08:15 | 0463.
| 7 Tesla 31P Birdcage / 16-channel 1H Loop and Dipole Array integrated with Parallel Transmit System Bei Zhang1, Tom Geraedts2, Wim Prins2, Conrad Gohl2, Bart-Jan van den Berg2, Paul Sanders2, Ivan Dimitrov2, Geert-Jan Plattel2, Daniel Lowrance1, Peter van der Meulen2, and Anke Henning1 1Advanced Imaging Research Center, UTSouthwestern Medical Center, Dallas, TX, United States, 2Philips Healthcare, Best, Netherlands Keywords: RF Arrays & Systems, Parallel Transmit & Multiband, 31P/1H imaging, Dual-tuned array design, ultra-high field, parallel transmit system Motivation: Integrating multinuclear applications into parallel transmit system (PTx) at ultra-high field MRI systems will provide uniform transmit field and good SNR for both proton and the x-nuclei. Goal(s): Design, build and integrate a 7T 31P/1H head array into a 7T PTx system that supports multinuclear applications. Approach: Use 8 loops and 8 folded dipoles as 1H transceivers, and a birdcage as 31P transceiver, for 31P/1H MRS and MRI in a 7T PTx system Results: Phantom and in vivo experimental results show that the coil can provide homogeneous and good SNR signals for both 31P and 1H in ROI Impact: Elevating multinuclear studies with 7T parallel transmit system,
providing uniform transmit fields and good receive sensitivity profile for both
proton and x-nuclei in ROI. A potential game-changer for metabolic studies in
body applications at ultra-high fields, advancing medical research. |
08:15 | 0464.
| Using Inductively-Coupled Dipole Pairs as Array Elements for Improving Whole-Brain Coverage at 9.4T Kristina Popova1, Stanislav Glybovski1, Klaus Scheffler2, Nikolai Avdievich2, and Georgiy Solomakha2 1School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation, 2High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany Keywords: RF Arrays & Systems, Brain, Array, UHF, dipole, coverage Motivation: At ultra-high fields, homogeneity of brain MRI is deteriorated by the subject-specific non-uniform distribution of RF magnetic field B1+. Goal(s): To design a 9.4T eight-channel transceiver dipole array with improved homogeneity of B1+ in the axial direction with better whole-brain coverage. Approach: We used an array consisting of paired passively coupled folded-end dipoles. We numerically optimized the B1+ homogeneity by adjusting the overlap between the folded ends of the active and passive dipoles and the load impedance of the passive one. Results: The proposed array demonstrated improved B1+ whole-brain homogeneity including the upper C-spine compared to several state-of-the-art dipole and loop arrays. Impact: The presented antenna element of coupled folded dipoles can be
used in designing UHF array coils with improved longitudinal whole-brain
coverage. Such coils can be beneficial for studies where imaging of the entire brain
including the upper C-spine is required. |
08:15 | 0465.
| Eight-channel dual-tuned coaxial‐transmission‐line coils array for human head imaging at 10.5 Tesla Komlan Payne1, Yunkun Zhao1, Aditya Ashok Bhosale1, and Xiaoliang Zhang1 1Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States Keywords: Parallel Transmit & Multiband, Hybrid & Novel Systems Technology, Dual-tuned, Hybrid & Novel Systems Technology, RF Array, Parallel Imaging Motivation: The capability of coaxial-transmission-line (CTL) RF coils to exhibit multimode operating frequencies make them versatile for applications involving dual-nuclear coil resonators for Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy studies. Goal(s): Design eight-channel dual-tuned CTL coils array for human head imaging at 10.5 Tesla and address the electromagnetic coupling issue between elements of the array. Approach: The high impedance feature of the high-frequency mode helps to achieve sufficient decoupling for 1H channels while the magnetic wall technique is used to decouple the low-frequency mode tuned to heteronuclear frequency. Results: A well-decoupled array of dual-tuned CTL coils is feasible for head imaging at 10.5T. Impact: The feasibility of advanced multichannel dual-tuned RF coil array can contribute to more informative imaging and spectroscopy, which is valuable in various medical and research applications. |
08:15 | 0466.
| Local SAR and Uncertainty Estimation for Brain Imaging by Bayesian Deep Learning E.F. Meliado1,2,3, S. Mandija2,4, C.A.T. van den Berg2,4, and A.J.E. Raaijmakers1,2,5 1Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2Computational Imaging Group for MR diagnostics & therapy, Center for Image Sciences, University Medical Center Utrecht, Utrecht, Netherlands, 3Tesla Dynamic Coils BV, Zaltbommel, Netherlands, 4Department of Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands, 5Biomedical Image Analysis, Dept. Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands Keywords: Safety, Safety, specific absorption rate; local SAR; deep learning; Bayesian deep learning; uncertainty estimation Motivation: Local SAR cannot be measured during an MRI examination. Deep learning approaches are proving to be a solution for on-line subject-specific SAR assessment. Goal(s): The brain is the region of greatest clinical interest for ultra-high field MRI. Therefore, we apply for brain imaging a deep learning approach presented for local SAR assessment for body imaging. Approach: The Bayesian deep-learning approach maps the relation between subject-specific complex B1+-maps and the corresponding local SAR distribution, and predicts the spatial distribution of uncertainty at the same time Results: The Bayesian deep-learning approach for local SAR assessment in brain outperforms the previous application for prostate imaging. Impact: The application of Bayesian deep-learning
can allow the reduction of overly conservative RF safety constraints that limit
the performance of UHF-MRI. Furthermore, the joint estimation of uncertainty
can help the acceptance of such methods in clinical contexts. |
08:15 | 0467.
| Assessment of the Inter-Subject Variability of Peak Local Specific Absorption Rate for a Head Coil at 10.5T Mert Ates1,2, Tobey Haluptzok1, Gregor Adriany1, Gregory J Metzger1, Kamil Ugurbil1, Yigitcan Eryaman1, and Alireza Sadeghi-Tarakameh1 1Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, MN, United States, 2Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey Keywords: Safety, Safety Motivation: The safety factor, which scales SAR matrices used in real-time SAR monitoring, is commonly dominated by inter-subject variability. However, the contributions from various sources to that variability have not been fully evaluated. Goal(s): Assess the impact of different human model variations and different patient positions inside the coil, on the predicted peak local SAR for 10.5T head applications. Approach: The SAR inter-subject variability was investigated via EM simulations of two human models along with a wide variety of head positions inside an 8-channel coil at 10.5T. Results: The variability between head models was significantly more consequential than variations in a head model’s position. Impact: Simulating
realistic scenarios with wide appropriate variables, to calculate SAR with a
more accurate inter-subject variability on peak local SAR, has the potential to
improve patient safety without compromising the scanning quality at ultrahigh
field MRI. |
08:15 | 0468.
| Estimating Variations in SAR Calculations due to Within-Scan Patient Motion Using cGANs for Parallel RF Transmission at Ultrahigh Field MRI Katherine Anna Blanter1, Alix Plumley1, Shaihan Malik2, and Emre Kopanoglu1 1Cardiff University Brain Research Imaging Centre, Cardiff University, Cardiff, United Kingdom, 2Life Sciences & Medicine, Biomedical Engineering & Imaging Sciences, Department of Biomedical Engineering, King's College London, London, United Kingdom Keywords: Safety, Safety, UHF-MRI, SAR, pTx design Motivation: Specific absorption rate (SAR), a proxy measure for tissue heating, is affected by patient motion. SAR safety factors during MRI scanning are intentionally overconservative. Goal(s): While designed to ensure patient safety, overconservativeness impedes the utility of scanning with parallel-transmit (pTx) 7T MRI. We aim to relieve pTx MRI from overconservativeness while maintaining patient safety. Approach: We used deep learning to predict the location of hot-spots during head motion and applied them to a pTx design method which considers patient motion. Results: We report that hot-spots are overcalculated almost 1.5-fold when the degree of motion is not included compared to when it is. Impact: Deep learning-estimated local specific absorption rate (SAR) variations caused by patient motion may be combined with within-scan motion tracking and subject-specific SAR models to create personalized SAR supervision for patients who cannot remain still for high-performance scanning while ensuring patient-safety. |
08:15 | 0469.
| Towards dense parallel-transmit coil head array: 20-channel dipole and self-decoupled overlapped loop coil array design Melissa Ashley Ng Tseung1, Seng Foong Voon1, Menglu Wu1, and Özlem Ipek1 1School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom Keywords: RF Arrays & Systems, RF Arrays & Systems Motivation: Traditional dense transmit arrays for 7T imaging face decoupling challenges. A novel approach using self-decoupled coils can potentially overcome these limitations and enhance transmit efficiency. Goal(s): Evaluating an in-house developed 20-element array combining dipoles with self-decoupled overlapped loop coils. Approach: Bench measurements, electromagnetic simulations on phantom and Duke, and MRI acquisitions were conducted to investigate the coil array's performance, assessing individual channel B1+-map efficiencies and decoupling capacities Results: Decoupled individual B1+ maps for dipoles, self-decoupled and overlapped loops were obtained for 20-channel head array using MRI measurement and simulations on phantom at 7T. S-matrix results on bench and simulations showed decoupled coil elements. Impact: Searching for alternative and complex coil array design for transmit and receive arrays might enable for more efficient and fast imaging at MRI with high resolution to enable better diagnostics and improved treatment planning. |
08:15 | 0470.
| Tissue detail of pregnant body models needed to estimate SAR for fetal MRI Filiz Yetisir1,2, Esra Abaci Turk1,2, Elfar Adalsteinsson3, and P. Ellen Grant1,2 1Fetal-Neonatal Neuroimaging Developmental Science Center, Boston Children's Hospital, Boston, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Massachusetts Institute of Technology, Cambridge, MA, United States Keywords: Safety, Fetus, Electromagnetic simulations Motivation: Due to the large variation of the body shape and size in the pregnant population, several pregnant body models are needed in fetal MRI safety studies. However, creating detailed pregnant body models is challenging. Goal(s): Our goal is to investigate the effect of reducing maternal tissue detail on maternal and fetal SAR. Approach: We simplified >18 maternal tissues into 3 (muscle, lung and fat) in 7 pregnant body models and quantified the change in maternal and fetal SAR. Results: The value and location of maternal and fetal SAR changes by up to 13% and 34 mm with maternal tissue detail reduction. Impact: Simplification of maternal tissues into muscle, lung and fat changes maternal and fetal SAR (<14%) significantly less than the variation of SAR between pregnant subjects (>x2) and might provide a good trade-off between accuracy and practicality in RF safety studies. |
08:15 | 0471.
| Rapid Specific Absorption Rate Estimation of High-Field MRI via 3D U-net Architectures for MRI Safety Xi Wang1, Xiaofan Jia1, Shao Ying Huang2, and Abdulkadir C. Yucel1 1School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, Singapore, 2Engineering Product and Development, Singapore University of Technology and Design, Singapore, Singapore Keywords: Safety, Safety Motivation: Advancements in MRI technology towards high fields demand rapid and accurate SAR estimation tools for enhancing MRI safety, currently hindered by the computational cost of conventional physics-based simulators. Goal(s): The goal is to develop an efficient machine learning framework capable of estimating subject-specific SAR values rapidly. Approach: The study employs 3D U-net deep learning models with their variants to achieve rapid and accurate SAR estimations. Results: The proposed neural network model provides SAR estimations within 183ms, achieving approximately 10,000x acceleration over traditional physics-based simulators, with a mean relative error of 7.6%. Impact: The near real-time accurate SAR estimation achieved by proposed machine learning framework will allow (i) checking patient-specific
SAR while patient is lying in the MRI machine and (ii) performing ultra-fast
optimization and uncertainty quantification studies while designing new
high-field coils. |
08:15 | 0472.
| A high permittivity and conformable gel pad fabricated by the PVA freeze-thaw method for dielectric shimming in ultra-high-field MRI Mengyu Li1, Keyi Tang1, Shufeng Zhou1, Zhentao Zuo2, Huabin Zhu3, Shanshan Shan1, and Chunyi Liu1 1State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China, Soochow University, suzhou, China, 2State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, 3Suzhou Medcoil Healthcare Co., Ltd., suzhou, China Keywords: Shims, Shims, high-permittivity, sfaty, hydrogel pad Motivation: Utilize new material to fabricate high-permittivity pads for addressing the B1 inhomogeneity and safety issues in ultra-high-field MRI scanning. Goal(s): We aim to develop a new high permittivity pad with flexibility which can fit various body shapes. Different sizes and mass proportions of barium titanate powder were explored to achieve optimized mechanical properties and desired permittivity value. Approach: The gel pad is fabricated using the PVA freeze-thaw method, resulting in a stable gel structure that incorporates barium titanate powder, thereby possessing excellent mechanical properties and high permittivity. Results: Experimental results demonstrate of the gel pad's potential for clinical applications in ultra-high-field MRI scanning. Impact: This
abstract introduces a novel gel pad with high permittivity that can be
conformed to different shapes of scanned objects. It highlights the potential
of the gel pad in addressing safety issues in ultra-high-field MRI scanning. |
08:15 | 0473.
| Impact of RF imperfections on MRF-based and reference B1+ mapping methods with a commercial 1Tx/32Rx head coil Max Lutz1, Berk Silemek1, Frank Seifert1, Christoph Stefan Aigner1, Stephan Orzada2, Lance DelaBarre3, Tobias Schaeffter1,4,5, and Sebastian Schmitter1,2,3 1Physikalisch-Technische Bundesanstalt, Braunschweig and Berlin, Germany, 2Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 3Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 4Einstein Center Digital Future, Berlin, Germany, 5Department of Biomedical Engineering, Technical University of Berlin, Berlin, Germany Keywords: System Imperfections, System Imperfections: Measurement & Correction Motivation: Magnetic Resonance Fingerprinting (MRF) and preparation-based reference B1+ mapping approaches yielded an unexpected B1+ offset. Goal(s): Identify the origin of the B1+ offset. Approach: Pick-up coil measurements to evaluate the actual RF pulse shape using a commercial 1Tx/32Rx head-coil at 7T. Results: For the preparation-based B1+ mapping method with rectangular pulses, longer RF rise times (~100 µs) and phase variations (~10°) were observed. Furthermore, during the 21s-long MRF acquisition using sinc-pulses, an increased RF amplitude (~2.5%) was observed. By incorporating the measured RF alterations, the B1+ offset could be substantially reduced. Impact: Unidentified effects of the RF transmission such as deviation in envelope
and temporal instability affect measurements. Characterizing the RF
transmission enables quantification and correction of these deviations. |
08:15 | 0474.
| Comparison of Renal ASL Signal-to-noise Ratio and Corticomedullary Contrast between 3T and 5T MRI Xiangwei Kong1, Yanbin Li2, Mingyan Wu2, Xinzhen Zhang3, Chen Chen4, Xinyue Jiang1, and Jeff Lei Zhang1 1School of Biomedical Engineering, ShanghaiTech University, Shanghai, China, 2Central Research Institute, UIH Group, Shanghai, China, 3United Imaging Healthcare, Shanghai, China, 4Application Feature Solution, UIH Group, Shanghai, China Keywords: High-Field MRI, Arterial spin labelling Motivation: As the most promising method for measuring tissue perfusion, ASL suffers from low signal-to-noise ratio (SNR), with tagged blood typically causing only few percent of signal difference. Goal(s): Explore if the use of 5T MRI could lead to higher SNR and CNR for renal ASL than 3T. Approach: We performed FAIR-EPI on the kidneys of three healthy subjects at 6 inversion times on both 3T and 5T systems. SNR and CNR of difference images were calculated and compared. Results: SNR at 5T was 10.72±2.81, higher than 7.75±2.65 (P = 0.008) at 3T, and CNR were 9.08±4.08 and 6.53±2.14 (P=0.029), respectively. Impact: 5T
ASL provides difference images with higher SNR and CNR to allow faster
acquisition and better corticomedullary differentiation while
maintaining comparable image quality. |
08:15 | 0475.
| A 48-channel multi-coil shim array for B0 inhomogeneities correction in the NHP brain at 7T. Elias Djaballah1, Anojan Uthayakumar2, Martin Bouchet 1, André Kalouguine1, Alexis Amadon2, and Qi ZHU1 1Cognitive Neuroimaging Unit, INSERM, CEA, Université Paris-Saclay, NeuroSpin Center, GIF-SUR-YVETTE, France, 2BAOBAB, Université Paris-Saclay, CEA/Joliot/NeuroSpin, GIF-SUR-YVETTE, France Keywords: Shims, High-Field MRI, non-human primate, B0 shimming, fMRI Motivation: Functional MRI faces challenges due to B0 field inhomogeneities, which are amplified in non-human primate studies, especially at ultra-high fields. Goal(s): Our aim was to develop a Multi-Coil Array (MCA) specifically designed for whole brain shimming of non-human primates. Approach: A semi-heuristic approach was used to design an MCA, based on the Principal Components Analysis of subject-optimal stream functions. The MCA was then constructed and used to image an in-vivo NHP brain. Results: The designed MCA effectively reduced B0 inhomogeneities in the primate brain, resulting in significant improvements in B0 homogenization and enhanced image quality in functional MRI images at 7T. Impact: The development of a Multi-Coil Shim Array designed specifically for non-human primates significantly improves functional MRI image quality by effectively reducing B0 inhomogeneities. This advancement could pave the way for more accurate and detailed primate brain studies at ultra-high fields. |
08:15 | 0476.
| Development of the H12 insertable head gradient set designed for 10.5T and optimized for both peripheral nerve stimulation and magnet heating Brian Rutt1, Peter Roemer2, Andrew Alejski3, Trevor Wade3, Matthew Bester3, Koray Ertan4, Alexander Bratch5, Gregor Adriany5, and Kamil Ugurbil5 1Radiology, Stanford University, Stanford, CA, United States, 2Roemer Consulting, Lutz, FL, United States, 3Robarts Research Institute, University of Western Ontario, London, ON, Canada, 4Stanford University, Stanford, CA, United States, 5CMRR, University of Minnesota, Minneapolis, MN, United States Keywords: Gradients, Gradients, Peripheral nerve stimulation, magnet heating Motivation: Two interactions between gradient coils and their environment severely limit imaging performance: stimulation of peripheral nerves in human subjects and deposition of heat energy into the superconducting main magnet leading to helium loss or quench. This heating increases significantly for higher B0 and gradient switching frequencies. Goal(s): To address the above limitations by recasting the gradient design problem in a unique way to simultaneously minimize both of these interactions. Approach: Using these new methods, we designed and modeled a head gradient coil: H12. Results: We achieved >1.4 fold PNS improvement and >6 fold lower magnet heating compared to existing state-of-the-art head gradient coils. Impact: Our method allows the design and
real-world use of stronger and faster-switching gradients than any in existence,
while minimizing peripheral nerve stimulation and excessive magnet heating. The
potential impact is especially high for head gradients operating at ultra high
field. |
08:15 | 0477.
| Efficient RF Shimming Strategies for Cardiac MRI at 5T Jiaxu Li1,2,3, Nan Li1,2, Liqiang Zhou4, Zhenhua Shen4, Shengping Liu3, Xiaoliang Zhang5, and Ye Li1,2 1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 2Key Laboratory for Magnetic Resonance and Multimodality lmaging of Guangdong Province, Shenzhen, China, 3Chongqing University of Technology, Chongqing, China, 4United lmaging Healthcare, Shanghai, China, 5Department of Biomedical Engineering, State University of New York at Buffalo, New York, NY, United States Keywords: Parallel Transmit & Multiband, Parallel Transmit & Multiband, SAR;RF Shimming;CMR; Motivation: Enhance RF shim efficiency, reduce power, and provide uniformity for ultra-high field cardiac imaging. Goal(s): To significantly enhance excitation efficiency, reduce excitation power, and mitigate the risk of SAR exceeding safe levels, while minimizing loss of uniformity. Approach: Optimizing excitation intensity and uniformity through joint loss function and validating the approach with simulation models and in vivo imaging. Results: The research results indicate that, when compared to MLS, the proposed Eff-MLS leads to an average 3.3% reduction in CV, while improving safety excitation efficiency by 442.26% in the simulation model. Similar effects were also observed in in-vivo experiments. Impact: By enhancing RF shim efficiency and reducing the required excitation power while maintaining uniformity, this approach paves the way for more precise, high-resolution cardiac imaging at ultra-high field strengths. The potential impact includes broader applications of ultra-high field CMR. |
08:15 | 0478.
| Local SAR comparison of leg positioning in 16-channel proton/sodium dipole/loop array for 7T MRI Menglu Wu1, Jessica M Winfield2,3, Pete Lally4,5, and Ozlem Ipek1 1King's College London, London, United Kingdom, 2Department of Physics, The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom, 3Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, United Kingdom, 4Department of Bioengineering, Imperial College London, London, United Kingdom, 5London Collaborative Ultra high field System (LoCUS), London, United Kingdom Keywords: Safety, Safety Motivation: Sodium(23Na)/proton(1H) MRI of the extremities have great potential in diagnosis and treatment of musculoskeletal conditions and oncology applications (e.g.soft-tissue sarcomas). Goal(s): Assessing the performance of a novel 16-channel 1H/23Na MRI coil across varied leg positions and establish safe RF power limits for clinical applications. Approach: Electromagnetic simulations to analyse coil performance in four leg positions. SAR10g levels were compared across configurations while maintaining B1+ field efficacy. Results: The coil showed consistent B1+ performance across all tested positions. The highest SAR levels occurred with calf-to-coil contact, aligning with predictions. Safe RF power limits were established, supporting the coil's clinical potential for extremity imaging Impact: This study validates an innovative 16-channel 1H/23Na coil,
setting benchmarks for safe RF power limits, and enhancing disease characterisation,
enabling clinical research in musculoskeletal pathologies and soft-tissue sarcoma
in the extremities. |
08:15 | 0479.
| Evaluation of a Numerical Approach Alternative to MR Thermometry in the Safety Validation of Multi-Channel RF Coils Alireza Sadeghi-Tarakameh1, Simon Schmidt1, Matt Waks1, Russell L Lagore1, Nur Izzati Huda Zulkarnain1, Xiaoping Wu1, Gregor Adriany1, Gregory J Metzger1, Kamil Ugurbil1, and Yigitcan Eryaman1 1Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, MN, United States Keywords: Safety, Safety Motivation: The existing safety validation process for multi-channel RF coils requires MR thermometry tests, which are difficult to carry out. Goal(s): To propose an alternative approach to MRT in the validation process of multi-channel RF coils. Approach: The simulated B1+ error was measured and propagated to the SAR error using Monte-Carlo simulations. To validate this approach MRT experiments were conducted with a 16-channel body coil at 10.5T, and the measured SAR errors were compared against the predicted ones. Results: For two different excitation patterns, measured SAR errors were 36% and 40%, while predicted SAR errors were 49% and 46%, respectively. Impact: The new strategy presented replaces MR
Thermometry in the safety validation process of multi-channel RF coils. This approach
can simplify and accelerate the development and testing of innovative
multi-channel RF coils which are essential for UHF MRI applications. |
08:15 | 0480.
| SAR safety procedure for self-built pTx human head RF array coils at 9.4T Felix Glang1, Dario Bosch1,2, Georgiy Solomakha1, Jonas Bause1, Nikolai I Avdievich1, and Klaus Scheffler1,2 1Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany Keywords: Safety, High-Field MRI, SAR, EM simulation Motivation: Ensuring subject safety, in particular to limit tissue heating, is a critical aspect of self-developed pTx RF array coils for UHF applications.
Goal(s): Establishing a dependable workflow for accurate simulation, data processing and realization of online supervision of power deposition. Approach: The workflow relies on cross-comparisons of EM simulation results and intermediate processing steps based on representative excitation modes, and on comparison of measured and simulated field maps. Results: Consistency was achieved in all cross-comparison steps. Residual discrepancies between measured and simulated B1+ maps require further investigation, but their safety implications can be addressed by an appropriate safety factor. Impact: A reliable workflow for EM simulation,
subsequent data processing, and realization of online SAR monitoring for
home-built RF human head array coils at 9.4T is presented. This is an essential
building block to ensure subject safety in experimental UHF studies. |
08:15 | 0481.
| Safety of Implanted Auditory Prostheses at 7T Guy Fierens1,2,3, Matthew Clemence4, Nicolas Verhaert3,5, Richard Bowtell6,7, and Rebecca Susan Dewey6,7,8 1Cochlear Technology Centre Belgium, Mechelen, Belgium, 2Laboratory of Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Leuven, Belgium, 3Research group Experimental Otorhinolaryngology, Department of Neurosciences, KU Leuven, Leuven, Belgium, 4Philips Healthcare N. V., Best, Netherlands, 5Department of Otolaryngology, Head and Neck Surgery, University Hospitals Leuven, Leuven, Belgium, 6Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom, 7National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, Nottingham, United Kingdom, 8Hearing Sciences, Division of Mental Health and Clinical Neurosciences, School of Medicine, University of Nottingham, Nottingham, United Kingdom Keywords: Safety, Safety, Prostheses, active auditory implants Motivation: While scanning individuals with active hearing implants (e.g., cochlear implants) at 1.5 and 3 T has become commonplace, scanning these patients at ultra-high field strengths (e.g., 7 T) is likely to be associated with an increased risks of damaging the device or causing soft-tissue damage, pain, and/or discomfort. Goal(s): To evaluate the safety of three different active hearing implants in the 7 T MR environment. Approach: Five potential interactions between the devices and the MR environment were assessed using industry-recommended practices for 1.5/3 T. Results: Preliminary findings show no adverse effects within the predefined test conditions. Impact: While scanning individuals with active hearing implants at
1.5/3 T has become commonplace, 7 T is associated with significantly
greater safety risks. This study is the first to provide some confidence in the safety of such
implants at 7 T. |
08:15 | 0482.
| Whole brain mapping of NAD at 7T using a 31P 32-channel array coil Zhiwei Huang1,2, Mark Widmaier1,2, Daniel Wenz1,2, Uzay Emir3, and Lijing Xin1,2 1CIBM Center for Biomedical Imaging (CIBM), Ecublens, Switzerland, 2Animal Imaging and Technology, Ecole Polytechnique Fédérale de Lausanne (EPFL), Ecublens, Switzerland, 3School of Health Sciences, College of Health and Human Sciences, Purdue University, West Lafayette, IN, United States Keywords: Spectroscopy, Spectroscopy, 31P MRSI, NAD+, NADH Motivation: Nicotinamide adenine dinucleotide (NAD) is vital in cellular metabolism, existing in an oxidized (NAD+) and reduced (NADH) form. Its submillimolar concentration in the human brain makes its whole brain mapping challenging. Goal(s): To explore the feasibility of whole-brain NAD mapping in human. Approach: 31P MRSI data were acquired from two volunteers using a 31P 32-channel array coil at 7T. Metabolites were quantified with LCModel. Results: 3D whole-brain NAD maps were acquired with decent SNR within 45min. The measured NAD level and NAD+/NADH ratio were stable across two subjects and aligned with previous single-voxel studies. Impact: Our preliminary data
demonstrated the feasibility of whole-brain NAD mapping in humans at 7T, which offers the potential to study regional-specific bioenergetics under different pathological
conditions. |