianyu Xie², Kun Zhang², Yan Zhuo^1,4,5, Xiaohong Joe Zhou⁶, Xiaoliang Zhang⁷, and Rong Xue^1,4,8
		¹State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, ²Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, ³Institute of Electrical Engineering Chinese Academy of Sciences, Beijing, China, ⁴University of Chinese Academy of Sciences, Beijing, China, ⁵CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Beijing, China, ⁶Center for MR Research and Departments of Radiology, Neurosurgery and Bioengineering, University of Illinois at Chicago, Chicago, IL, United States, ⁷Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States, ⁸Beijing Institute of Brain Disorders, Beijing, China
		In this study, a nested dual-tuned proton-sodium multi-channel loop-array transceiver coil was designed and constructed for 9.4T MRI, which could provide images for both proton and sodium at the same location. This coil adopts nested structure, which contains 8-channel transceiver loop elements respectively, and each loop is equipped with an independent transmit/receive circuit. The coil array was simulated for B1 field distribution and was further tested on a 9.4T whole-body MRI platform with home-built spectrometer. Proton and sodium images on a water phantom were successfully collected on this system with high quality.

2505		Flexible 32-Channel 13C MRI Head Array: An EEG-Lookalike Design Approach
		Juan Diego Sánchez Heredia¹, Wenjun Wang^1,2, 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
		We propose a design concept for flexible human head coil arrays applicable to a wide frequency range. Electrically, the design relies on high decoupling obtained through a controlled high mismatched connection to the low-impedance preamplifiers. Mechanically, the array is built into a neoprene EEG cap, and made of regular-copper flexible wire. The array layout is designed to have an axis to stretch along, therefore allowing tight fit to a variety of human-head sizes. A 32-channel prototype for ¹³C at 3T (32.1 MHz) is presented and evaluated, showing SNR performance superior to a ¹³C-dedicated volume coil.

2506		9.4 T Double-Tuned 13C/1H Human Head Array Using a Combination of Surface Loops and Dipole Antennas.
		Nikolai Avdievich¹, Georgiy Solomakha², Loreen Ruhm¹, Anke Henning^1,3, and Klaus Scheffler¹
		¹High-field Magnetic Resonance, Max Planck Institute for Bilogical Cybernetics, Tübingen, Germany, ²Physics and Engineering, ITMO University, St. Petersburg, Russian Federation, ³Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States
		Dipole antennas have been successfully utilized at ultra-high fields (UHF, >7 T) for human body and head imaging. Combining X-nuclei surface loops and ¹H dipoles can substantially simplify the design of a double-tuned UHF human head coil. In this work, we developed and constructed a novel ¹³C/¹H human head 9.4 T array coil consisting of eight ¹³C surface loops and eight ¹H folded-end dipoles surrounding the head. We showed that coupling between loops and dipoles can be minimized by placing four ¹H traps into each ¹³C loop. The new coil demonstrated an improved ¹H longitudinal coverage and reasonable Tx efficiency.

2507		Analysis of common-mode rejection ability and Insertion Loss of Dual band Lattice Balun with non-ideal components
		Yue Zhu^1,2 and Xinqiang Yan^1,2
		¹Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States
		A dual band Lattice balun was proposed previously, which holds the promise of removing common mode current for both frequencies in dual-tuned MRI coils with a single interfacing unit. However, the previously fabricated unit had a considerable insertion loss at the proton Larmor frequency. In this work, we analyzed how each lumped element will affect this device's performance and optimized the circuit performance based on the analysis.

2508		Interleaved nine-leg birdcages for simultaneous geometric decoupling from a double tuned planar array
		Joseph Busher¹, Chenhao Sun², Travis Carrell¹, Edith Valle², Steven M. Wright^1,2, and Mary McDougall^1,2
		¹Biomedical Engineering, Texas A&M University, College Station, TX, United States, ²Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States
		This work describes two interleaved nine-leg linear birdcages for geometric decoupling from a double-tuned planar array for 1H and 23Na at 4.7T. An asymmetric design was chosen to create aligned fields to simultaneously decouple the receive array from the two transmit birdcages. This straightforward design provides sufficient decoupling from coils in all six positions in the final array configuration and enables multinuclear multichannel imaging experiments.

2509		Flexible 8-Channel Array for Hyperpolarized 13C at 3T (32.1 MHz), with Nearly Identical 23Na (33.8 MHz) Sensitivity Profiles
		Juan Diego Sánchez Heredia¹, Wenjun Wang^1,2, James T. Grist^3,4,5, Esben Søvsø Szocska Hansen⁶, Christoffer Laustsen⁶, 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, ³Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom, ⁴Oxford Centre for Magnetic Resonance, University of Oxford, Oxford, United Kingdom, ⁵Department of Radiology, The Churchill Hospital, Oxford University Hospitals NHS Trust, Oxford, United Kingdom, ⁶The MR Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
		We describe the design of a flexible coil array tuned optimally for ¹³C MRI at 3T (32.1 MHz), but with the coil coupling coefficients matched to be nearly identical at the ¹³C and ²³Na (33.8 MHz) frequencies. In this way, the array provides the means to obtain accurate sensitivity profiles for hyperpolarized ¹³C imaging from the high ²³Na naturally present in biological tissue. We show the feasibility of this approach, and compare the performance to other ¹³C coils, showing that the ¹³C SNR provided by this array is not compromised despite the modification to equalize the ¹³C and ²³Na profiles.

2510		Increased B1+ efficiency of a dipole antenna compared to a loop coil for 31P-MRS at 7T: simulations and cardiac MRSI data
		Jabrane Karkouri¹, Saba Shirvani¹, Tiger Zhang¹, Dennis Klomp², Martijn Lunenburg³, Ladislav Valkovic⁴, and Christopher T. Rodgers¹
		¹Wolfson Brain Imaging Center, University of Cambridge, Cambridge, United Kingdom, ²Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ³Tesla Dynamic Coils, Zaltbommel, Netherlands, ⁴Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, United Kingdom
		We evaluated the performance of two RF coil configurations for ultra-high field (7T) 31P-MRS applications in the body. We tested: (A) a dipole Tx/Rx + loop Rx coil vs (B) a quadrature dual-loop Tx/Rx coil. We assessed their relative performance by EM modelling simulations and through phantom and in vivo cardiac scans. Both simulations and experimental verifications indicate that there is notable improvement in terms of B1+ efficiency for the dipole+loop combination compared to quadrature loops. We extrapolate these preliminary findings to predict the performance of the dipole+loop combination if driven at 35kW total like our previous whole-body birdcage coil.

2511		Optimized Single-loop Coil with 3D-shaped Design for Simultaneous fMRI and Optical Imaging in Rodent
		Wen-Ju Pan¹, Lei Zhou¹, Gloria Perrin Clavijo¹, Vahid Khalilzad Sharghi¹, and Shella Keilholz¹
		¹Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA, United States
		Single loop coil was optimized in 3D shape to fitting rodent bran geometry and designed in slim and large center opening to meet the requirement of simultaneous fMRI and optical imaging. Relative to conventional 2D flat loop, the proposed 3D design may allow setting a loop coil closer to rat cerebral hemispheres and save more overhead space for optical imaging configuration than a 2D flat coil while keeping B1 perpendicular to B0. Our 3D-shape modification exhibited significant improvement in overall SNR and signal homogeneity especially in cortical areas and center brain in T2-weighted images, EPI and field maps.

2512		Inductively coupled small-diameter volume coils insertable to the knee coil at 7T for MR microscopy
		Tomohisa Okada¹, Shinya Handa², Bill Ding², Shin-ichi Urayama¹, Koji Fujimoto¹, Atsushi Shima³, Takashi Ayaki⁴, Nobukatsu Sawamoto³, Ryosuke Takahashi⁴, Hirotaka Onoe¹, Tadashi Isa¹, and Labros Petropoulos²
		¹Human Brain Research Center, Kyoto University, Kyoto, Japan, ²Quality Electrodynamics, Mayfield Village, OH, United States, ³Department of Human Health Sciences, Kyoto University, Kyoto, Japan, ⁴Department of Neurology, Kyoto University, Kyoto, Japan
		MR imaging is frequently correlated to histopathology of specimen, and their high-resolution imaging is required. However, it is not usually feasible using the whole-body human MR scanner. We implemented inductively coupled small diameter coils insertable to the knee coil at 7T without modification of the coil interface. Up to isotropic 50 μm imaging was successfully conducted, and fine details of the specimen could be visualized using the same sequence for in vivo scans. The proposed coils are easy to use and will facilitate investigation of image-histopathology correlation.

2513		A Simple, Multi-purpose Coil for Improved Mouse Brain Image Quality and Coverage at 3-T MRI
		Kuan-Hung Cho¹, Po-Hsun He¹, Hsuan-Han Chiang¹, Ming-Jye Chen¹, Ezequiel Farrher², Nadim Jon Shah^2,3, Chang-Hoon Choi², and Li-Wei Kuo^1,4
		¹Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Miaoli County, Taiwan, ²Institute of Neuroscience and Medicine – 4, Forschungszentrum Juelich, Juelich, Germany, ³Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany, ⁴Institute of Medical Device and Imaging, National Taiwan University College of Medicine, Taipei, Taiwan
		For mouse brain imaging, determining the size of a loop coil is a trade-off between SNR and imaging coverage. Here, we propose a multi-purpose coil arrangement incorporating a small loop coil and a position-adjustable add-on saddle coil to enhance the imaging coverage of anatomical images and improve the SNR in the regions distant to the surface coil. The result shows the imaging coverage can be adjustable for targeting different brain regions and demonstrated this design concept in mouse brain imaging experiments.

2514		Development of a multi-turn double helix dipole coil for magnetic resonance microimaging of chemically-fixed human embryos at 7T.
		Yuto Murakami¹ and Yasuhiko Terada¹
		¹University of Tsukuba, Tsukuba, Japan
		A double helix dipole (DHD) coil, consisting of two tilted solenoid coils, exhibits the high signal-to-noise ratio (SNR) close to that of an equivalent solenoid whose SNR is almost three times larger than a saddle coil. However, its application to high-field MRI is challenging because of the high inductance. Here, we proposed a new DHD coil design with division capacitors that enables high-field MRI application. As proof-of-concept, we designed a 6-turn DHD coil for MR microimaging of a chemically-fixed human embryo specimen at 7T, and showed that the proposed DHD has nearly twice the SNR of an equivalent saddle coil.

2515		Wirelessly controlled stand-alone automatic RF tuning and matching system for preclinical imaging at 7T
		Sri Kirthi Kandala¹ and SungMin Sohn²
		¹Biomedical Engineering, Arizona State Universirty, Tempe, AZ, United States, ²Biomedical engineering, Arizona State University, Tempe, AZ, United States
		Impedance matching of RF coils during MR imaging is crucial to improve SNR and would enhance power transfer efficiency for transmit coil reducing wastage of RF power. This work focuses on presenting a stand-alone system with wireless Automatic Tuning and Matching system (ATM) for transmit (Tx)-only and receive (Rx)-only coils separately. We present separate Tx-only and Rx-only coils with high power and low power ATMs respectively along with a self-triggering circuit for Rx coil decoupling while high power Tx signal is active.

2516		Imaging performance of a multi-channel non-human primate coil
		Daniel Papp¹, Urs Schüffelgen², Mo Shahdloo², Sebastian W Rieger^1,3, Aaron T Hess⁴, Matthew Rushworth², and Stuart Clare¹
		¹Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom, ²Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom, ³Wellcome Centre for Integrative Neuroimaging, OHBA, Department of Psychiatry, University of Oxford, Oxford, United Kingdom, ⁴British Heart Foundation Centre of Research Excellence, Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom
		A 15-channel array coil has been developed for our centre by a coil manufacturer for the purposes of awake behaving macaque fMRI. Here, we evaluated the imaging performance in vivo and on phantoms. Compared to a 4 channel flexible coil, we found significant improvements in SNR and tSNR both in vivo and in phantom studies. Furthermore, we demonstrate the feasibility of multiband and in-plane accelerated acquisitions, up to a multiband factor of 6 with in-plane acceleration of 2.

Hot-Wired Systems: Gradients & Magnets

Systems Engineering I

Engineering/Interventional/Safety

3085		Gradient Characterization for High Performance Gradients
		Nastaren Abad¹, Afis Ajala¹, Yihe Hua¹, and Tom K.F Foo¹
		¹General Electric Global Research, Niskayuna, NY, United States
		Impulse response function (IRF) harvesting is a powerful technique for gradient characterization. In this study a field monitoring system was utilized to characterize a head-only, high-performance gradient coil (MAGNUS), enabling expansion of the spatial response pattern into higher order spherical harmonics. The predictive power of IRF-estimated waveforms and field evolution is demonstrated by comparing to nominal and active field monitored approaches for arbitrary gradient waveforms. The calculated modulation function indicated good correspondence for arbitrary waveforms and k-space trajectories varying with slew rate, amplitudes and number of interleaves.

3086		Measuring the Gradient Impulse Response Function (GIRF) for UTE Imaging on an MR-Linac
		Rosie Goodburn¹, Tom Bruijnen², Wajiha Bano¹, Uwe Oelfke¹, and Andreas Wetscherek¹
		¹Radiotherapy and Imaging, The Institute of Cancer Research, London, United Kingdom, ²Department of Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands
		Synthetic CT (sCT) is a key component of adaptive MR-guided radiotherapy. Generation of thoracic sCT is challenging and benefits from ultrashort echo-time (UTE) imaging that provides contrast in short-T2* tissues such as bone and lung. However, UTE imaging is susceptible to artifacts caused by eddy currents and gradient delays. In this work, we measured the gradient impulse response function (GIRF) of an MR-Linac with standard scanner hardware and used it to retrospectively correct k-space trajectories. Images reconstructed with GIRF and gradient-delay corrected trajectories exhibited higher image quality, including reduced halo artifacts, blurring, destructive phase artifacts, and improved uniformity and contrast.

3087		Phantom-based high-resolution measurement of the gradient system transfer function
		Hannah Scholten¹, Manuel Stich², and Herbert Köstler¹
		¹Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany, ²Siemens Healthcare, Erlangen, Germany
		The gradient system transfer function (GSTF) constitutes a comprehensive tool for correcting k-space trajectory distortions due to gradient infidelities. We developed a new phantom-based measurement approach that allows determining the GSTF with a high frequency resolution without relying on long readout durations. Our first results include self- and B₀ cross-terms with high SNR and resolutions below 10 Hz, resolving the true width of several resonances. The high resolution enables us to capture long-lasting eddy current effects, which is especially promising for the application of GSTF-based correction methods in, for example, diffusion-weighted imaging.

3088		Calibration of Concomitant Field Compensation using Phase Contrast MRI
		Thomas K.F. Foo¹, Louis Frigo², Myung-Ho In³, Nastaren Abad¹, Vincent B Ho⁴, and Matt A Bernstein³
		¹GE Research, Niskayuna, NY, United States, ²GE Healthcare, Waukesha, WI, United States, ³Mayo Clinic, Rochester, MN, United States, ⁴Uniformed Services University of the Health Sciences, Bethesda, MD, United States
		A phase contrast pulse sequence was modified to use a single-sided bipolar encoding to calibrate the transverse gradient offsets for asymmetric gradient coils. The phase difference approach cancels the concomitant gradient field effects from all gradient waveforms except for the bipolar gradient waveforms. By fitting the measured phase offset in the phase difference images to the applied bipolar gradient amplitudes, the gradient offset value can be calculated. This was used for pre-emphasis compensation for the zeroth and first order concomitant gradient fields.

3089		Direct Comparison of Gradient Modulation Transfer Functions and Acoustic Noise Spectra of the same MRI at High- (3T) and Lower-Field (0.75T)
		Hannes Dillinger¹, Sebastian Kozerke¹, and Christian Guenthner¹
		¹Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
		In this work, gradient fidelity is compared between high-field (3T) and lower-field (0.75T) configurations on the same MRI system by measuring the Gradient Modulation Transfer Function (GMTF) and audio noise spectra. Results demonstrate that at lower field mechanical resonances are reduced, leading to improved gradient fidelity and reduction of audio noise levels of up to 70%. Furthermore, it is shown that spectral peaks in the audio spectrum can be related to resonances in the GMTF, which suggests mechanical resonances can be identified using the audio spectrum.

3090		PSF-based reconstruction for removal of artifacts caused by misalignment between a silent gradient insert and the body gradients
		Edwin Versteeg¹, Dennis W.J. Klomp¹, and Jeroen C.W. Siero^1,2
		¹Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ²Spinoza centre for neuroimaging Amsterdam, Amsterdam, Netherlands
		A silent gradient axis driven at 20 kHz can reduce sound in MR-sequences. This silent gradient axis consists of a separate coil that is positioned on the patient table and operated in synergy with the whole-body gradients. The positioning of this coil with respect to the whole-body gradients is prone to operator errors which leads to image artifacts. In this work, we show that this misalignment can be characterized and corrected by measuring the point spread function (PSF) of the silent gradient axis. Using this method, a significant reduction in ghosting artifacts was observed in phantom experiments.

3091		Eddy current correction for field probes mounted in a head coil
		Jennifer Nussbaum¹, Maria Engel¹, and Klaas Paul Pruessmann¹
		¹Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
		Concurrent acquisition of dynamic fields has become a prominent way to correct for field imperfections. However, when using field probes in close proximity to a head coil, the field measurement can be corrupted by eddy currents on the head coil that are induced by the gradient fields. In this work, we provide a one-time calibration solution to correct for this issue.

3092		Design and Implementation of High Switching Frequency Gradient Power Amplifier Using eGaN Devices
		Soheil Taraghinia¹, Volkan Acikel², Reza Babaloo^1,3, and Ergin Atalar^1,3
		¹UMRAM, Bilkent University, Ankara, Turkey, ²Aselsan A.S., Ankara, Turkey, ³Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
		In this work, a switching H-bridge gradient power amplifier utilizing eGaN devices is implemented. A single-stage 150 V/ 50 A full-bridge GPA for an insert gradient array system at 1 MHz effective switching frequency is fabricated and tested. Pulse width modulation signals are generated digitally using a Virtex 7 family FPGA board. A single-stage LC low pass filter is designed to attenuate the ripple current.

3093		Droop compensation of gradient current waveforms in gradient array systems
		Reza Babaloo^1,2, Soheil Taraghinia², and Ergin Atalar^1,2
		¹Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, ²National Magnetic Resonance Research Center (UMRAM), Ankara, Turkey
		Providing accurate gradient currents is challenging due to the nonlinearity of the gradient system arising from gradient power amplifiers and power supply stages which causes droop in the output currents. This work introduces a nonlinear model for the gradient array system by using the state-space averaging technique and the nonlinear inversion of the model compensates for droop. The feasibility of the method is depicted by simulation and experimental results. The proposed method can provide desired currents by lower voltages which results in minimizing the needed power. It is also possible to use small capacitors to lower the cost of system.

3094		Fast and quiet MPRAGE using a silent gradient axis at 7T – subject experience and qualitative image assessment
		Sarah M Jacobs¹, Edwin Versteeg¹, Leonie NC Visser², Anja G van der Kolk^1,3, Dennis WJ Klomp¹, and Jeroen CW Siero^1,4
		¹Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, Netherlands, ²Alzheimer Center Amsterdam, Department of Neurology, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, Amsterdam UMC, Amsterdam, Netherlands, ³Department of Radiology, the Netherlands Cancer Institute, Amsterdam, Netherlands, ⁴Spinoza Centre for Neuroimaging Amsterdam, Amsterdam, Netherlands
		Acoustic noise can negatively impact patients from anxiety and communication problems to transient and permanent hearing loss. In this pilot study we used a silent gradient axis that is switched at the inaudible frequency of 20 kHz with a silent readout module implemented in an MPRAGE sequence, and investigated subject experience and image quality of fast and quiet anatomical brain imaging at 7T. Here we show preliminary evidence that our silent gradient axis with silent readout module incorporated into a T₁-weighted MPRAGE sequence is perceived more quiet and positive and delivers images of largely acceptable quality.

3095		Gradient induced electric field within a shoulder cut-out gradient coil built for head and neck imaging.
		Arjama A Halder^1,2, Eric J Lessard^1,2, William B Handler¹, and Blaine A Chronik^1,2
		¹xMR Labs, Physics and Astronomy, London, ON, Canada, ²Medical Biophysics, Western University, London, ON, Canada
		This abstract aims to investigate the electromagnetic environment within a high-performance shoulder cut-out gradient coil designed to be used as a part of an all-in-one platform for head and neck imaging applications. The results achieved in this abstract and future measurements that will be performed with this coil will allow the quantification for gradient induced electric field effects experienced by patients and ensure that the coil is within the expected PNS limits.

3096		Approaching order of magnitude increase of gradient strength: Non-linear breast gradient coil for diffusion encoding
		Sebastian Littin¹, Tristan A. Kuder², Feng Jia¹, Arthur Magill², Philipp Amrein¹, Frederik B. Laun³, Sebastian Bicklehaupt⁴, Mathias Davids^5,6,7, Valerie Klein^5,7, Mark E. Ladd², and Maxim Zaitsev^1,8
		¹Department of Radiology, Medical Physics, University Freiburg, Faculty of Medicin, Freiburg, Germany, ²Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany, ³Department of Radiology, MR Physics, University Medical Center Erlangen, Erlangen, Germany, ⁴Department of Radiology, University Medical Center Erlangen, Erlangen, Germany, ⁵Department of Radiology, A. A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ⁶Harvard Medical School, Boston, MA, United States, ⁷Computer Assisted Clinical Medicine, Heidelberg University, Medical Faculty Mannheim, Heidelberg, Germany, ⁸High Field MR Center Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
		Local gradient coils allow for enhanced performance in terms of both gradient amplitude and switching rate. We recently presented the concept of a single channel non-linear breast gradient coil. Here we show results of the characterization, safety assessment and initial diffusion encoded images from phantom experiments of the prototype coil. Is an order of magnitude increase of gradient strength for diffusion weighting feasible using local gradient coils?

3097		Towards a More Power Efficient Two-Channel Biplanar Z-Gradient Coil Design Using Target Field Method
		Haile Baye Kassahun¹, Sadeq S Alsharafi¹, Ahmed M Badawi¹, and AbdEl-Monem M El-Sharkawy¹
		¹Systems and Biomedical Engineering, Cairo University, Cairo, Egypt
		A two-channel biplanar Z-gradient coil design is introduced by dividing the conventional coil surface into two sections radially. The corresponding lower and upper sections are driven by the same current strength but in opposite directions. Coils were designed using the Fourier series expansion (target field) method. For the same target field, the dissipated power of the two-channel biplanar Z-gradient coil was lower than that of the conventional coil (with corresponding dimensions) by at least 25% thereby reducing the ohmic losses. In the future, the benefit of using multi-channel bi-planar gradient coils may be further investigated.

3098		Design of Biplanar Matrix Z2 Nonlinear Gradient Coil with An Open Structure for O-Space imaging
		Congcong Liu^1,2, Shi Su¹, Ye Li^1,2, Xin Liu^1,2, Hairong Zheng^1,2, Dong Liang^1,2,3, and Haifeng Wang^1,2
		¹Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, ²Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Shenzhen, China, ³Research Center for Medical AI, Shenzhen Institute of Advanced Technology,Chinese Academy of Sciences, Shenzhen, China
		In this work, a novel biplanar matrix Z2 nonlinear gradient coil with an open structure has been designed, which could be employed in open spatial low-field MRI system, and an efficient encoding strategy for O-Space imaging was proposed in combination with the proposed biplanar matrix nonlinear gradient coil, which has the potential to shift the center placements (CP’s) in nonlinear gradient imaging without an external linear gradient field. The biplanar Z2 encoding field generated by a nonlinear gradient element consisting of curve segments was optimized and implemented to show the feasibility of this proposed biplanar matrix coil and encoding approach.

3099		MRI Hybrid Gradient Coil Equipped with a Programmable Z-Array and Conventional X- and Y- Elements
		Manouchehr Takrimi¹ and Ergin Atalar^1,2
		¹UMRAM, Bilkent University, Ankara, Turkey, ²Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
		A novel hybrid gradient coil consisting of two conventional actively shielded x/y gradient coils and a programmable active-shield z-gradient array coil is introduced and simulated. The proposed hybrid gradient coil can dynamically provide the required magnetic profile based on diverse applications in MRI. This is achieved by using a set of independent power amplifiers that feed the conventional coils and the array elements. To show the flexibility, three magnetic profiles are simulated: (a) a conventional profile; (b) a profile with twice z-gradient intensity and a shifted FOV; (c) a profile with quadruple z-gradient intensity when the active-shield is reverse fed.

3100		Mechanical Tilt-Induced Gradient Fields for Low-Field Spokes-and-Hub Permanent Magnet MR Imagers
		Irene Kuang¹, Jason Stockmann^2,3, Elfar Adalsteinsson^1,4, and Jacob White¹
		¹Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, ²A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ³Harvard Medical School, Boston, MA, United States, ⁴Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States
		As recently demonstrated by Cooley et al., for Halbach-array based permanent-magnet MR imagers, time-varying encoding fields can be generated mechanically, by rotating the entire array. In this paper we show that in spokes-and-hub based permanent magnet imagers, time-varying encoding fields can also be generated mechanically, but with much smaller motions. In particular, we show that a quarter-degree magnet tilt, along an easily precessed axis, can produce a spatially-discriminating field gradient. We demonstrate the spatial discrimation using both simulation and measurements from our recently-presented prototype imager.

3101		Systematic, Linear Algebra-based Dimensional Analysis of Gradient Inductance Scaling with Coil Radius
		Matt A Bernstein¹ and Seung-Kyun Lee²
		¹Radiology, Mayo Clinic, Rochester, MN, United States, ²Biomedical Engineering, Sungkyunkwan University, Suwon, Korea, Republic of
		Applying systematic dimensional analysis based linear algebraic methods, we derive the important scaling relation for MR gradient design: gradient coil inductance L scales as the square gradient efficiency (measured in T/m/A) and the fifth power of radius. The inclusion of "turns" as a unit in the dimensional matrix produces the result uniquely, greatly simplifying the analysis.

3102		Acceleration of magnetic field calculation of permanent magnet arrays for their optimizations
		Ting-Ou Liang¹, Yi-Dan Chen², Shao Ying Huang², and Erping Li¹
		¹Zhejiang University, Hangzhou, China, ²Singapore University of Technology and Design, Singapore, Singapore
		Two current-model-based approaches are presented to accelerate the calculation of the magnetic field of permanent-magnet-array(PMA) that consists of magnet blocks. It enables a speedy convergence of optimization of a PMA design that is a key component of the popular body-part-dedicated portable MRI in the recent years. This method can be extended to magnet of other shapes. Both Halbach(60blocks) and sparse Inward-Outward ring-pair-PMA(1,200 blocks) are used as examples to demonstrate the speed and accuracy of the algorithm. The best acceleration is 78.92% and 77.94%calculation-time reduction compared to the conventional nested for-loops, and 99.81% and 99.91%reduction compared to FEM-based commercial software.

3103		Design and Development of a Hybrid Helmholtz Coil System for Production of Low Magnetic Field System (up to 7 mT)
		Yenal Gokpek¹ and Ozkan Doganay¹
		¹Institute of Health Sciences, Ege University, IZMIR, Turkey
		In this study, the design and construction of a hybrid Helmholtz coil system and numerical modelling were investigated for production of homogeneous magnetic field over a volume of interest that consist of cylindrical geometry (h=700mm, r=90mm). The 4‑coil system was constructed and tested by two commercially available low power DC power supplies. The magnetic field created by the 4‑coil system was found to be B=2.5182±0.0035mT over the volume of interest. We found that the simulated and measured magnetic fields are in good agreement (R=0.9759, p<0.05).

3104		D-T2 Distribution Obtained Using CPMG-only Sequence Compared with Traditional SE-CPMG Sequence on the Single-sided NMR Device
		Ziyi Pan¹, Jieying Zhang¹, Hai Luo², Weiqian Wang², Xiao Chen², Ziyue Wu², and Hua Guo¹
		¹Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, ²Marvel Stone Healthcare, Wuxi, Jiangsu, China
		Two-dimension (2D) diffusion-relaxation (D-T₂) correlation measured by a low-cost, portable single-sided NMR system can separate fat and water in biological tissues (for example for liver steatosis detection). Diffusion-editing CPMG sequence is commonly used for such measurement. Recently, a novel approach is proposed to measure the D-T₂ correlation using the simplest CPMG-only sequence. The CPMG-only sequence is less sensitive to motion, and can extend to systems with more imperfect magnetic and radiofrequency fields. This work compares the proposed CPMG-only sequence with the traditional diffusion-editing SE-CPMG sequence. Results show the SE-CPMG and CPMG-only sequences can achieve comparable performance on water-fat separation.

New Shim Systems & Other Advanced MR Engineering

Systems Engineering I

Engineering/Interventional/Safety

3105		In-vivo B0 shimming of the liver using a local array of shim coils in combination with 2nd order spherical harmonics at 7T
		Lieke van den Wildenberg¹, Quincy van Houtum¹, Wybe van der Kemp¹, Catalina Arteaga de Castro¹, Alex Bhogal¹, Paul Chang², Sahar Nassirpour², and Dennis Klomp¹
		¹Radiology Department, UMC Utrecht, Utrecht, Netherlands, ²MR Shim GmbH, Reutlingen, Germany
		Maximizing shim performance, particularly for larger organs such as the liver, is crucial at ultra-high field MRI due to the increased sensitivity to B₀ field inhomogeneity. The conventional shimming in most MRI systems at ultra-high field, provides insufficient correction. However, by combining the available 2^ndorder spherical harmonic fields with an external array of 16 local shim coils, the magnetic field homogeneity in the liver is improved by as much as 44%.

3106		“RF transparent” local B0 shim coil
		Xinqiang Yan^1,2
		¹Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Department of Radiology and Radilogical Science, Vanderbilt University Medical Center, Nashville, TN, United States
		Multiple coils shimming technology has been demonstrated as a promising approach to reduce the B₀ inhomogeneity in MRI. However, strong coupling arises when local DC coils are placed close to the imaging area and RF coils. To solve this problem, we proposed a novel local DC shim coil that has little effect on the RF coils, which we called "RF transparent" DC coil. This concept was validated by EM simulation, bench test, and MR experiments. The RF transparent concept will bring much more freedoms to DC coil design (such as many turn and irregular shaped).

3107		Shim Coils Tailored for Correction of B0 Inhomogeneity in the Human Brain (SCOTCH) at Ultra High Field
		Bruno Pinho-Meneses¹, Jason Stockmann^2,3, Edouard Chazel¹, Paul-François Gapais¹, Eric Giacomini¹, Franck Mauconduit¹, Alexandre Vignaud¹, Michel Luong⁴, and Alexis Amadon¹
		¹Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, ²Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ³Harvard Medical School, Boston, MA, United States, ⁴Université Paris-Saclay, CEA, Institut de Recherche sur les Lois Fondamentales de l'Univers, Gif-sur-Yvette, France
		A Singular Value Decomposition based Multi-Coil Array for B₀ shimming of the human brain was designed from a database of 100 δB₀ fieldmaps. An optimized 2-layer 36-channel MCA design was obtained and constructed. The system was characterized and measured fieldmaps were used for comparison to expected performance from ideal simulated fields. The static whole-brain and dynamic slice-wise shimming was validated in-vivo and assessed with GRE and EPI acquisitions at 7 Tesla.

3108		Designing a high-density combined RF/B0 shim coil for imaging the brain at 7T
		Paul Chang¹, Sahar Nassirpour¹, Kaizad Rustomji², Elodie Georget², Ingmar Voogt³, Aidin Haghnejad³, Evita Wiegers⁴, Jannie Wijnen⁴, and Dennis Klomp⁴
		¹MR Shim GmbH, Reutlingen, Germany, ²Multiwave Imaging, Marseille, France, ³WaveTronica, Utrecht, Netherlands, ⁴UMC Utrecht, Utrecht, Netherlands
		Increased B0 inhomogeneity at ultra-high fields continues to pose a challenge for many MR applications. Local arrays of shim coils offer a complimentary way of reducing the local inhomogeneities. In this study, practical design considerations for a combined RF/B0 shim 7T head coil were assessed. Numerical simulations were used to find the optimal size and distance of the shim coils relative to Rx loops. These results were then verified in a bench test. Finally, having these considerations in mind, it was shown that by optimizing the arrangement of the shim coils improved B0 homogeneity can be achieved.

3109		Shielded coaxial cable coils for transmit, receive and B0 shimming in a 7T neck array
		Vincent O. Boer¹, Jan Ole Pedersen², Hørður Andreasen³, Sadri Güler^1,4, Vitaliy Zhurbenko³, Jason Stockmann⁵, Irena Zivkovic⁶, and Esben Thade Petersen^1,4
		¹Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital, Hvidovre, Denmark, ²Philips Healthcare, Copenhagen, Denmark, ³Department of Electrical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark, ⁴Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kongens Lyngby, Denmark, ⁵Athinoula A Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ⁶Electrical Engineering department, Technical University of Eindhoven, Eindhoven, Netherlands
		Shielded coaxial RF coils show very low coupling between elements, and are ideal for building transmit-receive arrays. In this work we extended a 6 element transceive array with B₀ shim capabilities.

3110		Improving MRI Near Metal with Local B0 Shimming using a Unified Shim-RF Coil (UNIC): First Case Study, Hip Prosthesis in Phantom.
		Fardad Michael Serry¹, Junzhou Chen^1,2, Anthony G Christodoulou^1,2, Yuheng Huang^1,2, Fei Han³, Won Bae^4,5, Christine Chung^4,5, Richard Handlin¹, John Stager¹, Matthew Dausch¹, Yubin Cai¹, Yujie Shan¹, Yucen Liu¹, Yibin Xie¹, Xiaoming Bi³, Rohan Dharmakumar^1,2, Zhaoyang Fan^1,6, Debiao Li^1,2, Hsin-Jung Yang¹, and Hui Han¹
		¹Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, United States, ²Department of Bioengineering, UCLA, Los Angeles, CA, United States, ³Siemens Medical Solutions USA, Inc., Los Angeles, CA, United States, ⁴University of California, San Diego, San Diego, CA, United States, ⁵VA Medical Center, San Diego, CA, United States, ⁶University of Southern California Department of Radiology, Los Angeles, CA, United States
		Metal artifact image degradation can interfere with tissue status assessment. Metal artifact reduction pulse sequences, mainly spin-echo based, and scanner B0-shimming can mitigate the artifacts. We have tested in a metal hip prosthesis phantom improving shimming locally with a novel technology that integrates separate but co-planar RF receive and shim arrays, expanding the freedom to position shim coils and shape B0, independently of the RF coil geometry and pulse sequence. Metal-induced signal-void artifact was reduced in GRE scans, revealing up to 50% additional area around the prosthesis. The sequence-agnostic technology may help improve MRI near metal prostheses and interventional devices.

3111		Shimming-Toolbox: An open-source software package for performing realtime B0 shimming experiments
		Alexandre D'Astous¹, Ryan Topfer¹, Gaspard Cereza¹, Eva Alonso-Ortiz¹, Lincoln Craven-Brightman², Jason Stockmann^2,3, and Julien Cohen-Adad^1,4
		¹NeuroPoly Lab, Institute of Biomedical Engineering, Ecole Polytechnique, Montreal, QC, Canada, ²Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ³Harvard Medical School, Boston, MA, United States, ⁴Functional Neuroimaging Unit, Centre de recherche de l'Institut universitaire de gériatrie de Montréal, Montreal, QC, Canada
		As MRI static fields get increasingly stronger, reducing $$$B_0$$$ inhomogeneities becomes more important but also challenging. When standard active shimming on commercial systems is insufficient for researchers’ needs, alternative approaches such as external shim or hybrid AC/DC coils can be used. However, in order to perform advanced shimming experiments, a proper software ecosystem is required and there is currently no open-source solution for transparent and reproducible shimming experiments. Here we introduce the Shimming Toolbox (https://shimming-toolbox.org), an open-source software package for performing and prototyping static, dynamic and realtime $$$B_0$$$ shimming experiments.

3112		Magnetic fields produced by simple coils inside finite-length cylindrical passive shields with end-caps
		Richard W. Bowtell¹, Michael Packer ², Peter Hobson ², James Leggett¹, Niall Holmes¹, Paul Glover ¹, Matthew Brookes¹, and Mark Fromhold²
		¹Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, United Kingdom, ²School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom
		Cylindrical shields formed from material of high permeability are commonly used in providing low-magnetic field environments for experimental research. Cylindrical coils are often sited inside such shields to produce controlled patterns of field variation, but interaction of the coils with the mu-metal distorts the fields. Here we show how to analytically calculate the fields that are produced by simple coils inside a finite-length, cylindrical mu-metal shield with end-caps, and report experimental measurements on two different coils (loop and saddle), demonstrating excellent agreement with the theory. Optimal spacings of Helmholtz-type coils inside finite-length shields are also derived using the analytic expressions.

3113		Hardware developed for phase and frequency locking of interleaved MRI and DMI studies
		Terence W. Nixon¹, Yanning Liu¹, Henk M. DeFeyter¹, Scott McIntyre¹, and Robin A. de Graaf¹
		¹Yale University, New Haven, CT, United States
		Deuterium metabolic imaging (DMI) is a powerful new method to supplement the anatomical and functional information of MRI with a metabolic component. A reduction in overall scan time by interleaving MRI and DMI is clinically relevant, whereas research applications can benefit from complimentary information obtained through interleaved acquisition. Because most MR scanners only allow acquisition of one frequency, additional hardware is required to enable interleaved acquisition. Here we present hardware for the upconversion of 2H data into the 1H receive path and present a solution to achieve effective phase and frequency locking.

3114		Simultaneous transmit/receive for Bloch-Siegert encoding: a feasibility study
		Baosong Wu¹, Sajad Hosseinnezhadian², Yonghyun Ha², Kartiga Selvaganesan², Charles Rogers III², Kasey Hancock², Gigi Galiana², and R. Todd Constable²
		¹Department of Radiology and Biomedical Imaging, Yale School of Medicine, NEW HAVEN, CT, United States, ²Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States
		This work presents the feasibility of Bloch-Siegert (BS) frequency encoding for magnetic resonance (MR) applications requiring a simultaneous transmit and receive system. RF frequency encoding technique is referred to receiving MR signal while existing one offset-field radiation, which can be considered as a radio frequency interference(RFI). A prototype was built demonstrating first MR experiment and preliminary data using this method. Our system is currently a research technology with the goal of generating a low-field and point-of-care medical imaging system using novel RF encoding.

3115		RF sinc pulse distortion compensation using multiple square pulses at 1 MHz.
		Yonghyun Ha¹, Kartiga Selvaganesan¹, Baosong Wu¹, Kasey Hancock¹, Charles Rogers III¹, Sajad Hosseinnezhadian¹, Gigi Galiana¹, and R. Todd Constable¹
		¹Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States
		The response times of RF coils in MRI are long when operating at low B₀ field, making it difficult to achieve the desired pulse shape in the coil. Compensation pulses are shown that were optimized using a series of square pulses. Both the duration and amplitude of the compensation elements were calculated with Q-factor which was calculated from the ring-down time measured using a sniffer coil. The SNRs of the echo signal acquired using compensated pulse was compared with those of signal obtained with uncompensated pulses and showed significant improvements of 51.5%.

3116		Automatic 3D B1 field mapping using 3D printer and digital oscilloscope for gradient-free MRI system
		Yonghyun Ha¹, Kartiga Selvaganesan¹, Sajad Hosseinnezhadian¹, Baosong Wu¹, Kasey Hancock¹, Gigi Galiana¹, and R. Todd Constable¹
		¹Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States
		For gradient-free RF spatial encoding, MR image based B₁ mapping methods cannot be used due to the absence of gradient coils. However, it is important to get a B₁ map particularly if Bloch-Siegert shift encoding is used. In this work, a method to automatically measure the amplitude of B₁ field is introduced. Three perpendicular pickup loops were used to measure the B₁ field in three orthogonal axes simultaneously. The position of the pickup loops was controlled by 3D printer, and the peak-to-peak voltage of the coupled signal was automatically saved using PC oscilloscope.

3117		Inhomogeneity and ramping effects in field-cycled quantitative molecular MRI
		Matthew A. McCready¹, William B. Handler¹, Francisco Martinez^2,3, Timothy J. Scholl^2,3, and Blaine A. Chronik^1,2
		¹Physics and Astronomy, Western University, London, ON, Canada, ²Medical Biophysics, Western University, London, ON, Canada, ³Robarts Research Institute, Western University, London, ON, Canada
		Delta relaxation enhanced magnetic resonance (dreMR) is a field-shifting quantitative molecular imaging method. The dreMR method may be used to produce images with signal proportional to concentration of contrast agents with longitudinal relaxivity dispersion. Here we find that field inhomogeneities and ramping periods, which were previously ignored, cause significant errors in dreMR images. These errors include apparent non-zero signal from dispersion-free tissue, and apparent change in signal due to contrast agents. We show that these effects can be mitigated by use of an improved homogeneity design method, and increased slew rates.

3118		Very low field MRI for brain imaging
		Samson Lecurieux Lafayette¹ and Claude Fermon¹
		¹SPEC - CEA Saclay - Université Paris Saclay, Saclay, France
		Classic high field MRI is a powerful tool in healthcare. However, it is an expensive and complex installation and it might be useful to supply a less convenient device adapted to a lot of usage not requiring high field potential. We have developed a very low field MRI working at between 1mT and 10mT. Main static field is providing by a water-cooled resistive magnet. In order to achieve an iso spatial resolution of 2mm in a reasonably short time of acquisition, we have worked on adapted sequences including compressed sensing and optimized detection with parallel acquisition.

3119		Comparison of SNR between a low-field (0.26T) Tabletop-MRI and a clinical high-field (3T) scanner
		Robert Kowal¹, Enrico Pannicke², Marcus Prier¹, Ralf Vick², Georg Rose³, and Oliver Speck¹
		¹Department of Biomedical Magnetic Resonance, Otto von Guericke University, Magdeburg, Germany, ²Chair of Electromagnetic Compatibility, Otto von Guericke University, Magdeburg, Germany, ³Chair in Healthcare Telematics and Medical Engineering, Otto von Guericke University, Magdeburg, Germany
		The SNR-performance of a low-field (0.26T) Tabletop-MRI-system was experimentally compared to a high-field (3T) clinical scanner. The SNR of simple FID sequences were evaluated for RF-units with identical coil and sample geometries as well as T/R-switch designs. The SNR was calculated from time signals and put into perspective to compute the relative SNR-performance of the Tabletop-system which was measured at 11.3%. Additional compensations for several differing experimental conditions were carried out. The full comparison suggests limiting factors in the equivalent measurement in the clinical scanner which can result in more SNR loss than expected.

3120		Initial Experience of Body Imaging at 5T
		Zhenhua Shen¹, Xuchen Zhu¹, Shihong Han¹, Fuyi Fang¹, Wei Luo¹, Shao Che¹, Zidong Wei¹, Jinguang Zong¹, Yongquan Ye², Bo Li¹, Shuheng Zhang¹, Anthony Vu², Weiguo Zhang², and Guobin Li¹
		¹United Imaging Healthcare, Shanghai, China, ²UIH America, Inc., Houston, TX, United States
		For the first time, routine clinical body imaging with large FOV on a whole-body 5T MRI system is demonstrated. With multi-channel RF parallel transmission hardware architecture and static RF shimming techniques, the uniformity of the RF transmission field is shown to be well controlled for imaging quality guarantee. Preliminary results show great promise for body imaging at 5T.

3121		A sample temperature control system for post mortem MRI
		Sebastian Walter Rieger¹, Karla Miller¹, Peter Jezzard¹, and Wenchuan Wu¹
		¹Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, United Kingdom
		In post mortem MRI, the absence of body temperature autoregulation can lead to significant local heating in the sample from RF absorption and heat from the environment. This can interfere with scanning (such as diffusion measurements) and in unfixed samples, accelerate tissue decomposition. In this work, a temperature control system is presented which enables prolonged scanning of post mortem samples at a stable temperature while preserving tissue.

3122		Compact MRI bioreactor for real-time monitoring 3D printed tissue-engineered constructs.
		Jean-Lynce GNANAGO^1,2,3,4,5,6, Tony GERGES^1,2,3,4,5,6, Laura Chastagnier^{1,2,4,6,7,8,9,10}, Emma Petiot^{2,4,6,7,8,9,10}, Vincent SEMET^1,2,4,5,6, Philippe Lombard^1,2,3,4,5,6, Christophe Marquette^{1,2,4,6,7,8,9,10}, Michel Cabrera^1,2,3,4,5,6, and Simon Auguste Lambert^1,2,3,4,5,6
		¹Université Claude Bernard Lyon 1, VILLEURBANNE, France, ²INSA LYON, VILLEURBANNE, France, ³Ecole Centrale Lyon, Ecully, France, ⁴CNRS, VILLEURBANNE, France, ⁵AMPERE UMR 5005, VILLEURBANNE, France, ⁶Université de Lyon, VILLEURBANNE, France, ⁷3d.FAB, VILLEURBANNE, France, ⁸CPE Lyon, VILLEURBANNE, France, ⁹ICBMS, VILLEURBANNE, France, ¹⁰UMR 5246, VILLEURBANNE, France
		Tissue engineering for regenerative medecine is a growing field which faces structural and functional challenges at different scales. Real-time quantitative 3D characterization of tissues both in vitro and in vivo would help biologists assessing their methods. Magnetic Resonance Imaging (MRI) offers the possibility to perform such characterization non-invasively. We propose here a 7T MRI coil integrated within a perfusion tissue engineering bioreactor to perform tissue assessments throughout its growth. The MRI bioreactor is built using 3D printing and plastronics. This works resulted in a successful observation of a bioprinted tissue with a 75 µm in plane resolution.

3123		Characterization of 3AM diffusion MRI phantoms via microscopy, and phase-contrast micro-CT
		Farah Mushtaha^1,2, Tristan K. Kuehn^1,3, Omar El-Deeb⁴, Seyed A. Rohani³, Luke W. Helpard³, Hanif Ladak^2,3,5, Amanda Moehring⁶, Corey A. Baron^1,2,3,7, and Ali R. Khan^1,2,3,7
		¹Robarts Research Institute, London, ON, Canada, ²Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada, ³School of Biomedical Engineering, Western University, London, ON, Canada, ⁴Neuroscience, Western University, London, ON, Canada, ⁵Department of Electrical and Computer Engineering, Western University, London, ON, Canada, ⁶Biology, Western University, London, ON, Canada, ⁷The Brain and Mind Institute, Western University, London, ON, Canada
		Validating diffusion MRI (dMRI) representations and models of brain tissue is challenging because there is no reference ground-truth for in vivo scans. We investigate the microstructural characteristics of 3D printed axon-mimetic (3AM) phantoms as a dMRI validation tool using fluorescence microscopy and phase-contrast micro computed tomography (micro-CT). Both microscopy and micro-CT yielded pore diameters of ~ 8 μm. We constructed a 2-compartment microstructural model using microscopy and micro-CT data to simulate 3AM dMRI scans, and compared the observed metrics from in-vivo scans and simulation data.

3124		A phantom system for evaluating the effect of lipid and iron composition on qMRI parameters
		Rona Shaharabani¹, Shir Filo¹, Oshrat Shtangel¹, and Aviv Mezer¹
		¹The Edmond and Lily Safra Center for Brain Science, The Hebrew University of Jerusalem, Jerusalem, Israel, Jerusalem, Israel
		Neurodegenerative diseases such as Alzheimer, Parkinson, and Multiple sclerosis are often linked to abnormal changes in lipids and iron. Lipids are the main components of any membrane, including myelin, and iron is an essential brain’s trophic. The interaction of lipids and iron with water protons is considered to be a major contributor to the brain’s MRI signals. Here we examine the combined effects of the iron and lipid compositions on quantitative MRI parameters using a novel phantom system. We quantitatively characterize the R2* dependence on lipid and iron concentrations.

Nobody's Perfect: Hardware & Patient Corrections

Systems Engineering II

Engineering/Interventional/Safety

3325		Single Half-Cylinder B0 Shim Coil for the Knee
		Mingdong Fan¹, Sugandima Nishadi Weragoda¹, Benjamin Cheung¹, Michael Martens¹, Labros Petropoulos², Xiaoyu Yang², Shinya Handa², Noah Deetz², Hiroyuki Fujita², and Robert Brown¹
		¹Case Western Reserve University, Cleveland, OH, United States, ²Quality Electrodynamics, Mayfield, OH, United States
		The void under the knee of a supine patient leads to localized B0 magnetic field distortions due to air-tissue susceptibility differences. To cancel this local artifact, low-order harmonic shims are inadequate, but a single local shim coil can produce higher harmonic suppression. A half-cylinder version wrapped on the outside of the RF coil has been constructed and used to obtain in vivo data consistent with the magnetic field simulations. The detailed results support the possibility of an effective knee shimming approach.

3326		B0 Susceptibility-Induced Geometric Image Distortion at Low-Field for Magnetic Resonance Imaging in Radiation Therapy
		Manuel Schneider¹, Sylvain Doussin¹, Dieter Ritter¹, and Martin Requardt¹
		¹Siemens Healthcare GmbH, Erlangen, Germany
		Our main purpose was to quantify geometric image distortion due to reduced susceptibility at 0.55T compared to 1.5T. Therefore, Bloch simulations of a digital phantom and a 2D GRE sequence were performed. The simulations at both field strengths were calculated twice: once without considering B0 susceptibility, and once considering B0 susceptibility artefacts. Additionally, 3D T2 SPACE images with high readout bandwidth as well as echo-planar diffusion-weighted images were obtained and compared in n=3 volunteers. Less geometric distortion due to B0 susceptibility artefacts was observed at 0.55T compared to higher field strengths.

3327		Hybrid Active and Passive Local Shimming (HAPLS) for Two-region Magnetic Resonance Imaging (MRI)
		Zhi Hua Ren¹, Jason P. Stockmann^2,3, Andrew Dewdney⁴, and Ray F. Lee¹
		¹Zuckerman Institute, Columbia University, New York, NY, United States, ²Harvard Medical School, Boston, MA, United States, ³Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States, ⁴Siemens Healthcare GmbH, Erlangen, Germany
		When the bilateral regions of intersest are far off isocenter like in case of shoulders or for brains of two people to be scanned simultaneously, the image quality often suffers from non-optimal spherical harmonic based shimming routine and higher field inhomogeneity in large off-isocenter regions. To address these challenges, a hybrid active and passive local shimming (HAPLS) technique is proposed to shim two isolated areas in one field of view (FOV) simultaneously. Both the simulation and experimental results validated that HAPLS can complementarily address the bifocal and high-order inhomogeneities in the two-region MRI.

3328		Characterization of 3rd order shim system of human 7T MRI system demonstrates the need of real shim field calibration
		Mahrshi Jani¹, Ivan Dimitrov¹, Bei Zhang¹, Binu Thomas¹, and Anke henning¹
		¹Advance Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States
		To perform magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS)in high and ultra-high field homogeneity of field (B0) is required to improve image quality and obtainable metabolic information form MRI scan. In this work we present, real shim field calibration to improve homogeneity of B0 field. The vendor implemented B0 shim system consists of one 0th order, three 1st order, five 2nd order and seven 3rd order shim coils. The proposed calibration to be implemented in existing stand-alone Philips system and further application software shall be developed to integrate latest algorithms and methods to B0 shimming.

3329		The Spherical Harmonic Rating: A Metric for B0 Shim System Performance Assessment
		Bruno Pinho-Meneses¹ and Alexis Amadon¹
		¹Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
		Different B₀ shim system designs are tested on two distinct fieldmap databases for assessment of commonly employed metrics for evaluation of B₀ inhomogeneity mitigation. We verify that those metrics might not always be the best choice for performance analysis, as, for a same shim system, they may provide hardly comparable values across sites. We then propose a novel, simple and robust metric for shim system analysis, the Spherical Harmonic Rating, which is shown to provide consistent performance across sites, providing an equivalency of the shim system to a Spherical Harmonics basis.

3330		On-coil B0 shimming with a flexible coaxial coil element at 3 T
		Bernhard Gruber^1,2, Maxim Zaitsev¹, and Elmar Laistler¹
		¹High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²Department of Radiology, A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
		The combination of highly flexible RF coils and on-coil shimming is an interesting concept, in particular for applications in body parts that have strong inter-patient variability, such as breast, thorax or abdomen. The well-known AC/DC approach on rigid standard loop coils involves many bulky RF chokes and would therefore not be suitable for flexible coil elements. In the presented approach coaxial coils are used instead, where no segmenting capacitors and correspondingly no RF chokes are required. We demonstrate that this conceptual design shows good RF performance and the created magnetic fields for shimming are in good agreement with analytical calculations.

3331		Open-Source Gradient Impulse Response Function (GIRF) calibration measurements and their impact in Spiral acquisition
		Tiago Timoteo Fernandes¹, Andreia S Gaspar¹, Andreia C. Freitas¹, Nuno A. da Silva², and Rita G Nunes¹
		¹Institute for Systems and Robotics - Lisboa and Department of Bioengineering, IST-UL, Lisbon, Portugal, ²Hospital da Luz Learning Health, Lisbon, Portugal
		A major challenge in MRI, particularly when aiming to reduce equipment costs, is to be able to cope with imperfect hardware performance. Even when using current clinical systems, calibration is often required to reduce image artifacts; an example is the impact of eddy-currents in spiral readouts. Here we controlled for this effect by determining the gradient impulse response function (GIRF) using an open source calibration pulse sequence, demonstrating the impact of the GIRF and its correction both through simulation and in real phantom data. This implementation will contribute towards the development of open source tools for spiral imaging.

3332		Correct K-space coordinates and gradient coupled $$$B_0$$$ variation for Spiral imaging using the current monitor
		Tzu-Cheng Chao¹, Jürgen Rahmer², Sandeep Ganji³, Guruprasad Krishnamoorthy³, Peter Börnert², and James G. Pipe¹
		¹Department of Radiology, Mayo Clinic, Rochester, MN, United States, ²Philips Research, Hamburg, Germany, ³Philips Healthcare, Gainesville, FL, United States
		Error from inaccurate eddy current assessment has been a critical issue in spiral imaging. A model is established to estimate both the gradient field and its induced B0 variation from the measured current of the gradient amplifier. The correction improves the geometric consistency between both spiral-in and spiral-out images. The results suggest that the present work have potential to improve quality of spiral imaging.

3333		On the predictability of B0 maps at ultra-high fields using deep learning
		Vidya Prasad¹, Sharun S Thazhackal¹, Ashvin Srinivasan¹, Suja Saraswathy¹, Jaladhar Neelavalli², and Umesh Rudrapatna²
		¹Philips Research, Philips, Bangalore, India, ²Philips Healthcare, Philips, Bangalore, India
		UHF-MRI offers increased scanning sensitivity, but suffers from pronounced B₀ inhomogeneities. B₀ maps are essential for shimming and reconstruction at UHFs, but suffer from scanning overhead and low measurement confidence. Predicting B₀ maps from survey scans can effectively address these issues. We assessed predictability of brain B₀ maps at 7T and 11.7T using deep learning on a large synthetic B₀map dataset created from 540 CT images. We found that deep learning can predict 1) spherical harmonics for shimming and 2) the complete B₀ maps. Our results indicate that B₀ predictions work as effectively as acquiring B₀ maps for shimming.

3334		A new route of ultrahigh field MRI shimming: hybrid superconducting matrix coil and multi-order spherical harmonics room-temperature shim coils
		Yaohui Wang^1,2, Qiuliang Wang^1,2, Yang Liu¹, Jigang Zhao¹, Hui Wang¹, Junsheng Cheng¹, and Feng Liu³
		¹Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China, ²University of Chinese Academy of Sciences, Beijing, China, ³School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia
		A new route for ultrahigh field MRI shimming was proposed which utilized hybrid superconducting matrix coil and multi-order room-temperature shim coils. The proposed scheme was aimed to create a stable and accurate shimming solution for high homogeneous magnetic field magnet. A real 9.4T whole-body MRI magnetic field profile was used to validate the shimming strategy and a remarkable effect was achieved. Therefore, the new shimming method deserves to generalize to ultrahigh field MRI system.

3335		Eight channel B0 shim array as add-on for ultra-high field systems
		Jan Ole Pedersen¹, Esben Thade Petersen^2,3, Jason Stockmann⁴, and Vincent O. Boer²
		¹Philips Healthcare, Copenhagen, Denmark, ²Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital, Hvidovre, Denmark, ³Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kgs Lyngby, Denmark, ⁴Athinoula A Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States
		We have simulated and manufactured a shim coil array specifically designed to address fronto-temporal B₀ inhomogeneities at 7T. The shim array is driven by an open-source amplifier, and facilitates slice-wise dynamic shimming. Complexity and costs are purposely kept low to allow manufacturing without prior expertise in electronics design and without access to extensive electronics manufacturing facilities.

3336		Studies of the static field homogeneity artefacts induced by the diamagnetism of HTS coils and solution to avoid them
		Aimé Labbé¹, Rose-Marie Dubuisson¹, Jean-Christophe Ginefri¹, Cornelis J van des Beek², Luc Darrasse¹, and Marie Poirier-Quinot¹
		¹Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France, ²Université Paris-Saclay, CNRS Center for Nanoscience and Nanotechnology, Palaiseau, France
		High-Temperature Superconducting (HTS) radiofrequency coils can improve sensitivity by more than an order of magnitude, but their propensity to warp the magnetic field as a result superconducting diamagnetism could cause image degradation. We report on the observation of these B₀ artefacts. They are shown to be predominant at lower working temperatures of the HTS coil (60 K) and negligible at 80 K and can be avoided altogether by cooling the HTS coil in B₀. We also propose a phenomenological model of these field perturbations. This work studies and solves an important issue in the integration of HTS coil in MRI.

3337		Bloch-Siegert \|B1+\|-Selective Excitation Pulses
		Jonathan B Martin¹, Christopher E Vaughn¹, Mark A Griswold², and William A Grissom¹
		¹Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Radiology, Case Western Reserve University, Cleveland, OH, United States
		We present a new class of pulses which utilize the Bloch-Siegert shift to localize a \|B₁⁺\| selective excitation. The summation of a far-off-resonant pulse inducing a \|B₁⁺\|-dependent Bloch-Siegert shift and a frequency-selective excitation pulse excites spins depending on the strength of transmit field that they experience. The passband of the pulse can be shifted by adjusting the frequency modulation of each of the component pulses. We verify the ability of the new pulse to produce a selective excitation in simulation and on a scanner.

3338		B1+ Homogenization in 3D Liver MRI at 7 Tesla Using Eight-Channel Parallel Transmission: Kt-points vs. Phase Shimming
		Bobby Runderkamp¹, Thomas Roos², Wietske van der Zwaag², Matthan Caan³, Gustav Strijkers³, and Aart Nederveen¹
		¹Radiology and Nuclear Medicine, Amsterdam UMC, Amsterdam, Netherlands, ²Spinoza Center for Neuroimaging, Amsterdam, Netherlands, ³Department of Biomedical Engineering and Physics, Amsterdam UMC, Amsterdam, Netherlands
		Abdominal MRI at ultra-high field benefits from increased SNR but is challenged by high B1+-inhomogeneity. We use eight-channel parallel transmission to homogenize B1+ signal in 7T liver MRI and compare CP-transmission against phase shimming and a kt-points pulse. Increased signal homogeneity was obtained with the kt-points pulse and phase shimming compared to CP-transmission for small volunteers. Combining the kt-points pulse with a compressed sensing reconstruction facilitated single breath-hold high-resolution liver MRI. With improved B1-mapping and kt-point optimization, kt-points is expected to also improve homogeneity in larger volunteers, and to outperform phase shimming in achieving homogeneous signal in 7T liver MRI.

3339		Magnitude Least Squares RF Shimming with Singular Vector Minibatching
		Jonathan B Martin¹, Benjamin M Hardy², and William A Grissom¹
		¹Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Physics and Astronomy, Vanderbilt University, Nashville, TN, United States
		Magnitude-least squares optimization is widely used to design RF shims that produce homogeneous B₁⁺ fields at high field strengths, but the MLS optimization problem is non-convex and prone to becoming stuck in local minima corresponding to unacceptable voids in the shimmed field. We describe a simple, improved Gerchberg-Saxton algorithm for MLS RF shimming in which randomly selected subsets of the B₁⁺ map matrix's singular vectors are used in each shim update. Shims are then refined using conventional GS. Simulations of 8- and 30-channel head coils at 7T verify the method's robustness, and demonstrate advantages over conventional RF shim design techniques.

3340		A universal framework to build digital reference objects for evaluation of quantitative MRI analysis with multiple measurements
		Henry Szu-Meng Chen¹, Brian A Taylor¹, Joshua P Yung¹, Ping Hou¹, R. Jason Stafford¹, and Ho-Ling A Liu¹
		¹Imaging Physics, MD Anderson Cancer Center, Houston, TX, United States
		We propose a framework to easily design and generate digital reference object (DRO) s that conforms with DICOM standard for testing quantitative MRI analysis. The method focuses on using existing phantom scan as the basis and allows user to customize the phantom’s geometry and signal model. We generated a number of DRO for T2* and DSC quantitation and analyzed them with two different software as proof-of-concept.

3341		Robust real-time 3D motion estimation with MR-MOTUS on an MR-LINAC: a multi-subject validation study
		Niek RF Huttinga¹, Tom Bruijnen¹, Cornelis AT van den Berg¹, and Alessandro Sbrizzi¹
		¹Department of Radiotherapy, Computational Imaging Group for MR therapy & Diagnostics, University Medical Center Utrecht, Utrecht, Netherlands
		In this work we tighten the gap towards clinical application of MR-MOTUS for real-time tracking of non-rigid 3D respiratory motion-fields during MR-guided radiotherapy. The framework is extended from an experimental setting on a conventional 1.5T MR-scanner, to a practical setting on an MR-LINAC: multi-coil and free-breathing data acquisitions, and the possibility for validation at high temporal resolution. 3D motion-field reconstructions are performed in 160ms/dynamic, for a total of five volunteers. Validations show that spatially realistic motion-fields are reconstructed that have 0.94$$$\pm$$$0.018 temporal correlation with a conventional respiratory-motion surrogate, while satisfying the clinical latency requirement of 5Hz for MR-guided radiotherapy.

3342		Investigation of respiration-induced changes of the scattering matrix by EM simulations and a breathing body model
		Natalie Schön¹, Frank Seifert¹, Gregory J. Metzger², Bernd Ittermann¹, and Sebastian Schmitter^1,2
		¹Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany, Berlin, Germany, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
		Respiratory motion is a fundamental challenge for thorax MR imaging, particular at ultra-high fields. Recent in-vivo studies have shown that the coil's time-dependent scattering matrix (S-Matrix) can be used for respiration gating to minimize those artefacts. Here, we present electromagnetic simulations of the respiration-induced changes of the transmit RF coil’s S-matrix. Analysing the impact of breathing patterns (conventional, chest, abdominal) illustrates the combined effects of chest/diaphragm motion. The type of respiratory motion and RF coil geometry, position and element type are shown to impact the S-Matrix with implications on coil performance, respiratory triggering, power monitoring and RF pulse design.

3343		Using gradient-readout, fast spectroscopic imaging and a 3D multi-echo GRE acquisition for scanner Quality Assurance (QA)
		Claudiu Schirda¹
		¹Radiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
		We propose using a gradient readout, fast MRSI acquisition and a support or stand-alone 3D multi-echo, 3-point Dixon GRE scan for MRI scanner and coil quality assurance (QA). The fast MRSI acquisition with the support 3D GRE scan uses the BRAINO phantom, takes less than 10 minutes and could be used for 1 to 3 months QA. A modified (with an increased FOV), stand-alone 3D GRE scan, takes 3-minutes, could be used either with a spherical or cylindrical phantom and is proposed for daily QA, in addition to the manufacturer EPI-based stability scan. Fully automated reconstruction programs provided at github.com/FastMRSI.

3344		A New Representation of the Gradient System Transfer Function Using a Practical Algorithm of Finite Impulse Response Filters
		Hidenori Takeshima¹
		¹Advanced Technology Research Department, Research and Development Center, Canon Medical Systems Corporation, Kanagawa, Japan
		This work proposes a new representation of the gradient system transfer function (GSTF) based on finite impulse response (FIR) filters. FIR filters can represent arbitrary gradient functions but are not used because of their computational complexity. The proposed method represents the GSTF as a set of average coefficients and their durations. Input signals are represented as sums of signals for the same durations. On an update step, only two signals are accessed for each duration. Therefore, as confirmed experimentally, the proposed method can process arbitrary gradient functions in acceptable computational time, without using infinite impulse response (IIR) filters.

Toolbox: Software & Phantoms

Systems Engineering II

Engineering/Interventional/Safety

3345		Cube set for the quantification of 3-dimensional spatial resolution in MR- micro imaging and microscopy (a = 128 - 4 µm) using 2-photon lithography
		Andreas Georg Berg^1,2, Stefan Hengsbach³, and Klaus Bade³
		¹Center for Medical Physics and Biomedical Engineering High field MR-Center, Medical University of Vienna, Vienna, Austria, ²High-Field MR-Center (MRCE), Medical Universits of Vienna, Vienna, Austria, ³Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), Leopoldshafen-Eggenstein, Germany
		Quality-control for systematic improvements in 3D-isotropic spatial resolution of the MR-imaging system up to the microscopic range becomes increasingly relevant not only for preclinical imaging but also for High-Field-MR human scanners. The design of a prototype phantom, comprising a set of 3D-cubes and an exemplary MR-microscopic evaluation is presented. The extraordinary challenges on accurate bar-width-to-cavity ratios for the cube range from periodicity a=128µm down to a=4µm are dealt with using 2-photon-lithography as manufacturing technology. The spatial resolution for 3D isotropic imaging can be checked qualitatively and quantitatively by interpolation of the Modulation-Transfer-Function demonstrated on a 3D-GRE sequence as an example.

3346		En Route to multiphasic anthropomorphic MR phantoms: An additive manufacturing approach applying silicone 3D-printing techniques
		Wolfgang Kilian¹, Rüdiger Brühl¹, Yasser Abdulhadi¹, and Bernd Ittermann¹
		¹Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany
		Stable and well characterized anthropomorphic MR-phantoms for quantitative MRI of T1 and T2 measurements are still lacking. We investigate the potential application of additive manufacturing of silicone to produce multi-compartment MR-phantoms with well characterized relaxation properties. Various two-component silicone types with different mixture ratios were investigated. Additionally, the influence of admixing colors to modulate relaxation times was studied. First bi-phasic test samples were designed, produced by different commercial 3D printing sources, and characterized.

3347		En route to multiphasic anthropomorphic MR phantoms: A new mold-based approach applying gel-based preparation to real MR-datasets geometries
		Adriano Troia¹, Umberto Zanovello¹, Luca Zilberti¹, Matteo Cencini², Michela Tosetti^2,3, David Kilian⁴, Martina Capozza⁵, Wolfgang Kilian⁶, and Tuğba Dışpınar Gezer⁷
		¹INRIM, Turin, Italy, ²IRCCS Stella Maris, Pisa, Italy, ³IMAGO7 Foundation, Pisa, Italy, ⁴Centre for Translational Bone, Joint and Soft Tissue Research, Faculty of Medicine and University Hospital TUD, Dresden, Germany, ⁵Department of Molecular Biotechnology and Health Sciences UNITO, Turin, Italy, ⁶Physikalisch-Technische Bundesanstalt, Braunschweig, Germany, ⁷National Metrology Institute, TUBITAK, Istanbul, Turkey
		Anthropomorphic phantoms for MRI imaging are rapidly evolving also thanks to the increase of 3D printing technologies. Their realization may represent an important support for the implementation of advanced quantitative imaging technique such as Magnetic Resonance Fingerprinting (MRF)or Electrical Properties Tomography (EPT). Even if formulations of gel based tissue-mimicking materials have been widely explored, generally they lacked in achieving the simultaneous tuning of electrical and relaxation properties of the mimicked tissues. In this study, customized moulds of white and grey matter are combined to realize brain-like gel phantoms in which relaxation times, conductivity and permittivity have been measured.

3348		A Method for Alignment of an Augmented Reality Display of Brain MRI With The Patient’s Head
		Christoph Leuze¹, Supriya Sathyanarayana¹, Bruce L Daniel¹, and Jennifer A McNab¹
		¹Radiology, Stanford University, Stanford, CA, United States
		We present a method for alignment of augmented reality display of brain MRI with the patient’s real-world head with potential applications to an AR-neuronavigation system that relies on a see-through display.

3349		Specialized Computational Methods for Denoising, B1 Correction, and Kinetic Modeling in Hyperpolarized 13C MR EPSI Studies of Liver Tumors
		Philip Meng-en Lee¹, Hsin-Yu Chen¹, Jeremy W Gordon¹, Zihan Zhu¹, Peder EZ Larson¹, Nicholas Dwork¹, Mark Van Criekinge¹, Lucas Carvajal¹, Michael A Ohliger¹, Zhen J Wang¹, Duan Xu¹, John Kurhanewicz¹, Robert A Bok¹, Rahul Aggarwal², Pamela N Munster², and Daniel B Vigneron¹
		¹Department of Radiology & Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Department of Medicine, University of California, San Francisco, San Francisco, CA, United States
		The inhomogeneous B₁ excitation profile of ¹³C surface transmit/receive coils provides high SNR near the surface, but results in a spatially-varying B₁+. For accurately quantifying the pyruvate to lactate conversion rate (k_PL), the flip angle needs to be corrected based on the B₁ excitation profile. Simultaneously, random noise in hyperpolarized spectral data obscures peaks of downstream metabolites. In this work, we developed and tested a specialized computational pipeline incorporating denoising and a B₁ excitation field correction method that improved quantitative kinetic rate analyses of hyperpolarized ¹³C MRSI scans of liver tumor patients acquired with a T/R ¹³C surface coil.

3350		A magnetic susceptibility phantom with large range of negative/positive values for quantitative validations
		Alexey Dimov¹, Kelly Gillen¹, and Yi Wang¹
		¹Radiology, Weill Cornell Medicine, New York, NY, United States
		A magnetic susceptibility phantom with a large range of negative to positive susceptibility values relative to water is demonstrated for validating quantitative susceptibility mapping (QSM) and related quantitative MRI techniques. The phantom consists of vials with various concentrations of paramagnetic Gadolinium contrast agent (Gd) and diamagnetic calcium chloride (CaCl2) solutions. Compared to previously reported phantoms, this phantom is easy to construct and highly stable and has minimal effects of unwanted air bubbles.

3351		3D Printed MRI Knee Phantom for Imaging Safety and Protocol Studies at Ultrahigh Fields
		Leo Konst Marecki¹, Eric Konst Marecki¹, and Xiaoliang Zhang¹
		¹Biomedical Engineering, SUNY University at Buffalo, Buffalo, NY, United States
		Most utilized phantoms for determining the SAR compose of a uniform material to determine the properties of each coil and the exposure time to remain below the FDA guidelines and ensure patient safety. Accurate modeling of the tissue permittivity, conductivity, and geometry will provide more accurate methods to measure the SAR of each organ for a variety of RF coil systems. Our results showed that utilizing 3D printed Nylon containers and Polyvinylpyrrolidone (PVP), NaCl, and water solutions can be used to model the geometry and tissue characteristics of the human knee.

3352		Development of an anthropomorphic torso and left ventricle phantom for flow and respiratory motion simulation
		Tito Körner¹, Stefan Wampl¹, Marcos Wolf¹, Martin Meyerspeer¹, Maxim Zaitsev^1,2, Wolfgang Birkfellner¹, and Albrecht Schmid¹
		¹High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²Medical Physics, Department of Radiology, University Medical Center Freiburg, Freiburg, Germany
		Development of motion compensation strategies is challenging, especially when involving volunteer measurements due to high demands to subject compliance and low reproducability. In this work a human shaped torso phantom, capeable of simulating respiratory motion of a left ventricle phantom including blood flow simulation is presented. A tracking algorithm is applied in postprocessing to acquired images containing simulated respiratory motion. Comparison to motion tracking data from an external sensor show good agreement proving the setup to be an environment with high reproducability and hence ideal for the purpose to develop and evaluate motion compensation strategies.

3353		3D printed head-shaped phantom with lipid layer and brain-mimicking metabolites for 7 Tesla MRI and MRSI
		Rita Schmidt^1,2, Ghil Jona³, and Edna Furman-Haran^2,3
		¹Neurobiology, Weizmann Institute of Science, Rehovot, Israel, ²The Azrieli National Institute for Human Brain Imaging and Research, Weizmann Institute of Science, Rehovot, Israel, ³Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
		Moving to ultra-high fields (≥7T), the inhomogeneity of both RF and static magnetic fields increases, which motivates to design a realistic head-shaped phantom. In this study, a 3D-printed head-shaped phantom with brain mimicking metabolites and lipid layer examined for 7T MRI and MRSI. The phantom was designed to resemble the brain with respect to B₀ and B₁ distributions, metabolites and lipid layer. We examined it for ¹H MRS and MRSI, especially in the lipid layer vicinity. We also demonstrated in EPI that the Fat Suppression pulse flip angle can be optimized to minimize the lipid artifact and reduce the SAR.

3354		Oil-in-water emulsions for tissue simulation in magnetic resonance imaging: Determination of MR-properties of emulsifiers
		Victor Fritz¹, Petros Martirosian¹, Jürgen Machann^1,2, Rolf Daniels³, and Fritz Schick¹
		¹Section on Experimental Radiology, University of Tübingen, Tübingen, Germany, ²Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich at the University of Tübingen, Tübingen, Germany, ³Institute of Pharmaceutical Technology, University of Tübingen, Tübingen, Germany
		The aim of this work was to develop stable and homogeneous oil-in-water emulsions for tissue simulation in MRI. For this purpose, three different emulsifiers (polysorbate 60, sodium dodecyl sulfate (SDS), and soy lecithin) were examined for their stabilizing ability. In addition, their potential impact on the MR-measurements was investigated. Sufficient stability can be achieved using both emulsifier, polysorbate and lecithin. Emulsions stabilized by SDS showed a visually lower stability. Due to its sufficient stabilizing ability, promising relaxometric properties (r_1,lecithin=0,11wt%^-1s^-1, r_2,lecithin =0,62wt%^-1s^-1), and no additional spectral resonances, lecithin is suggested as the preferred emulsifier for use in MRI.

3355		1:1 Scale Agar-Agar Paramagnetic Phantom for Brain and Cervical Spine MRI
		Elif Aygun^1,2, Ahmet Rahmetullah Cagil^1,2, and Emine Ulku Saritas^1,2,3
		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
		Phantoms doped with paramagnetic materials are commonly used for quality assessment of MRI protocols and image reconstruction techniques. These phantoms are typically prepared using cylindrical containers and mimic the T₁ /T₂ characteristics of human tissue. In this work, we propose a 1:1 scale human head and neck agar-agar phantom prepared using a 3D human model. The phantom mimics human tissue characteristics while incorporating the skull and cervical vertebrae. The MRI images show that the phantom closely matches human anatomy, and the susceptibility artifacts in EPI images successfully mimic those seen during in vivo imaging of the brain and spine.

3356		MRI System Phantom: assessing the MR visible thermometer, scanner geometric distortion corrections, and effect of fill conductivity
		Stephen E Russek¹, Kathryn E Keenan¹, Karl F Stupic¹, Teryn S Wilkes², Ramesh Karki³, and Todor Karaulanov⁴
		¹NIST, Boulder, CO, United States, ²Intermountain Neuroimaging Consortium, University of Colorado, Boulder, CO, United States, ³University of Colorado Anschutz, Radiological Sciences, Aurora, CO, United States, ⁴CaliberMRI, Inc., Boulder, CO, United States
		Using the MRI system phantom we demonstrate the utility of the embedded MR-readable thermometer to measure and correct for temperature variations, demonstrate the use of the fiducial array to characterize scanner geometric distortions and the efficacy of software distortion corrections, and finally look at the effect of the electromagnetic properties of the phantom fill on quantitative measurements.

3357		A novel MRI phantom to study the fluid dynamics of the glymphatic system: a proof-of-concept study
		Endre Grøvik^1,2, Elisabeth Lysvik¹, Robin Bugge¹, Kyrre Emblem¹, Trine Hjørnevik¹, Svein-Are Vatnehol¹, and Tryggve Storås¹
		¹Oslo University Hospital, Oslo, Norway, ²University of South-Eastern Norway, Drammen, Norway
		The proposed glymphatic system is hypothesized to be a waste-clearance system of the cerebrospinal fluid (CSF) through the perivascular and interstitial spaces of the brain. The details of this system, and its contribution to the delivery of nutrients and eliminating waste products, are yet to be established. Here we present a tailored MRI phantom to simulate the fluid dynamics of the CSF in the perivascular space. This glymphatic ultra-slow flow phantom facilitates testing of MRI flow measurements in a controlled environment, enabling optimization of MRI scan parameters to allow accurate measurements of glymphatic flow in the human brain.

3358		Reaching low-gadolinium concentration detection through sequences optimization on a dedicated phantom
		Emilie Poirion¹, Corentine Marie², Marine Boudot de La Motte³, Chloé Dupont⁴, Jean-Claude Sadik¹, and Julien Savatovsky¹
		¹Hospital Foundation A. de Rothschild, Imaging department, Paris, France, PARIS, France, ²Sorbonne University, Paris Brain Institute, Paris, France, Paris, France, ³Hospital Foundation Rothschild,Neurology department, Paris, France, Paris, France, ⁴Hospital Foundation A. de Rothschild, Pharmaceutical department, Paris, France, PARIS, France
		Gadolinium-enhanced imaging provides valuable information in clinical practice for the diagnosis of several diseases. Conventional sequences fail to detect low concentrations of gadolinium, such as those encountered in abnormal meninges. We designed a phantom containing 16 diluted gadobutrol tubes to compare and optimize sequences, based on normalized signal and contrast-to-noise ratio, for each gadolinium concentration. We performed a preliminary study comparing T1, FLAIR and FLAIR with optimized parameters on this phantom. The optimized FLAIR sequence shows an efficient detection of low concentrations, with a higher CNR than other sequences. Preliminary in-vivo experiment shows promising results for leptomeningeal abnomalities detection.

3359		Commercially available astriction cotton as a anisotropic DTI phantom: Comparisons with a hand-bundled fibers and a glass capillary plate
		Koji Sakai¹, Yasuhiko Tachibana², Toshiaki Nakagawa³, Hiroyasu Ikeno³, Takayuki Obata², and Kei Yamada¹
		¹Kyoto Prefectural University of Medicine, Kyoto, Japan, ²National Institute of Radiological Sciences, Chiba, Japan, ³Kyoto Prefectural University of Medicine Hospital, Kyoto, Japan
		We compared DTI measures among three different anisotropic diffusion phantoms: a commercially available astriction cotton; a glass capillary plate; a hand-bundled polyethylene fibers. The purpose of this study was to examine whether the cotton is useful as an anisotropic diffusion phantom. Differences in ADC and FA were evaluated by comparing coefficients of variation (CVs). No significant difference was seen for the largest eigen value: 2.06 - 2.14 x 10^-3 mm²/sec. Clear differences in FA were seen among the three DTI phantoms (p = 0.0079). CVs from five acquisitions for ADC and FA from every phantoms were all less than 2%.

3360		OpenCV based RF field mapping for MR coil assessment
		Egor Kretov¹, Zhao Kaixuan ^1,2, Charles Grassin³, and Thoralf Niendorf¹
		¹Max Delbrück Center for Molecular Medicine, Berlin, Germany, ²School of Biomedical Engineering, Southern Medical University, Guangzhou, China, ³Independent Researcher, Paris, France
		This work presents a cost-effective near-field RF mapping approach for accurate tracking of a field probe. The method is based on the OpenCV library. It serves as a practical tool for the rapid assessment and characterization of MR coils and arrays. The only equipment required for the setup is a field probe, a regular webcam, and a paper QR code label, which renders this technique highly accessible and easy-to-use.

3361		A Simple Device for Real-Time Detection of Head and Body Movements in a Mock Scanner, for Screening and Training Subjects
		Fadi Ayad¹ and Amir Shmuel²
		¹Biomedical Engineering, McGill University, Montreal, QC, Canada, ²McConnell Brain Imaging Centre, Montreal Neurological Institute, Montreal, QC, Canada
		Head and body movements introduce artifacts in structural, diffusion, and functional MRI. With the advent of imaging at ultra-high field, head and body movements limit our capacity to obtain high-resolution, high-quality data. We have developed a small wearable device for acquiring data on head and body movements and transmitting it wirelessly to a computer for real-time analysis while a subject is trained in a mock MRI scanner. This device works in parallel to an in-bore camera used for movement detection, to support subject screening and training to remain still in preparation for MRI.

3362		3-plane Localizer-aided Background Removal in Magnetic Resonance (MR) Images Using Deep Learning
		Apoorva Agarwal¹, Megha Goel¹, and Jignesh Dholakia¹
		¹GE Healthcare, Bengaluru, India
		This study presents a new Deep-Learning (DL) based strategy for background computation in MR images. 3-plane Localizer scans have been used for background-subtraction in all subsequent scans of same MR Examination. This is accomplished by obtaining foreground-background masks for Localizer images using U-Net model and applying Image Resampling techniques on the obtained mask to compute background for subsequent scans. Comparison with existing algorithms demonstrates that proposed method prevails in accuracy, effectiveness and provides improved visual contrast. It can also be used universally across anatomies and MR pulse-sequences as opposed to other methods requiring anatomy/sequence-specific tuning and adaptive parameter adjustments.

3363		Phantom Experiments for Optimal Soft Gating Parameter in Free-Breathing Hepatobiliary Phase MRI with KWIC Reconstruction
		Tomohiro Noda¹, Keitaro Sofue², Ryuji Shimada¹, Yuichiro Somiya¹, Shintaro Horii¹, Yoshiko Ueno², Naoki Yoshida¹, Yu Ueda³, Akiko Kusaka¹, and Takamichi Murakami²
		¹Center of Radiology and Radiation Oncology, Kobe University Hospital, Kobe, Japan, ²Department of Radiology, Kobe University Graduate School of Medicine, Kobe, Japan, ³Philips Japan MR Clinical Science, Tokyo, Japan
		In free-breathing radial k-space sampling with KWIC reconstruction, soft gating method can be adopted to reduce motion artifacts. We investigated optimal soft gating parameters for free-breathing hepatobiliary phase MRI. A programmable respiratory motion phantom with varying motion distance of 10, 20, 30 mm was imaged using six values of soft gating factor (SGF). Image contrast and sharpness were analyzed by calculating contrast ratio (CR) and full width at half maximum (FWHM). The CR and FWHM were not inferior compared with the reference standard images in any of the motion distances when the SGF was set at more than 1.4.

3364		A phantom-based method for MRI relaxation time mapping data validation and harmonization
		Davide Cicolari¹, Domenico Lizio², Patrizia Pedrotti³, Monica Teresa Moioli², Alessandro Lascialfari¹, Manuel Mariani¹, and Alberto Torresin^2,4
		¹Department of Physics, University of Pavia, Pavia, Italy, ²Department of Medical Physics, ASST Grande Ospedale Metropolitano Niguarda, Milan, Italy, ³Department of Cardiology, ASST Grande Ospedale Metropolitano Niguarda, Milan, Italy, ⁴Department of Physics, University of Milan, Milan, Italy
		A method for the MRI relaxation time measurement validation and harmonization is proposed: it relies on a phantom composed of vials filled with different concentrations of MnCl₂ aqueous solutions, whose relaxation times are characterized as a function of both concentration and temperature, employing NMR techniques. The accuracy and the precision of fast mapping sequences developed for cardiac applications are better quantified through, respectively, the phantom characterization and the SD maps analysis. Scan-dependent recalibrations of the relaxation time maps can be performed relying on the ground-truth NMR values of the phantom, aiming to clinical intra- and inter-center harmonization.

MR-Guided Interventions: Devices & Applications

Interventional & Low-Field MRI

Engineering/Interventional/Safety

4005		Development and Evaluation of an MR-safe Interventional Catheter with Tunable MR Visibility and Radiopacity
		Bridget F Kilbride¹, Caroline D Jordan², Andrew Chu³, Dave Barry³, Kerstin Mueller⁴, Sinyeob Ahn⁴, Teri Moore⁵, Mark W Wilson⁵, and Steven W Hetts⁵
		¹Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, ²Texas A&M University, Houston, TX, United States, ³Penumbra, Inc., Alameda, CA, United States, ⁴Siemens Medical Solutions, Malvern, PA, United States, ⁵University of California San Francisco, San Francisco, CA, United States
		Interventional MRI catheter-based procedures are greatly limited by current devices and their safety profiles, and next-generation MR-safe devices are still in development. We designed and evaluated a polymeric catheter concept that is both safe and visible in MRI and X-ray environments. All imaging was done in a two-room hybrid angio-MR suite to demonstrate compatibility with next-generation image-guided procedures. In a phantom, we acquired GRE and TSE sequences at 3T and imaged on a clinical biplane angiographic system to quantitate MRI visibility and radiopacity, respectively. The catheters exhibited promising tracking characteristics under MRI and X-ray on a polymer-based catheter.

4006		Optimized passive marker device visibility for MRI-guided endovascular interventions at 3T: a pulsatile flow phantom study
		Han Nijsink¹, Kristian G. Overduin¹, Sytse F. De Jong¹, Paul J.A. Borm², Torben Pätz³, Dennis G.H. Bosboom⁴, Michiel C. Warlé¹, and Jurgen J. Fütterer¹
		¹Radboudumc, Nijmegen, Netherlands, ²Nano4Imaging, Düsseldorf, Germany, ³Fraunhover MEVIS, Bremen, Germany, ⁴Soteria Medical B.V., Arnhem, Netherlands
		MRI-guidance for endovascular interventions is only eligible with clearly visible endovascular devices. Hence, we quantitatively and qualitatively evaluated marker visibility and artifact size of passive marker guidewires for different MRI sequence types, MRI parameters and marker concentrations at 3T MRI using a pulsatile flow phantom. Artifact size was positively correlated with TE and marker concentration and was significantly larger for bSSFP images compared to GRE images. The GRE images outperformed the bSSFP images in the quantitative image quality assessment. In conclusion, markers were adequately visible in GRE images and artifact visibility can be optimized by adjusting TE and marker concentration.

4007		MRI Needle Tracking with Phase-only Cross-Correlation (POCC) in the Presence of Susceptibility Artifacts
		Andreas Reichert¹ and Michael Bock¹
		¹Department of Radiology, Medical Physics, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
		The phase-only cross correlation (POCC) algorithm can be used to accurately detect the orientation of a passive needle guide in needle interventions. A POCC sequence continuously visualizes the planned needle pathway during needle guide movement. The insertion of a needle into the needle guide, however, degrades the POCC detection because of susceptibility artifacts. In this work, susceptibility artifacts of a needle are measured and simulated, and a potential integration integrated into the POCC algorithm is evaluated.

4008		4-DoF Needle-Guide Manipulator System for Interactive Real-Time MRI-Guided Prostate Interventions
		Junichi Tokuda^1,2, Pedro Moreira^1,2, Amanda Aleong³, Franklin King¹, John P Grimble⁴, Kemal Tuncali^1,2, Ravi Seethamraju⁵, Gerald Moran⁶, Himanshu Bhat⁵, Nick V Iftimia⁴, and Jesung Park⁴
		¹Radiology, Brigham and Women's Hospital, Boston, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³University of Toronto, Toronto, ON, Canada, ⁴Physical Science Inc., Andover, MA, United States, ⁵Siemens Medical Solutions USA Inc., Boston, MA, United States, ⁶Siemens Healthcare Ltd., Oakville, ON, Canada
		Accurate needle placement is crucial for MRI-guided targeted prostate biopsy. However, needle placement accuracy is often affected by the deviation of the needle caused by the anatomical structures on the needle path. To avoid anatomical structures that are likely to cause significant needle deviation, we developed a 4-degree-of-freedom (DoF) needle-guide manipulator system named “Smart Template”. The Smart Template allows physicians to insert a needle accurately to the target while monitoring the needle through interactive real-time MRI. We performed a preliminary evaluation of the device to test the feasibility of needle placement using Smart Template.

4009		An MR-Tracked Metallic injection needle for Distancing Radiation-sources from Sensitive tissues: Construct and Initial testing in Swine
		Ehud Jeruham Schmidt¹, Marc Morcos², Anthony Gunderman³, Junichi Tokuda⁴, Ravi Teja Seethamraju⁵, Luca Neri¹, Carmen Kut², Henry R. Halperin¹, Akila Ninette Viswanathan², and Yue Chen³
		¹Medicine (Cardiology), Johns Hopkins School of Medicine, Baltimore, MD, United States, ²Radiation Oncology, Johns Hopkins School of Medicine, Baltimore, MD, United States, ³Mechanical Engineering, University of Arkansas, Fayetteville, AR, United States, ⁴Radiology, Brigham and Women's Hospital, Boston, MA, United States, ⁵Siemens Medical Solutions, Boston, MA, United States
		A metallic actively-tracked injection needle was constructed for purposes of reducing dose to normal tissues surrounding irradiated tumors in cervical cancer and prostate cancer radiation therapy. Hydrogel is injected into tissue or anatomic cavities between the tumor and normal tissues, increasing the distance from the radiation source. The needle was tested in a gynecological phantom and in swine. It provided 1.2x1.2x1.2mm³ targeting precision @16 frames-per-second navigation, supporting rapid navigation speeds currently possible only under X-ray or Ultrasound guidance. The injected topology over time was visualized during injection, allowing creation of more uniform dose-shielding regions.

4010		Attenuation of the dark band artifact in MR-guided focused ultrasound using an ultra-flexible high-sensitivity head coil
		Isabelle Saniour¹, Fraser Robb², Victor Taracila², Henning U. Voss¹, Michael G. Kaplitt³, J. Levi Chazen¹, and Simone Angela Winkler¹
		¹Department of Radiology, Weill Cornell Medicine, New York, NY, United States, ²MR Engineering, GE Healthcare, Aurora, OH, United States, ³Department of Neurological Surgery, Weill Cornell Medicine, New york, NY, United States
		Transcranial magnetic resonance guided focused ultrasound (MRgFUS) has shown dramatic success in the treatment of various neurodegenerative diseases. However, black band artifacts arise in MR images due to the high-permittivity water bath and the metallically lined helmet-shaped transducer together with the vendor-installed body coil. In this work, we present electromagnetic simulations of a very thin, flexible, and acoustic transparent head coil design (FUS-Flex). Simulations show a signal-to-noise-ratio (SNR) increase of 3.5× and 5× compared to a body coil with and without the transducer, respectively, and an attenuation of the black band artifact in the regions of interest.

4011		MR guided Focused Ultrasound as a Non-Invasive Surgical Treatment of Lung Cancer
		Jaime Mata¹, Lauren Powlovich², David Moore², and Linda Martin¹
		¹University of Virginia, Charlottesville, VA, United States, ²Focused Ultrasound Foundation, Charlottesville, VA, United States
		Malignant lung cancer carries a poor prognosis with a 5-year survival rate of about 18%. This new method proposes an innovative minimally invasive procedure for the transcutaneous ablation of lung tumor masses with complete removal or significant debulking of the masses. This new procedure could increase lung cancer survival rates and at the same time decrease morbidity and side effects associated with current treatment therapies. It will also provide a viable treatment for a large group of patients that cannot tolerate resection surgery, radiotherapy and chemotherapy, or who have had prior radiation and cannot have additional radiation to that region.

4012		Comparison of Diffusion Tractography and fMRI-based Targeting for MRgFUS Treatment of Essential Tremor
		Kristin Quah¹, Jonathan Samuel Goodman², Gustavo Loo Kang Chau³, Kim Butts Pauly⁴, Pejman Ghanouni⁴, Gary Glover⁴, and Jennifer McNab⁴
		¹Electrical Engineering, Stanford University, Stanford, CA, United States, ²Biophysics, Stanford University, Stanford, CA, United States, ³Bioengineering, Stanford University, Stanford, CA, United States, ⁴Radiology, Stanford University, Stanford, CA, United States
		Probabilistic diffusion tractography and fMRI are two alternative methods for targeting the ventral intermediate nucleus of the thalamus in patients with essential tremor (ET) for treatment with transcranial magnetic resonance imaging-guided focused ultrasound (tcMRgFUS). In this study, three ET subjects underwent MRgFUS thalamotomy with traditional targeting using anatomic landmarks. Tractography and fMRI targeting were compared retrospectively to determine how they relate to one another and to the targets selected by the surgeon. Two of the three subjects showed a consistent spatial relationship between fMRI, tractography and anatomical targets.

4013		Comparison of birdcage resonator designs for clinical MR-guided radiotherapy
		Kilian A. Dietrich^1,2, Sebastian Klüter², Benjamin R. Knowles¹, Jürgen Debus^2,3, Markus E. Ladd^1,3, and Tanja Platt¹
		¹Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Radiation Oncology, University Hospital, Heidelberg, Germany, ³Faculty of Medicine, Heidelberg University, Heidelberg, Germany
		Electromagnetic field simulations were performed at 0.345T and 1.5T to find an advantageous RF coil design for typical scanners in MR-guided therapy. Hence, different birdcage coil designs were characterized and compared with one another with respect to their corresponding transmit and receive field characteristics.

4014		Feasibility of free breathing real-time cine-MRI for MR-guided Cardiac Radioablation on the Unity MR-linac
		Osman Akdag¹, Stefano Mandija¹, Pim Borman¹, Eveline Alberts², and Martin Fast¹
		¹Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands, ²Philips Healthcare, Best, Netherlands
		Stereotactic arrhythmia radioablation (STAR) is a novel non-invasive treatment technique for ventricular tachycardia patients, refractory to conventional catheter ablation. Here, we investigate the feasibility of integrating real-time, free-breathing, cardiac cine-MRI into the STAR radiotherapy workflow. As a first step towards MRI-guided STAR treatments, we test our imaging approach on a diagnostic 1.5T MRI-simulator (Philips, Ingenia), and on a 1.5T Elekta Unity MR-linac. Our results indicate the feasibility of acquiring real-time, free-breathing, cine MRI images on both systems at 14Hz, enabling real-time motion assessment and delivery adaptation without additional cardiac imaging hardware.

4015		Clinical evaluation of 4DMRI for lung cancer radiation treatment planning
		Jonathan Goodwin^1,2, Satomi Higuchi¹, Laura O'Connor^1,2, Amy Zafara¹, Kate Skehan¹, Terry Perkins³, Sanjiv Gupta¹, Peter Greer^1,2, Jane Ludbrook^1,2, and John Simpson^1,2
		¹Calvary Mater Hospital, Newcastle, Australia, ²Univeristy of Newcastle, Newcastle, Australia, ³Blacktown Cancer & Haematology Centre, Blacktown, Australia
		4D-CT is routinely acquired for lung cancer treatment planning to visualise the extent of tumour motion, to determine the appropriate treatment target volume. However, it can be unreliable in cases of irregular breathing, is susceptible to image artefact in regions close to the diaphragm, and shows generally poor soft tissue contrast. In this study we evaluated an alternative self-navigating 4D-MRI approach in terms of motion detection accuracy, measured tumour volume, and dosimetric differences observed with respect to patients’ existing lung cancer treatment plans.

4016		MR SIGnature MAtching (MRSIGMA) with retrospective self-validation for real-time volumetric tumor motion imaging
		Nathanael Kim¹, Kathryn Tringale², Christopher Crane², Neelam Tyagi¹, and Ricardo Otazo^1,3
		¹Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ²Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ³Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, United States
		MRSIGMA is a promising real-time volumetric imaging for MRI-guided adaptive radiotherapy using a MR-Linac system. However, the lack of a real-time 3D reference image acquired with similar temporal resolution introduces significant challenges for in vivo validation. This work proposes a retrospective self-validation for MRSIGMA, where the same data used for real-time imaging are used to create a non-real-time reference. MRSIGMA with self-validation is tested in patients with liver tumors using quantitative metrics defined on the tumor and nearby organs-at-risk structures.

4017		Investigation of A Fast-volumetric Four-dimensional Magnetic Resonance Imaging Technique for Abdominal Radiotherapy Tumor Motion Management
		Tian Li¹, Haonan Xiao¹, Ge Ren¹, Weiwei Liu², Yibao Zhang², Hao Wu², Weihu Wang², and Jing Cai¹
		¹Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, Hong Kong, ²Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Beijing Cancer Hospital & Institute, Peking University Cancer Hospital & Institute, Beijing, China, Beijing, China
		Motion management plays an important role in abdominal cancer radiotherapy. Current motion measurement method using 2D Cine MRI is inefficient. However, there is no commercial four-dimensional MRI available for motion management. In this study, we aim to investigate a fast-volumetric four-dimensional MRI technique using commercial sequence for tumor motion management in liver cancer patient. Our preliminary results shown that the commercially available TWIST-VIBE 4D-MRI sequence is capable of measuring liver tumor motion accurately with an acceptable tumor contrast.

4018		Subject-specific positional probability volume mapping for internal target volume determination in Radiotherapy
		Oi Lei Wong¹, Jing Yuan¹, Darren MC Poon², Yi Hang Zhou¹, Siu Ki Yu¹, and Kin Yin Cheung¹
		¹Medical Physics and Research, Hong Kong Sanatorium, Hong Kong, Hong Kong, ²Comprehensive Oncology Center, Hong Kong Sanatorium, Hong Kong, Hong Kong
		A novel ITV determination technique based on the volume of positional probability distribution (PPV) generated by volumetric 4DMRI was proposed and verified on cancer patients. For large targets, both PPV and 4D-CT generated ITV were similar with relatively large DSC. For small targets, however, relatively small DSC was observed, where poor tumor visibility in 4D-CT may be the cause.

4019		Promising results using synthetic CT for 2D and 3D patient positioning in head and neck radiotherapy
		Emilia Palmér¹, Fredrik Nordström^1,2, Anna Karlsson^1,2, Karin Petruson³, Maria Ljungberg^1,2, and Maja Sohlin^1,2
		¹Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden, ²Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden, ³Department of Oncology and Radiotherapy, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
		In an MRI-only radiotherapy workflow, in addition to enabling absorbed dose calculation the generated synthetic CT (sCT) must also be valid for patient positioning at treatment course. To evaluate MRI-only patient positioning for head and neck cancer patients, fourteen 3D cone beam CTs were retrospectively registered to CT and sCT. Further, original Digital Reconstructed radiographs originating from the CT and synthetic Digital Reconstructed radiographs originating from the sCT, were retrospectively registered to orthogonal projections. The small mean difference between the registrations showed that sCT could replace the CT for both 3D and 2D head and neck radiotherapy patient positioning.

4020		Damping acoustic noise for MRI in Radiotherapy Settings
		Erik R Huijing¹, Femke Wetzels¹, Edwin Versteeg¹, Koenraad Rhebergen¹, Simon Woodings¹, Dennis Klomp¹, Marielle Philippens¹, Nico van den Berg², and Stefano Mandija³
		¹UMC Utrecht, Utrecht, Netherlands, ²Computational Imaging Group for MR Diagnostic & Therapy, UMC Utrecht, Utrecht, Netherlands, ³Computational Imaging Group for MR Diagnostic & Therapy, University Medical Center Utrecht, Utrecht, Netherlands
		We present two hoods for acoustic noise damping for MRI in Radiotherapy. This is especially relevant for brain and head-and-neck patients who are scanned repetitively inside immobilization masks, which prevent wearing all the required earing protection devices. The hoods show good noise damping (average at least 10 dB attenuation) and minimal radiation dose attenuation (<1%), making them suitable also for MR-linac systems. Subjective results from a survey on 15 volunteers show that the hoods are well tolerated and do not increase significantly the feeling of claustrophobia.

4021		UTE-MRI complements CT in bone characterization for improved proton therapy dose calculation
		Xin Miao¹, Raanan Marants², Thomas Benkert³, Evangelia Kaza², Jeremy Bredfeldt², and Atchar Sudhyadhom²
		¹Siemens Medical Solutions USA Inc., Boston, MA, United States, ²Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center, Boston, MA, United States, ³Siemens Healthcare GmbH, Erlangen, Germany
		CT-based proton therapy dose calculation suffers from significant uncertainties that critically limit clinical efficacy. Previous works demonstrated improved proton range calculation by combining quantitative MRI with CT. This study extends those works into bone, a challenging region for tissue characterization. CT and a novel UTE MRI technique were used to investigate their complimentary information for bone characterization. Both phantom and in vivo experiments showed that combining UTE-MRI and CT measurements achieved accurate classification of bone types. Understanding of bone types can have significant implications on the determination of bone tissue composition and, ultimately, accuracy of radiation delivery in proton therapy.

4022		Magnetic Resonance Guided Percutaneous Cryoablation of Extra-abdominal Desmoid Tumors: An Institutional Experience
		Ali Agely¹, Vipul Sheth¹, Pejman Ghanouni¹, and Ryan L. Brunsing¹
		¹Radiology, Stanford University, Palo Alto, CA, United States
		Desmoid tumors are challenging to control with chemotherapy, surgery, or radiation. This retrospective review evaluated patients with extra-abdominal desmoid tumors treated with MR-guided cryoablation at our institution over two years. The primary endpoint was tumor volume change before and 3 months after cryoablation; the secondary endpoint was the change in health status assessed at the same interval. Our study demonstrates MR-guided cryoablation results in the reduction of both tumor size and improvement in health status scores. No severe adverse events occurred. We conclude that MR-guided cryoablation is an effective and safe treatment option for desmoid tumors.

4023		PET/MRI Assessment of 90Yttrium Prostate Localization and Acute Response Following Intra-arterial Radioembolization in A Canine Model
		Weiguo Li^1,2, Kathleen Harris¹, Amrutha Mylarapu¹, Malcolm Burks¹, Simone Raiter¹, Vanessa Louise Gates¹, Andrew Gordon¹, Robert Lewandowski¹, Riad Salem¹, and Samdeep Mouli¹
		¹Radiology, Northwestern University, Chicago, IL, United States, ²Bioengineering, University of Illinois at Chicago, Chicago, IL, United States
		Local-regional therapy of prostate cancer with ⁹⁰Yttrium (⁹⁰Y) radioembolization is a novel radiotherapy approach that delivers high-dose radiation therapy with minimal non-target radiation. However, currently no accurate way exists to evaluate radiation effects noninvasively following embolization. In this study, we sought to apply PET/MRI to assess biodistribution of ⁹⁰Y and estimate effects of treatment following ⁹⁰Y prostate artery radioembolization in a dog prostate model.

4024		Improved therapy planning for eye tumours: a tumour geometry comparison between MRI and conventional ultrasound
		L. Klaassen^1,2, M.G. Jaarsma-Coes^1,2, T.A. Ferreira², T.H.K. Vu¹, M. Marinkovic¹, C.R.N. Rasch³, G.P.M. Luyten¹, and J.W.M. Beenakker^1,2
		¹Department of Ophthalmology, LUMC, Leiden, Netherlands, ²Department of Radiology, LUMC, Leiden, Netherlands, ³Department of Radiotherapy, LUMC, Leiden, Netherlands
		Ocular magnetic resonance imaging, enabling 3D tumour imaging and providing better soft tissue contrast than conventional ultrasound, is increasingly used for uveal melanoma. The aim of this research was to determine the difference in geometrical tumour measurements between ultrasound and MRI. For this purpose, tumour prominence and largest basal diameter were calculated automatically based on MR imaging and compared to the US measurements. Differences >0.5mm were observed in 55% of prominence measurements and 80% of LBD measurements. Furthermore, automatically measuring tumour geometry based on 3D MR imaging lead to the discovery of inconsistencies in measurement definitions within and across disciplines.

Engineering & Applying Low-Field MRI

Interventional & Low-Field MRI

Engineering/Interventional/Safety

4025		Low-Field Point-of-Care MRI: Automated Estimates of Brain Midline Shift Correlate With Clinical Outcomes in Stroke
		Prantik Kundu¹, Sadegh M. Salehi¹, Bradley A. Cahn², Mercy H. Mazurek², Matthew M. Yuen², Jo Schlemper¹, Barbara Gordon-Kundu², Rafael O'Halloran¹, Michal Sofka¹, and Kevin N. Sheth²
		¹Hyperfine Research Inc., Guilford, CT, United States, ²Yale University School of Medicine, New Haven, CT, United States
		Low-field (64 mT) point-of-care (POC)-MRI was acquired at the bedside from patients with ischemic and hemorrhagic stroke in the neurointensive care unit at a major academic medical center (n=128). An AI system was trained to quantify brain midline shift (MLS), a standard neuroradiological marker of brain injury from POC-MRI, using anatomical annotations from independent neuroradiologists. A cross-validation experiment showed that AI estimates of MLS from POC-MRI were associated with stroke severity and disability at subsequent discharge. AI estimates of MLS greater than 1.5 mm were positively predictive of poor discharge outcome in the full sample and in ischemic stroke.

4026		Reliability of brain volumetrics in low-field portable MRI
		Thomas Campbell Arnold¹, Ramya Muthukrishnan², Steven N Baldassano¹, Samantha By³, Brian Welch³, Brian Litt^1,4, and Joel M. Stein⁵
		¹Bioengineering, University of Pennsylvania, Philadelphia, PA, United States, ²Computer Science, University of Pennsylvania, Philadelphia, PA, United States, ³Hyperfine Research, Guilford, CT, United States, ⁴Neurology, Perelman School of Medicine, Philadelphia, PA, United States, ⁵Radiology, Perelman School of Medicine, Philadelphia, PA, United States
		A growing body of literature demonstrates the value of MRI-based volumetric measures in diagnosing and treating neurodegenerative disorders. However, clinicians cannot offer biomarker screening for at-risk patients due to MRI systems’ high cost and limited access. Low-field MRI scanners offer a potential method for collecting low-cost images that could be analyzed for longitudinal biomarker changes or used in population-level studies. Here we examine the reliability of volumetric measurements made on a low-field MRI system. We compare the variability of 6 tissue volumes collected over 40 scans for 3T and 64mT systems, as well as the overlap between volume segmentations.

4027		Feasibility of human in vivo skeletal muscle and cardiac proton spectroscopy at 0.75T
		Sophie M. Peereboom¹, Christian Guenthner¹, Mohammed M. Albannay¹, and Sebastian Kozerke¹
		¹Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
		Proton MR spectroscopy can assess cardiac triglyceride levels. Although spectral separation and thermal polarization decrease at lower field strength, increased T₂^* and T₂ values, decreased T₁ values, decreased echo times and the possibility to decrease receiver bandwidth are clear advantages compared to higher fields. In this work the feasibility of in vivo skeletal muscle and cardiac proton spectroscopy at 0.75T is demonstrated. For this purpose, a clinical 3T Philips Achieva scanner was ramped down to a field strength of 0.75T. Results are compared to spectra acquired at 1.5T and 3T and simulations confirm experimental findings.

4028		Novel Technique for Assessment of Patellar Tracking During Weight-Bearing Knee Flexion Using Dynamic Upright MRI
		Neeraj Kulkarni¹, John Greenhalgh¹, Robert Wolf¹, David Chu¹, Rachel Caffrey², Brianna Elizabeth Damadian¹, and Raymond Damadian¹
		¹FONAR Corporation, Melville, NY, United States, ²Lehigh University, Bethlehem, PA, United States
		Despite decades of imaging research focused on the knee, little attention has been paid to dynamic, weight-bearing knee MRI emulating the physiologic condition of the joint. Here, we utilize dynamic imaging in alternating axial and sagittal planes to capture the patellofemoral joint of one volunteer performing one cycle of knee flexion/extension. Our findings indicate that it is possible to characterize patellar tracking in both axial and sagittal planes utilizing fast imaging sequences (<2 minutes) on mid-field upright MRI. Additionally, it is possible to quantify the patellofemoral kinematics on these images using patellar flexion angle and anteroposterior patellar translation.

4029		A Novel Dedicated 0.35T Open Neonatal-Infant Brain MRI system
		Mao Sheng¹, ZhongChang Miao², Jian Bao³, Renjie Zong³, SiSeung Kim³, Huiyao Zhang³, and Bing Keong Li³
		¹Department of Radiology, Children’s Hospital of Soochow University, Suzhou, China, ²Department of Radiology, The First People’s Hospital of Lianyungang, Jiangsu Province, China, ³Jiangsu LiCi Medical Device Co., Ltd, Lianyungang, China
		A dedicated 0.35T Neonatal-Infant Brain MRI system is developed to investigate the effectiveness and safeness for neonatal and infant patients. 66 volunteers from 0-12 months are recruited to undergo a clinical trial and it is found that low field brain images displayed high grey-white tissue contrast, which is notably helpful for clinical diagnosis. The newly developed system also has very low acoustic noise and that most of the volunteer showed no sign of temperature raise. Low field MRI system therefore has the potential to be a effective and safer alternative MRI system for neonatal and infant patients.

4030		In vivo human imaging on a 47.5mT open MRI system with active Electromagnetic Interference (EMI) mitigation using an electrode
		Sai Abitha Srinivas^1,2, Stephen Cauley^3,4, Jason P Stockmann^3,4, Charlotte R Sappo^1,2, Christopher E Vaughn^1,2, Lawrence L Wald^3,4,5, William A Grissom^1,2,6,7, and Clarissa Zimmermann Cooley^3,4
		¹Vanderbilt University Institute of imaging science, Nashville, TN, United States, ²Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ³Harvard Medical School, Boston, MA, United States, ⁴Dept. of Radiology, Massachusetts General Hospital, Athinoula A Martinos Center for Biomedical Imaging, Boston, MA, United States, ⁵Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States, ⁶Department of Electrical Engineering, Vanderbilt University, Nashville, TN, United States, ⁷Department of Radiology, Vanderbilt University, Nashville, TN, United States
		Low-field MRI scanners can operate outside MR safe rooms, but their image quality is adversely affected due to the presence of electromagnetic interference signals which can severely obscure the images. We demonstrate a generalized dynamic model that can handle time-varying external interference sources by using simultaneously acquired data from multiple EMI detectors - specifically from an electrode, traditional RF pick up coils and the primary MR coil - in-vivo, in real world EMI settings on a 47.5mT permanent magnet open MRI system.

4031		Design of a portable, low-field magnetic resonance sensor for clinical measurement of volemic status
		Sydney Sherman^1,2 and Michael Cima^2,3
		¹Health Science and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, ²Koch Institute for Integrative Cancer Research, Cambridge, MA, United States, ³Massachusetts Institute of Technology, Cambridge, MA, United States
		A low-field portable MR-based sensor was designed for the acquisition of clinical T2 relaxometry measurements in skeletal muscle. A range of low-field permanent magnet array configurations were modeled with varying sensitive region depths and homogeneous volumes; an optimization score for each design was calculated. The optimal design has a sensitive region 15-20mm from the surface of the magnet, making it capable of acquiring measurements deep into the leg such that the measurement is fully localized to skeletal muscle. The exclusion of subcutaneous fat tissue in the sensitive region will improve sensitivity to fluid shifts within the skeletal muscle.

4032		In vivo hypoxia monitoring using a novel single sided NMR device
		Dion G Thomas¹, Freya G Harrison², Paul D Teal³, Petrik Galvosas^1,4, Mary J Berry^2,5, Sergei Obruchkov⁶, and Yu-Chieh Tzeng²
		¹School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand, ²Centre for Translational Physiology, University of Otago, Wellington, New Zealand, ³School of Engineering and Computer Science, Victoria University of Wellington, Wellington, New Zealand, ⁴MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand, ⁵Department of Paediatrics and Child Health, University of Otago, Wellington, New Zealand, ⁶Robinson Research Institute, Victoria University of Wellington, Wellington, New Zealand
		In this study, we investigate how a low field single-sided NMR device can be used to monitor brain tissue properties in-vivo. This device produces a B₀ field with a sweet spot in the brain, which defines the region of tissue that is measured. An ovine model of brain hypoxia was developed, to allow tissue oxygenation to be controlled. We observed that the T₂ decreased during hypoxia, recovering once normal oxygenation levels were re-established. These results shows that single-sided NMR devices have the potential to be used for real-time monitoring applications.

4033		Zero-Dead-Time Earth’s Field NMR Using Two-Photon Excitation
		Victor Han¹ and Chunlei Liu^1,2
		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
		Two-photon excitation allows for excitation at half of the Larmor frequency. In Earth’s magnetic field, this corresponds to a Larmor frequency of about 2 kHz and an excitation frequency of about 1 kHz. By transmitting at 1 kHz and receiving at 2 kHz, we could transmit and receive at the same time by using filters to protect the receiver. While some harmonic distortion prevented us from fully separating the transmitted from the received signal during excitation, the always connected and unsaturated receive circuitry allowed us to eliminate receiver dead time, which can be quite long at low frequencies.

4034		An axial gradient coil with improved linearity for Halbach-based MR systems
		Bart de Vos¹, Thomas O'Reilly¹, Wouter Teeuwisse¹, Rob Remis², and Andrew Webb¹
		¹C.J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands, ²Circuits and Systems, Delft University of Technology, Delft, Netherlands
		We reduced image artifacts and increased the attainable axial field-of-view by designing a highly linear x-gradient coil for Halbach array-based MR systems. A truncated sum of sinusoidal basis function is used for the current density. Higher order modes combined with specifying the target field inside a volume lead to a stable solution of the inverse source problem. The coil was installed on our 50 mT system and resulted in a 150% increase in linear DSV with respect to our previously designed gradient coil. Whole-brain three-dimensional images have been acquired using turbo spin echo sequences in less than 10 minutes.

4035		A Linear Gradient Solenoid for Slice-Selective Brain Imaging using B1+-Selective RF Pulses
		Matthew Wilcox^1,2, Sai Abitha Srinivas^1,2, Christopher E Vaughn^1,2, Charlotte R. Sappo^1,2, and William A. Grissom^1,2,3,4
		¹Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ³Radiology, Vanderbilt University, Nashville, TN, United States, ⁴Electrical Engineering, Vanderbilt University, Nashville, TN, United States
		Despite drawbacks including production of acoustic noise and peripheral nerve simulation, long switching times, bulkiness, and high costs, use of B₀ gradient coils is ubiquitous in conventional MR imaging. Replacement of B₀ encoding with B₁⁺ encoding alleviates these concerns and allows the use of hardware which is lower-cost, more compact, and silent. As a first step towards realizing a full B₁⁺ encoding coil system, this work demonstrates an RF z-gradient solenoid coil developed for brain imaging on a 47.5 mT system. The coil performance is evaluated in simulation, bench, and scanner experiments and slice-selection using B₁⁺-selective pulses is demonstrated.

4036		Target-field optimized quadrature RF coils for wrist imaging on a 76 mT Halbach-based MR system
		Bart de Vos¹, Thomas O'Reilly¹, Wouter Teeuwisse¹, Rob Remis², and Andrew Webb¹
		¹C.J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands, ²Circuits and Systems, Delft University of Technology, Delft, Netherlands
		We describe a design method for quadrature RF coils for Halbach based magnets using a target field approach. The resulting current densities corresponding to these coils make them inherently decoupled. We constructed a coil pair for a newly built 76 mT system and imaged the wrist of a volunteer. The images showed a 33% SNR improvement over a linear coil, in close agreement with simulations.

4037		Design and testing of a four-channel receive array coil on a 50 mT permanent magnet system.
		Javad Parsa¹, Thomas O'Reilly¹, Bart de Vos¹, and Andrew Webb¹
		¹Leiden University Medical Center, Leiden, Netherlands
		An integrated transmit coil and four-element receive array has been simulated, constructed, characterized and tested on a low field MRI system operating at 2.15 MHz. Using a combination of loops and butterfly coils neighbouring inter-element coupling is below -18 dB, with directly opposite coils ~-9 dB, and <-17 dB coupling for all receive coils to the transmit coil. Images of a phantom have been acquired with a simple sum-of-squares reconstruction.

4038		Dipole position sensors integrated in receiver array for motion detection and correction
		Ed Boskamp¹, Mike Twieg¹, and Rafael O'Halloran¹
		¹Hyperfine, Guilford, CT, United States
		MRI is sensitive to patient motion. There are a number of pulse sequence techniques like navigators and propeller to prevent motion artifacts. We are introducing a sensitive sensor based technique to detect motion and pose without touching the patient. The sensors are a number of miniaturized dipole resonators integrated into the receiver array. Motion corrupted lines in k space are flagged and rescanned, or when motion is between a limited number of poses, the data can be binned and combined before the recon process.

4039		B0-shimming methodology for affordable, compact, and homogeneous low-field MR magnets
		Konstantin Wenzel¹, Hazem Alhamwey¹, Tom O'Reilly², Layla Riemann¹, and Lukas Winter¹
		¹Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany, ²Leiden University Medical Center (LUMC), Leiden, Netherlands
		In this work, B₀-shimming techniques are investigated allowing the construction of simple, low-cost, and homogeneous Halbach-based low-field MR magnets. The techniques are applied to build a desktop MR magnet at B₀=0.1T and can be easily scaled to magnet designs of larger diameter. The presented shimming approach improved B₀ homogeneity by a factor of ~8 from 5448ppm to 682ppm in a 2D target region. All design files and code concerning this work will be made available open source on www.opensourceimaging.org.

4040		The Development of a Digital-twin of a Permanent-Magnet-Array (PMA)-Based Portable MRI System
		Shao Ying Huang¹, Yi-Dan Chen¹, Ting-Ou Liang², Yan Hao Koh¹, and Wenwei Yu³
		¹Singapore University of Technology and Design, Singapore, Singapore, ²Zhejiang University, Hangzhou, China, ³Chiba University, Chiba, Japan
		This abstract presents the development of a digital-twin of a permanent-magnet-array-based portable MRI system. It is to guide the design, optimization, hardware debug and calibration, and evaluation of such a system at both a sub-system level and a system level. Meanwhile, it facilitates the development of a sub-system without building the whole system. It consists of the simulators for magnet array, RF coil, gradient coils, pulse sequence, k-space analysis, image reconstruction, and image quality evaluation.

4041		The design of a low-weight homogenous Halbach helmet for imaging the adult brain.
		Thomas O'Reilly¹ and Andrew Webb¹
		¹C.J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands
		Arrays of permanent magnets have shown promise as a relatively light weight, low cost, sustainable way of generating magnetic fields suitable for MRI. In this work we show the design of a new homogenous helmet shaped, Halbach-array based magnet optimized for imaging the adult head. The magnet has a mean magnetic field strength of 59.7 mT and a homogeneity of 1313 ppm over a brain sized 25x20x15 cm³ ellipsoid. By truncating one side of the magnet the weight of the system has been reduced compared to symmetric designs while increasing the obtained field strength.

4042		The role of non-random magnet rotations on main field homogeneity of permanent magnet assemblies
		Thomas O'Reilly¹ and Andrew Webb¹
		¹C.J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands
		Arrays of permanent magnets are an attractive approach to designing magnets for low field MRI systems as they are affordable, easy to handle and offer great flexibility in magnet designs. However, translating designs from simulations to realised systems is challenging. The difference between the two is often attributed to imperfections in the individual magnets that make up the permanent magnet array. Here we show that non-random errors in the magnet rotations due to imperfect magnet holders can be the dominant cause of this discrepancy and if the imperfections are known they can easily be corrected for during manufacturing.

4043		Triple-ring permanent magnet design for ultra-low-field MRI systems
		Yang Gao^1,2, Alex T. L. Leong^1,2, Yilong Liu^1,2, and Ed X. Wu^1,2
		¹Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China
		MRI has impacted modern healthcare tremendously. However, MRI accessibility is low and extremely inhomogeneous globally. The recent shift in prioritizing MRI’s value has seen the emergence in developing point-of-care systems at ultra-low-field (<0.1T), particularly the use of permanent magnets for its light-weight, low power and low cost benefits. However, fundamentally, a relatively strong and uniform magnetic field is still desired for ultra-low-field MRI systems. Here, we propose a triple-ring permanent magnet design that aims to preserve and improve upon the fundamental field homogeneity requirements of MR imaging at ultra-low-field, without sacrificing the flexibility to perform both body and head imaging.

4044		Educational Tabletop MRI system using the Open-Source Console for Real-time Acquisition (OCRA)
		Marcus Prier^1,2, David Schote^1,2, Ivan Fomin^1,2, Thomas Witzel³, Georg Rose^1,2, and Oliver Speck^1,2
		¹Otto-von-Guericke University, Magdeburg, Germany, ²Research Campus STIMULATE, Magdeburg, Germany, ³Q Bio Inc, San Carlos, CA, United States
		A Tabletop MRI system was developed that merges the Marinos Center Tabletop and OCRA projects, and is improved in many aspects compared to the original system. The proposed system includes a fully functional MRI console with a customizable GUI and microcontroller server. The hardware was extended with an optimized magnet design with passive shimming, active TR switches with reverse bias and RFPA noise blanking, and a low cost and fast response 4 channel gradient amplifier. It can be used for educational purposes and student courses in medical engineering.

MR-Guided Interventions: Methods

Interventional, Multimodal & Auxiliary Engineering

Engineering/Interventional/Safety

4242		Exploration of the Surgical Placement of the Local Pituitary Coil for Microadenomas
		Jiahao Lin^1,2, Siyuan Liu², Rock Hadley³, Marvin Bergsneider⁴, Giyarpuram N Prashant⁴, Sophie Peeters⁴, Robert Candler^2,5, and Kyunghyun Sung¹
		¹Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, LOS ANGELES, CA, United States, ²Department of Electrical and Computer Engineering, University of California, Los Angeles, LOS ANGELES, CA, United States, ³Department of Radiology, University of Utah, Salt Lake City, UT, United States, ⁴Department of Neurosurgery, University of California, Los Angeles, LOS ANGELES, CA, United States, ⁵California NanoSystems Institute, Los Angeles, CA, United States
		We construct an agar phantom to examine the SNR variation as the coil plane rotates from 0° to 90°, respect to B0. Our local pituitary coil has improved SNR with a factor, ranged from 3.3 to 4.2, compared to the commercial Siemens head coil as long as the surgical positioning of the coil to be within 0° and 70° with respect to the B0 field.

4243		Toward automatic lesion transmurality assessment using machine learning: a proof of concept in preclinical EP studies under MRI-guidance
		Valéry Ozenne^1,2,3,4, Pierre Bour^2,3,4, Marylène Delcey^2,3,4, Nicolas Cedilnik⁵, Maxime Sermesant⁵, and Bruno Quesson^2,3,4
		¹Centre de Résonance Magnétique des Systèmes Biologiques, UMR 5536, CNRS, Bordeaux, France, ²IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Bordeaux, France, ³Univ. Bordeaux, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France, ⁴INSERM, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France, ⁵Université Côte d’Azur, Inria, Epione, Sophia Antipolis, France
		MR-guidance of electrophysiological (EP) procedures requires manual segmentation of the cardiac cavities either at the beginning of the procedure to produce the roadmap volume or after radiofrequency ablation (RFA) to assess the lesion transmurality in post ablation images. The purpose of this work is to evaluate the feasibility of automatic in-line segmentation in the context of routine preclinical EP studies.

4244		Towards Catheter-based Intra-Arterial Spin Labeling for Perfusion Measurements
		Kevin Waescher¹, Simon Reiss¹, Ali Caglar Özen^1,2, Thomas Lottner¹, and Michael Bock¹
		¹Dept. of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, ²German Consortium for Translational Cancer Research Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany
		MR-guided catheterization with injection of Gd-based contrast agent allows for quantitative perfusion measurement of the myocardium in coronary interventions. However, Gd is contraindicated in patients with impaired renal function, and it changes the relaxation times in the target organ after injection, so that a characterization of the target tissue becomes difficult. In this study, we provide a different solution to quantify perfusion using arterial spin labelling with a catheter based coil. The results show that ASL using a local catheter based labelling coil provides an alternative technique for perfusion measurements during cardiovascular interventions without exogenous contrast agents.

4245		Prototype Platform for Real-time MR-guided Brain Clot Evacuation
		Robert Moskwa¹, Azam Ahmed², and Walter Block¹
		¹Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ²Neurological Surgery, University of Wisconsin-Madison, Madison, WI, United States
		The international Phase III MISTIE Trial, which used CT-image guidance to position a catheter at the site of intracerebral hemorrhage (ICH) failed to meet its clinical endpoint for all patients. The Trial concluded that improved guidance was needed to help a wider set of neurosurgeons. MR-guidance of ICH evacuation could meet these needs. We present an MR-guidance prototype to provide neurosurgeons with a real-time interface with similar viewpoints as commonly used in stereotactic operating room settings. The MR-guidance prototype shows potential to be a reliable tool to assist as monitoring and guiding tools and lysing drugs during clot-evacuation procedures.

4246		PETRA subtraction-based MRA to assess middle-cerebral-artery stenosis before and after treatment with angioplasty
		Feifei Zhang¹, Yuncai Ran¹, Shujian Li¹, Jinxia Zhu², Xuemei Gao¹, Jingliang Cheng¹, and Chengcheng Zhu³
		¹The first Affiliated Hospital of Zhengzhou University, Zhengzhou, China, Zhengzhou, China, ²MR Collaboration, Siemens Healthcare Ltd., Beijing, China, Beijing, China, ³Department of Radiology, University of Washington, Seattle, Seattle, WA, United States
		This study investigated the feasibility of PETRA-MRA to evaluate stent angioplasty of middle-cerebral-artery stenosis before and after treatment. PETRA-MRA was shown to significantly reduce susceptibility artifacts induced by metallic devices, decrease the phase dispersion of labeled flow, and increase the signal intensity within the stent. Compared to TOF-MRA, PETRA-MRA has better consistency with DSA in image quality and stenosis measurement, especially for follow-up assessments after stent angioplasty.

4247		Deep Learning-Based Needle Tracking Trained on Bloch-Simulated Data and Evaluated on Clinical Real-Time bSSFP Images
		Ralf Vogel^1,2, Dieter Ritter², Jonathan Weine^2,3, Jonas Faust^2,4, Elodie Breton⁵, Julien Garnon^5,6, Afshin Gangi^5,6, Andreas Maier¹, and Florian Maier²
		¹Pattern Recognition Lab, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany, ²Siemens Healthcare, Erlangen, Germany, ³TU Dortmund, Dortmund, Germany, ⁴Universität Heidelberg, Heidelberg, Germany, ⁵ICube UMR7357, University of Strasbourg, CNRS, FMTS, Strasbourg, France, ⁶Imagerie Interventionnelle, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
		Recently, Deep Learning-based methods were used to track the position and orientation of needles in MR images in real-time. Synthetic training data can be generated in large amounts, without data privacy restrictions, and without the need of animal experiments. Therefore, we have simulated the image acquisition using virtual human phantoms containing randomly placed metallic needles in a Bloch simulator. The synthetic images were used to train a U-net to predict the position and orientation of the needle within the susceptibility artifacts of clinical images in less than $$$90\,\text{ms}$$$.

4248		Deep Learning-based MR-only Radiation Therapy Planning for Head&Neck and Pelvis
		Florian Wiesinger¹, Sandeep Kaushik¹, Mathias Engström², Mika Vogel¹, Graeme McKinnon³, Maelene Lohezic¹, Vanda Czipczer⁴, Bernadett Kolozsvári⁴, Borbála Deák-Karancsi⁴, Renáta Czabány⁴, Bence Gyalai⁴, Dorottya Hajnal⁴, Zsófia Karancsi⁴, Steven F. Petit⁵, Juan A. Hernandez Tamames⁵, Marta E. Capala⁵, Gerda M. Verduijn⁵, Jean-Paul Kleijnen⁵, Hazel Mccallum⁶, Ross Maxwell⁶, Jonathan J. Wyatt⁶, Rachel Pearson⁶, Katalin Hideghéty⁷, Emőke Borzasi⁷, Zsófia Együd⁷, Renáta Kószó⁷, Viktor Paczona⁷, Zoltán Végváry⁷, Suryanarayanan Kaushik³, Xinzeng Wang³, Cristina Cozzini¹, and László Ruskó⁴
		¹GE Healthcare, Munich, Germany, ²GE Healthcare, Stockholm, Sweden, ³GE Healthcare, Waukesha, WI, United States, ⁴GE Healthcare, Budapest, Hungary, ⁵Erasmus MC, Rotterdam, Netherlands, ⁶Newcastle University, Newcastle, United Kingdom, ⁷University of Szeged, Szeged, Hungary
		MR imaging offers unique advantages for Radiation Therapy Planning (RTP) via excellent soft-tissue contrast for the delineation of the tumor target volume and surrounding organs-at-risk (OARs). Remaining challenges include absent CT information (required for accurate dose calculation) and time-consuming manual tumor and OAR contouring. Here we describe the application of Deep Learning for MR-only RTP in terms of synthetic CT conversion and automated OAR delineation. Exemplary results are illustrated from an ongoing MR-only RTP study in head&neck and pelvis.

4249		Neural network based denoising of high temporal resolution cine images for tumor tracking in MR-guided radiotherapy
		Florian Friedrich^1,2, Juliane Hörner-Rieber³, Peter Bachert^1,2, Mark E. Ladd^1,2,4, and Benjamin R. Knowles¹
		¹Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Department of Physics and Astronomy, Heidelberg University, Heidelberg, Germany, ³Department of Radiation Oncology, University Hospital of Heidelberg, Heidelberg, Germany, ⁴Faculty of Medicine, Heidelberg University, Heidelberg, Germany
		MR-linac systems allow for real-time tumor position updates. Higher temporal resolution imaging through k-space undersampling allows for an increased number of position updates, however iterative reconstructions may negate the decrease in acquisition time and undersampling artifacts may impact tracking stability. In this study a fast method to denoise and suppress image artifact using a U-net is presented. Undersampled Cartesian and radial cine images were acquired from a patient with a liver tumor on an MR-linac. Tumor tracking stability was assessed. Denoising was found to improve tracking stability and has potential in high temporal resolution cine imaging on MR-linac systems.

4250		Towards higher accuracy mapping of MRI to electron density using a 3D deep CNN for MRI-only radiotherapy treatment planning
		Jessica E Scholey¹, Abhejit Rajagopal², Elena Grace Vasquez³, Atchar Sudhyadhom⁴, and Peder Eric Zufall Larson²
		¹Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA, United States, ²Department of Radiology, University of California, San Francisco, San Francisco, CA, United States, ³Department of Physics, University of California, Berkeley, Berkeley, CA, United States, ⁴Department of Radiation Oncology, Harvard Medical School, Boston, MA, United States
		We implemented a novel approach of using MRI to synthesize CT datasets acquired at MV photon energies for more accurate electron density mapping in radiotherapy treatment planning. We used a 3D deep convolutional neural network and demonstrated clinical proof-of-concept by evaluating the dosimetric impact of using synthetic datasets in a test radiotherapy treatment plan. The proposed method produced mean MAE of 72.8±17.3 HU and SSIM of 0.82 in the test dataset. The dose distributions computed on the test case produced 100% gamma passing rate (computed at 3%/3mm) indicating that synthetic MV images may be used for clinical treatment planning.

4251		Multi-Task MR Simulation for Abdominal Radiation Treatment Planning: Technical Development
		Junzhou Chen^1,2, Pei Han^1,2, Fei Han³, Zhehao Hu^1,2, Nan Wang^1,2, Wensha Yang⁴, Anthony G Christodoulou^1,2, Debiao Li^1,2, and Zhaoyang Fan^1,2,5
		¹Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, 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, ⁴Department of Radiation Oncology, University of Southern California, Los Angeles, CA, United States, ⁵Department of Radiology, University of Southern California, Los Angeles, CA, United States
		MRI can provide superior soft tissue contrasts for radiation therapy planning. However, radiation planning in the abdomen is especially difficult because respiratory motion can cause misregistration across separate scans with different contrast weightings due to inconsistent breath holds or poor patient compliance. While some studies have produced volumetric and motion-resolved images, they are all limited to a single contrast which is suboptimal for radiation planning. To address these issues, we present a free-breathing MR imaging platform that produces multi-contrast and motion-resolved volumetric images using MR-multitasking, dedicated for radiation therapy planning, and under a 9:30 mins scan time.

4252		Image quality comparisons of novel and commercial coil setups in MRI for head and neck radiotherapy simulation
		Evangelia Kaza¹, Jeffrey P Guenette², Christian V Guthier¹, Steven Hatch³, Alexander Marques³, Lisa Singer¹, and Jonathan D Schoenfeld¹
		¹Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, United States, ²Division of Neuroradiology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, United States, ³Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute, Boston, MA, United States
		Quality characteristics of healthy volunteer head images (SNR, CNR, artifact size) were compared between two flexible coil arrangements encompassing radiotherapy immobilization masks relative to a gold standard diagnostic Head/Neck20 coil that cannot accommodate the masks. The novel arrangement of two UltraFlexLarge18 coils provided higher SNR ratios and was more spacious than the commercially recommended arrangement of two FlexLarge4 coils. Artifact size and CNR ratios were similar for the two coil setups. Clinical application of the UltraFlexLarge18 coil arrangement would be advantageous for head and neck radiotherapy MRI simulations due to higher SNR and increased patient comfort.

4253		Real-Time B0 Correction in a MRI Guided Radiotherapy System
		Austen Curcuru¹, Deshan Yang^1,2, and Michael Gach^1,2,3
		¹Biomedical Engineering, Washinton University in Saint Louis, Saint Louis, MO, United States, ²Radiation Oncology, Washinton University in Saint Louis, Saint Louis, MO, United States, ³Radiology, Washinton University in Saint Louis, Saint Louis, MO, United States
		MRI linear accelerator hybrid systems use balanced steady state free precession sequences (bSSFP) during radiotherapy due to the sequence’s high signal to noise ratio and rapid acquisition times. However, bSSFP sequences are highly sensitive to off-resonance effects.¹ As a result, the position and velocity of the radiotherapy gantry can cause imaging artifacts that can impact tumor tracking and cause fluctuations in the main magnetic field that can result in radiotherapy/MRI isocenter misalignments. Sequence parameters were adjusted during the sequence run time to reduce these issues by integrating a navigator into the bSSFP sequence and measuring B₀ variations in real-time.

4254		Respiratory Motion Detection and Reconstruction Using CAPTURE and Deep Learning for a 0.35T MRI-LINAC System: An Initial Study
		Sihao Chen¹, Cihat Eldeniz¹, Weijie Gan¹, Ulugbek Kamilov¹, Deshan Yang¹, Michael Gach¹, and Hongyu An¹
		¹Washington University in St. Louis, Saint Louis, MO, United States
		Magnetic Resonance Imaging Guided Linear Accelerator (MRI-LINAC) combines an MRI system with a linear accelerator radiotherapy system to treat patients. The MRI-LINAC uses MR to track organ or lesion motion and gates the radiation beam accordingly. In this study, we demonstrate the combination of a T1-weighted self-navigated respiratory motion detection method (CAPTURE) with a deep learning 4D reconstruction (Phase2Phase, P2P) method to derive the 3D deformable respiratory motion field from data acquired on a 0.35 T ViewRay MRI-LINAC system. This initial study demonstrated promising results despite the low SNR at this field strength.

4255		Joint Radial Trajectory Correction for Fast T2* Mapping on an MR-Linac
		Wajiha Bano^1,2, Will Holmes^1,2, Mohammad Golbabaee³, Alison Tree^1,2, Uwe Oelfke^1,2, and Andreas Wetscherek^1,2
		¹Joint Department of Physics, The Institute of Cancer Research, London, United Kingdom, ²The Royal Marsden NHS Foundation Trust, London, United Kingdom, ³Computer Science Department, The University of Bath, Bath, United Kingdom
		Measuring T2* relaxation during the course of MR-guided radiotherapy can characterize tumour hypoxia, which is associated with treatment resistance. T2* mapping with radial trajectories allows for efficient coverage of k-space but is susceptible to errors arising from gradient delays. We propose a method that jointly estimates gradient delays and T2* using model-based reconstruction. Using the numerical phantom and the in-vivo prostate data we demonstrated that the proposed approach performs better for different noise levels for both fully sampled and undersampled datasets. This will allow better integration of T2* mapping for hypoxia imaging into an MR-linac treatment work flow.

4256		Diffusion changes in prostate cancer patients undergoing radiation treatment on an MR-Linac system: Preliminary findings
		Colleen Bailey^1,2, Rachel W Chan¹, Jay Detsky^3,4, Danny Vesprini^3,4, and Angus Z Lau^1,2
		¹Odette Cancer Centre, Sunnybrook Research Institute, Toronto, ON, Canada, ²Medical Biophysics, University of Toronto, Toronto, ON, Canada, ³Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, ⁴Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
		Eight prostate cancer patients undergoing radiation treatment were scanned on an MR-Linac with conventional ADC and high-b diffusion protocols at each of five treatment fractions. With the system’s weaker gradients and longer echo times, 6/8 patients had visible lesions at the maximum b-value of 2000 s/mm². Fits to the VERDICT model demonstrated higher intracellular fraction in the lesion, inversely correlated with ADC. In three patients, ADC increased starting at the third treatment time point; a fourth patient exhibited a transient ADC increase. Future work will correlate these changes with biochemical recurrence to test their relevance as a biomarker.

4257		MRI-based tumor localisation after tantalum clip placement for proton beam therapy planning of uveal melanoma
		Myriam Jaarsma-Coes^1,2, Teresa Ferreira¹, Marina Marinkovic², Khanh Vu², Gre Luyten², Coen Rasch³, Berit Verbist¹, and Jan-Willem Beenakker^1,2
		¹Radiology, Leiden University Medical Center, Leiden, Netherlands, ²Ophthalmology, Leiden University Medical Center, Leiden, Netherlands, ³Radiotherapy, Leiden University Medical Center, Leiden, Netherlands
		For proton beam therapy (PBRT) of Uveal Melanoma, tantalum clips are surgically sutured on the outside of the eye to mark the tumour edge. To aid in the 3D clip localisation and modelling of the tumor, a dedicated MRI protocol was developed and evaluated. In 51% of the clips, the MRI and per-operative measurements differed less than 1.0mm. In 28% of the clips the discrepancy between the MRI and peroperative measurement was attributed to the complex tumor geometry or anterior tumor localisation. For the majority of the patients MRI added valuable information to the peroperative measurements, improving PBRT planning.

4258		Deep learning based synthetic CT skull for transcranial MRgFUS interventions using 3D V-net–Transfer learning implications
		Pan Su^1,2, Sijia Guo^2,3, Steven Roys^2,3, Florian Maier⁴, Thomas Benkert⁴, Himanshu Bhat¹, Elias R. Melhem², Dheeraj Gandhi², Rao P. Gullapalli^2,3, and Jiachen Zhuo^2,3
		¹Siemens Medical Solutions USA, Inc., Malvern, PA, United States, ²Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland, School of Medicine, Baltimore, MD, United States, ³Center for Metabolic Imaging and Therapeutics (CMIT), University of Maryland Medical Center, Baltimore, MD, United States, ⁴Siemens Healthcare GmbH, Erlangen, Germany
		Transcranial MRI-guided focused ultrasound (tcMRgFUS) is a promising technique for treating multiple diseases. It is desirable to simplify the clinical workflow of tcMRgFUS treatment planning. Previously, feasibility of leveraging deep learning to generate synthetic CT skull from ultra-short echo time (UTE) MRI has been demonstrated for tcMRgFUS planning. In this study, 3D V-Net was used for skull estimation, by taking advantage of 3D volumetric images. Furthermore, feasibility of applying pre-trained model in new dataset was studied, demonstrating the possibility of generalization across various sequences/protocols and scanners.

4259		FMRI of Post High-Frequency Focused Ultrasound Ablation of ViM Shows Reduced Ipsilateral Thalamic and Cortical Motor Activation
		Anna Crawford¹, Mark Lowe¹, Sean Nagel², Daniel Lockwood¹, Emmanuel Obusez¹, Andre Machado², and Stephen Jones¹
		¹Imaging Institute, Cleveland Clinic Foundation, Cleveland, OH, United States, ²Neurological Institute, Cleveland Clinic Foundation, Cleveland, OH, United States
		High Intensity Focused Ultrasound (HIFU) in now entering clinical practice, for example to treat essential tremor (ET) by creating small lesions in the thalamus. Due to small size of treatment lesions, treatment success depends critically on targeting, which is classically done using measurements and landmarks. We explore an alternative method using functional imaging to guide targeting and assess efficacy, specifically using 7T task-related fMRI. We present preliminary data of the patterns of BOLD activation in a set of patients before and after HIFU.

4260		Comparison of Automated Thalamic Segmentation Techniques: Applications in MRgFUS Planning
		Kain Kyle¹, Jerome Maller², Yael Barnett³, Stephen Tisch³, Benjamin Jonker³, Michael Barnett¹, Arkiev D'Souza¹, and Chenyu Wang¹
		¹University of Sydney, Sydney, Australia, ²GE Healthcare, Sydney, Australia, ³St Vincent's Hospital Sydney, Sydney, Australia
		Investigation of thalamic segmentation tools FreeSurfer and THOMAS for use in MRgFUS planning.

4261		Reduced-FOV 3D MR-ARFI with a joint reconstruction for localizing the focused ultrasound beam in neuromodulation
		Huiwen Luo^1,2, Michelle K. Sigona^1,2, Li Min Chen^2,3, Charles F. Caskey^2,3, and William A. Grissom^1,2,3
		¹Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ³Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States
		Magnetic resonance acoustic radiation force imaging (MR-ARFI) can be used to localize the focal spot in MR-guided focused ultrasound (FUS) by encoding the ultrasound-induced displacements into the phase of an MR image. A two-minute reduced-FOV 3D MR-ARFI scan with a joint image reconstruction method at 3 Tesla is proposed to image and localize the entire focus in FUS neuromodulation with a low FUS duty-cycle of 0.85%. In this work the reduced FOV MR-ARFI pulse sequence is demonstrated and the proposed k-space undersampling with joint sparse difference image reconstruction to achieve a two-minute scan time is validated.

Multimodal Imaging & Auxiliary Devices

Interventional, Multimodal & Auxiliary Engineering

Engineering/Interventional/Safety

4262		A compact and clonable ultrasound-based sensor system to monitor physiological motion
		Bruno Madore¹, Cheng-Chieh Cheng², and Frank Preiswerk³
		¹Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States, ²Computer Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan, ³Amazon Robotics, Westborough, MA, United States
		Physiological motion continues to be a problem in MRI and PET, as it can cause blurring and other types of artifacts. We developed a compact, clonable ultrasound-based sensor system that monitors internal motion directly. Alternative means of motion monitoring often involve hardware (including the scanner itself) that is attached to floors, walls and/or ceilings and thus cannot follow the patient from one room to another, from one procedure to the next. The present sensors attach to the skin, they can follow the patient, and as such they may help link different procedures in ways that take internal motion into account.

4263		Acoustically transparent and low-profile head coil for high precision magnetic resonance guided focused ultrasound at 3 T
		Isabelle Saniour¹, Fraser Robb², Victor Taracila², Jana Vincent², Henning U. Voss¹, Michael G. Kaplitt³, J. Levi Chazen¹, and Simone Angela Winkler¹
		¹Weill Cornell Medicine, New York, NY, United States, ²MR Engineering, GE Healthcare, Aurora, OH, United States, ³Department of Neurological Surgery, Weill Cornell Medicine, New York, NY, United States
		Magnetic resonance guided focused ultrasound (MRgFUS) is a non-invasive therapeutic modality for neurodegenerative diseases that allows real-time imaging of the targeted regions. However, MR image quality is poor and severely limits the technology due to the use of the body coil for focal targeting. Acoustic simulations demonstrated an acoustic transparency (signal loss <1%) of the coil when used for thalamic sonication. In vivo results showed increase of the SNR over the body coil by a factor of 7.3 and 7.6 in a brain image with and without the presence of the transducer, respectively.

4264		A dedicated 3-ch breast coil for Microwave Tomography at 3T
		Xiaoyu Yang¹, Thomas Eastlake¹, Tsinghua Zheng¹, Shireen Geimer², Timothy Raynolds², Paul Meaney², and Keith Paulsen²
		¹Innovation, Quality Electrodynamics, LLC, Mayfield Village, OH, United States, ²Thayer School of Engineering, Dartmouth College, Hanover, NH, United States
		MR breast imaging has high sensitivity but not high specificity. Microwave Tomography (MT) provides complimentary permittivity information that may improve specificity. MT has poor spatial resolution. Combining MR and MT may address both spatial and specificity issues. Previous MT and MR work demonstrated the MT-MR combination potential. However, there is no dedicated MR coil available for MT-MR combination. The only available coils are the whole-body coil or a single-loop coil that have poor MR image quality. A dedicated 3-ch MRI coil is proposed here for superior MRI imaging quality which enables the next step MT-MR volunteer evaluation.

4265		A Dedicated Multichannel Head Coil Array for PET Insert on 3 T MRI
		Jo Lee^1,2, Ziru Sang^1,2, Yongfeng Yang^1,2, Xiaoliang Zhang³, and Ye Li^1,2
		¹Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, ²Shenzhen Key Laboratory for MRI, Shenzhen, China, ³Department of Biomedical Engineering, State University of New York, Buffalo, NY, United States
		Simultaneous positron emission tomography/ magnetic resonance imaging(PET/MR) provides advantages in clinical and research applications of human’s brain. The two systems, MRI and PET, can work complementary to provide more information for medical diagnosis. As most research and clinical institutes already have MRI systems, an insert PET and matched MRI coil would be a more economical choice than a PET/MR system. In this study, we designed and built a dedicated quadrature birdcage/47Rx head coil array for PET insert on human’s brain study. The flip-angle maps and SNR performances were measured through a dedicated phantom. Anatomical images were scanned on a volunteer.

4266		Vector Modulator Based Automated Active Compensation of Direct Feedthrough in Magnetic Particle Imaging
		Bilal Tasdelen^1,2, Mustafa Utkur^1,2, Ergin Atalar^1,2, and Emine Ulku Saritas^1,2
		¹Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, ²National Magnetic Resonance Research Center (UMRAM), Ankara, Turkey
		In magnetic particle imaging (MPI), simultaneous excitation and signal acquisition leads to direct feedthrough interference. While this interference can be mitigated up to some extent with passive compensation, its time-varying nature necessitates active compensation methods to achieve the sensitivity levels needed for applications such as stem cell tracking. We have recently proposed an active compensation technique for MRI, which uses a vector modulator and a lookup-table-based algorithm for reducing the direct feedthrough in the analog domain. Here, we adapt this technique to MPI, demonstrating a successful recovery of the fundamental frequency and a significant increase in detection sensitivity.

4267		Interventional Magnetic Particle Imaging Open-bore Scanner Design
		Michael Seeg¹, Martin Rueckert¹, Stefan Herz², Thomas Kampf^1,3, Thorsten Bley², Volker Behr¹, and Patrick Vogel¹
		¹Experimental Physics V, Julius-Maximilians-University, Wuerzburg, Germany, ²Department of Diagnostic and Interventional Radiology, University Hospital, Wuerzburg, Germany, ³Department of Diagnostic and Interventional Neuroradiology, University Hospital, Wuerzburg, Germany
		X-ray-guided endovascular interventions are important treatment approaches for many cardiovascular diseases such as myocardial infarction, stroke or occlusive peripheral arterial disease. However, they pose the risk of radiation exposure to patients and staff. Magnetic particle imaging may provide a radiation-free alternative for diagnostic and image guided treatment. A new open bore scanner concept, based on a traveling field free line and super paramagnetic iron oxide tracers is developed especially for interventional treatments. Due to the open design the scanner provides good accessibility to the patient.

4268		MR safe electromagnetic direct current motor
		Lorne W Hofstetter¹, J Rock Hadley¹, Robb Merrill¹, and Dennis L Parker¹
		¹Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, United States
		Combining the unparalleled soft-tissue imaging capabilities of MR imaging with the precision of robotic-assisted surgeries has the potential to revolutionize image-guided surgical interventions. However, strong magnetic fields generated by the MR system prevent the use of conventional robotic servo motor technologies. Here we present a direct current electromagnetic motor design that uses the electromagnetic interaction between the MR B0 field and currents in the rotor windings to generate rotational mechanical actuation. The motor stall torque and interactions caused by simultaneous motor operation and MR imaging are characterized. This new motor may be useful for robotic assisted interventions performed under MR-guidance.

4269		Real-time electric field estimation in transcranial magnetic stimulation using deep learning and magnetic resonance imaging
		Guoping Xu^1,2, Yogesh Rathi^2,3, Joan A Camprodon^3,4, and Lipeng Ning^2,3
		¹Wuhan Institute of Technology, Wuhan, China, ²Brigham and Women's Hospital, Boston, MA, United States, ³Harvard Medical School, Boston, MA, United States, ⁴Massachusetts General Hospital, Boston, MA, United States
		Transcranial magnetic stimulation (TMS) is an effective treatment approach for mental disorders. Accurate and rapid prediction of TMS-evoked electric field (E-field) in brain tissue is important for accurate targeting and to understand the mechanism of treatment response. The standard method for E-field prediction is based on physical modeling which usually takes long computational time. In this work, we introduce a method based on deep neural networks (DNNs) for real-time E-field prediction. We show that the trained DNN can predict high-precision whole-brain E-field in 0.24 seconds. Moreover, diffusion-MRI based tissue conductivity tensor can improve the prediction accuracy of E-field.

4270		A wearable “RF-EEG Cap” for full head coverage concurrent TMS/EEG/fMRI experiments at 3T: a feasibility study
		Lucia Navarro de Lara^1,2, Padmavathi Sundaram ^1,2, Lena Nohava³, Elmar Laistler³, Mohammad Daneshzand^1,2, Lawrence Wald^1,2, Jason Stockmann^1,2, and Aapo Nummenmaa^1,2
		¹Martinos Center - MGH, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
		To enable concurrent non-invasive stimulation (TMS) and whole-head multimodal imaging (EEG-fMRI), we propose to apply flexible RF coil technology to build a first-of-its-kind TMS compatible integrated multimodal imaging array, the “RF-EEG cap”. The proposed system allows unrestricted positioning of the TMS coil across the entire scalp. We built a 2-channel prototype and conducted a feasibility study analyzing the effects of a TMS coil and EEG-electrodes on the imaging quality (SNR/B0 maps), the in-bore EEG data quality and EPI timeseries stability. Our results indicate that the flexible coaxial RF technology is a feasible choice to build the proposed “RF-EEG Cap”.

4271		Quantification of HD-EEG net attenuation on 18F-FDG static PET: a phantom and human brain study
		Erica Silvestri^1,2,3, Marco Castellaro^1,4, Alessandra Zorz⁵, Andrea Bettinelli ^1,5, Cristina Campi⁶, Marta Paiusco⁵, Diego Cecchin^2,7, and Alessandra Bertoldo^1,2
		¹Department of Information Engineering, University of Padova, Padova, Italy, ²Padova Neuroscience Center, University of Padova, Padova, Italy, ³Department of Neuroscience, University of Padova, Padova, Italy, ⁴Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy, ⁵Department of Medical Physics, Veneto Institute of Oncology IOV - IRCCS, Padova, Italy, ⁶Department of Math, University of Padova, Padova, Italy, ⁷Department of Medicine, Unit of Nuclear Medicine, University of Padova, Padova, Italy
		Simultaneous trimodal EEG-PET-MR imaging can be a tool to delve deeper in the healthy human brain functioning. One of the aspects scarcely investigated is the interplay between HD-EEG net and PET signal detection and reconstruction. In this work, we assess the impact of HD-EEG on both attenuation corrected (AC) and non-attenuation corrected (NAC) PET images. We found that HD-EEG net attenuates PET signal in NAC images in both phantom and human brain, respectively of 3.01%(±3.69%) and of 0.53%(±5.89%). AC images show an opposite behaviour: attenuation correction factor tends to be overestimated in CT- and UTE-derived UMAP obtained with HD-EEG net.

4272		Triggering pulse generation by non-contact monitoring of heart rate using an antenna with 600 MHz resonance
		Kazuya Okamoto¹, Takafumi Ohishi², Sojuro Kato¹, Ryuichi Nanaumi³, Kenji Oyama³, and Kazuhiko Fukutani³
		¹Advanced MRI Development PJ Team, Canon Medical Systems Corp., Kawasaki, Japan, ²Advanced Technology Research Department, Research and Development Center, Canon Medical Systems Corp., Kawasaki, Japan, ³Medical Products Technology Development Center, R&D Headquarters, Canon Inc., Tokyo, Japan
		New non-contact cardiac and respiratory gating method have been developed, which includes an antenna monitoring heart and respiration movement, and independent triggering pulse generation unit with signal processing software. The resonance frequency of the dipole antenna was tuned to around 550MHz on the chest. The triggering pulse generation unit detected and digitized the S11 signals from the antenna. IIR filter removed the low frequency component and a template matching technique was used to seek the triggering points at the inflection point of filtered waveform. As a result, the prospective gating cardiac imaging was successfully performed for volunteers.

4273		MRI data transmission via fifth-generation (5G) cellular networks
		Nicolai Spicher¹, Ramon Barakat¹, and Thomas Martin Deserno¹
		¹Peter L. Reichertz Institute for Medical Informatics, TU Braunschweig and Hannover Medical School, Braunschweig, Germany
		In the last years, research in MRI has expanded towards portable technology, e.g., trailer units carrying conventional scanners or bedside scanners with low-field strengh. The increased portability and shift away from the centralized hospital environment requires wireless data transmission with appropriate data rates to unfold its full potential. In this work, we made use of current fifth-generation (5G) cellular networks for transmitting DICOM data. We demonstrate the potential of reaching more than 50 Mbit/s upload speed using consumer-grade hard- and software. This holds great potential for cellular transmission of data from portable scanners, allowing to increase access to MRI technology.

4274		Test Bed for High Speed Serial Wireless MRI Data Studies
		Audrey Chan¹, Fraser Robb², John Pauly³, Shreyas Vasanawala⁴, and Greig Cameron Scott⁵
		¹Victoria University of Wellington, Wellington, New Zealand, ²GE Healthcare, Aurora, OH, United States, ³Stanford University, Stanford, CA, United States, ⁴Radiology, Stanford University, Stanford, CA, United States, ⁵Electrical Engineering, Stanford University, Stanford, CA, United States
		We developed a test system to perform pseudo-random binary sequence (PRBS) generation and clock/data recovery to assess high speed serial link performance of wireless and optical signal integrity for MRI data interfacing. We demonstrate applications using up to 1Gbps signal rates and show impairments for wireless amplitude shift keyed data transmission, as well as plastic fiber optical interfacing.

4275		Wireless Powered Frequency Encoding of Locally Detected MR Images for Remote Signal Transmission
		Wei Qian¹ and Chunqi Qian¹
		¹Michigan State University, East Lansing, MI, United States
		With a compact and batteryless design, the wireless powered parametric oscillator can simultaneously down-convert and frequency encode locally detected MR signals, and wirelessly transmit them to remotely coupled external receivers, thus maintaining superior sensitivity of localized detectors over larger distance separations.

4276		Single board computer as a satellite-linked, deep learning capable pocket MR workstation: a feasibility study
		Keerthi Sravan Ravi^1,2, John Thomas Vaughan Jr.², and Sairam Geethanath²
		¹Biomedical Engineering, Columbia University, New York, NY, United States, ²Columbia Magnetic Resonance Research Center, New York, NY, United States
		This work shows the feasibility of employing a Raspberry Pi (RPi) single-board computer as a deep learning capable MR workstation. RPi’s ability to run a Tensorflow-Lite optimized brain tumour segmentation model is demonstrated. A comparison of data upload across fixed broadband, cellular broadband (LTE, 3G) and satellite terminal methods of internet access is presented. Finally, the setup described in this work is compared with a conventional fixed MRI workstation and a portable MRI workstation.

4277		STAR MRI With Non-Magnetic, Integrated Circulator based on Switched Transmission Lines
		Aravind Nagulu¹, Ahmed Kord¹, Gehua Tong¹, Michael Garwood², Lance DelaBarre², Djaudat Idiyatullin², SungMin Sohn³, J. Thomas Vaughan¹, and Harish Krishnaswamy¹
		¹Columbia University, New York, NY, United States, ²University of Minnesota, Minneapolis, MN, United States, ³Arizona State Univeristy, Tempe, AZ, United States
		Traditional MRI employs time division duplexing between the receiver (RX) and transmitter (TX) to avoid RX saturation from TX self-interference. Large switching time between the TX and RX modes demands large TX power and constricts the imaging to tissues with large relaxation times. In this work, we propose a magnetic-free, switch-transmission line circulator which is fully compatible with MRI systems and achieve simultaneous transmit and receive (STAR) MRI.

4278		A 5.7mW 1.5T Silicon Germanium Pre-Amp, and its Effects on Image Distortion
		Christopher Vassos¹, Fraser Robb², Shreyas Vasanawala³, John Pauly¹, and Greig Scott¹
		¹Electrical Engineering, Stanford University, Stanford, CA, United States, ²GE Healthcare, Aurora, OH, United States, ³Radiology, Stanford University, Stanford, CA, United States
		A 5.7mW Silicon Germanium Pre-Amplifier was constructed, characterized, and its potential impact on image quality demonstrated. The amplifier demonstrates significant power savings relative to current implementations at the cost of increased device non-linearity and decreased input impedance. A benchtop measurement setup was constructed to simulate coils signals in conjunction with a physical receive chain. Measured image distortion began at peak input powers of -25dBm. This corresponds to high bandwidth, high dynamic range imaging sequences. For small coil sizes this distortion may not play a role, reducing the power barrier to wireless receive arrays.

4279		Hybrid Pair Ratio Adjustable Power Splitter using off-shelf components and easy-to-replace microstrip phase shifter
		Yue Zhu^1,2, William A Grissom^1,2,3,4, John C Gore^1,2,3,4, and Xinqiang Yan^1,2
		¹Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, ³Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ⁴Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, United States
		A low loss ratio adjustable power splitter (RAPS) was designed with a Wilkinson Splitter, a pair of transmission lines, and a hybrid coupler. There are some potential issues with the previous RAPS: 1. Build a high-performance RAPS circuit with lumped elements is challenging and laborious at 298 MHz. 2. The 100-Ohm RF decoupling resistor poses a safety hazard to the patient. In this abstract, the Wilkinson splitter was replaced with a hybrid coupler, and the adjustable transmission lines are replaced with printed microstrip lines to mitigate the problems mentioned above.

4280		High Speed Serial ASK Signal Integrity for Wireless MRI
		Greig Cameron Scott¹, Audrey Chan², Wonje Lee³, Fraser Robb⁴, John Pauly⁵, and Shreyas Vasanawala⁶
		¹Electrical Engineering, Stanford University, Stanford, CA, United States, ²Victoria University of Wellington, Wellington, New Zealand, ³Pediatric Radiology, Stanford University, Stanford, CA, United States, ⁴GE Healthcare, Aurora, OH, United States, ⁵Stanford University, Stanford, CA, United States, ⁶Radiology, Stanford University, Stanford, CA, United States
		A major challenge of wireless MRI is how to implement the data link. Here, progress is made using amplitude shift keyed diode ring modulators, serializer/deserializer components and clock/data recovery to demonstrate bit rate transmissions up to 600 Mbps. High gain biquad reflector antennas and UWB antennas are compared for carriers between 3 and 5 GHz. These prototypes also demonstrate bandwidth limitations and electrodynamic interactions in a birdcage test bore on wireless signal integrity. Even if dedicated wireless ICs are not possible, we believe components exist to make an easily integrated modulator for MRI wireless data transmission.

4281		A Sip in the Bore: How to Make Coffee with an MRI System
		Michael Bock¹, Thomas Lottner¹, and Ali Caglar Özen^1,2
		¹Radiology - Medical Physics, University Medical Center, Medical Faculty, University Freiburg, Freiburg, Germany, ²German Consortium for Translational Cancer Research (DKTK), Freiburg, Germany
		Energy harvesting of the RF fields has been proposed to power small milliwatt RF amplifiers. In this work we demonstrate that the time-varying gradient fields can deliver much higher power levels up to a kW which we used to energize a conventional drip coffee machine. A large pick-up coil was designed in which voltages of 100-200V were induced by rapidly oscillating gradients. The coil was connected to a commercial coffee machine in the magnet, and coffee was prepared in and with the MRI in just 5min.