| 13:30 | 0904.
 | Connectome 2.0: Performance evaluation and initial in vivo human brain diffusion MRI results Gabriel Ramos-Llordén1, Peter Dietz2, Mathias Davids1, Hong-Hsi Lee1, Yixin Ma1, Mirsad Mahmutovic3, Alina Scholz3, Hansol Lee1, Chiara Maffei1, Anastasia Yendiki1, Berkin Bilgic1, John E. Kirsch1, Daniel J. Park1, Bryan Clifford4, Wei-Ching Lo4, Stefan Stocker2, Jasmine Fischer2, Elmar Rummert2, Andreas Krug2, Andreas Potthast2, Thomas Benner2, Rebecca Ramb2, Peter J. Basser5, Thomas Witzel6, Lawrence L. Wald1, Bruce R. Rosen1, Boris Keil3,7, and Susie Y. Huang1
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, United States, 2Siemens Healthineers, Erlangen, Germany, 3Institute of Medical Physics and Radiation Protection, Mittelhessen University of Applied Sciences, Giessen, Germany, 4Siemens Medical Solutions USA, Boston, MA, United States, 5Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States, 6Q Bio Inc, San Carlos, CA, United States, 7Department of Diagnostic and Interventional Radiology, University Hospital Marburg, Philipps University of Marburg, Marburg, Germany Keywords: Gradients, Gradients, Diffusion Acquisition, Neuro Motivation: Current human MR scanners cannot resolve the full range of length scales needed to study the brain's microscopic and mesoscopic structure. Goal(s): To construct and validate the next-generation human connectomics and microstructure MRI scanner known as Connectome 2.0. Approach: The 3T Connectome 2.0 scanner incorporates a peripheral nerve stimulation-optimized asymmetric head gradient driven by dual gradient power amplifiers. Custom-built high-sensitivity 72-channel (in vivo imaging) and 64-channel (ex vivo imaging) receive coils were integrated. Results: The Connectome 2.0 scanner achieves Gmax=500 mT/m and SRmax=600 T/m/s, demonstrates 2x improved SNR for diffusion MRI over Connectome 1.0, and enables high-resolution tractography. Impact: The Connectome 2.0 scanner will allow the exploration of new microstructure properties and connectional anatomy in the living human brain with unprecedented spatial and diffusion resolution. |
| 13:42 | 0905.
 | A Versatile Setup for Measuring Complex Gradient-to-Acoustic-Noise or Gradient-to-Vibration Transfer Functions via the Scanner’s ADC Roland Müller1, Toralf Mildner1, Niklas Wallstein1, and Harald E. Möller1,2
1NMR Methods & Development Group, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2Felix Bloch Institute for Solid State Physics, Leipzig University, Leipzig, Germany Keywords: Gradients, New Devices, Acoustic, Vibration, Microphone, Accelerometer, Transfer Function, Sound Level, Safety Motivation: Knowledge of gradient transfer functions in situ would allow predictions about the auditory spectrum of arbitrary MRI sequences during execution, to achieve individualized assessments of potentially harmful sound levels or damaging vibrations of the gradient coil. Goal(s): Our goal was to enable the integration of appropriate sound or vibration measurements into the routine operation of a scanner. Approach: A modulator box was developed that emulates a receiver coil and permits the simultaneous digitization of variable sensor signals (e.g., microphones and accelerometers) by the scanner's ADC. Results: Realistic gradient-to-acoustic-noise and gradient-to-vibration transfer functions were determined without the need of synchronizing external devices. Impact: A versatile
hardware concept has been developed that allows integration into a
clinical scanner and prediction of the sound level inside the bore
from the frequency spectrum of the input signal defined by the pulse
sequence during scanning. |
| 13:54 | 0906.
 | Impact of third order shim coils on gradient-magnet interactions and gradient waveform fidelity Nicolas Boulant1, Caroline Le Ster1, Alexis Amadon1, Guy Aubert2, Alexander Beckett3,4, Jean Belorgey2, Cédric Bonnelye1, Dario Bosch5,6, David Otto Brunner7, Guillaume Dilasser2, Olivier Dubois2, Philipp Ehses8, David Feinberg3,9, Sajjad Feizollah10, Vincent Gras1, Simon Gross7, Quentin Guihard2, Hervé Lannou2, Denis Le Bihan1, Franck Mauconduit1, Frédéric Molinié2, François Nunio2, Klaas Pruessmann11,12, Lionel Quettier2, Klaus Scheffler5,13, Tony Stöcker8, Christine Tardif10, Kamil Ugurbil14, Alexandre Vignaud1, An Vu15,16, and Xiaoping Wu14
1NeuroSpin, CEA, Gif sur Yvette, France, 2Irfu, CEA, Gif sur Yvette, France, 3Advanced MRI technologies, Sebastopol, CA, United States, 4Helen Wills Neuroscience institute, University of California, Berkeley, CA, United States, 5Department for biomedical Magnetic Resonance, University of Tübingen, Tuebingen, Germany, 6High-field MR center, Max Planck Institute for biological cybernetics, Tuebingen, Germany, 7Skope MRT, Zürich, Switzerland, 8DZNE, Bonn, Germany, 9Helen Wills Neuroscience institute, Universiy of California, Berkeley, CA, United States, 10Montreal Neurological Institute-Hospital, McGill University, Montreal, QC, Canada, 11ETH Zürich, Zürich, Switzerland, 12University of Zürich, Zürich, Switzerland, 13High field MR center, Max Planck Institute for biological cybernetics, Tuebingen, Germany, 14Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 15University of California, San Francisco, CA, United States, 16San Francisco VA Health Care System, San Francisco, CA, United States Keywords: Gradients, Gradients Motivation: Third order shim coils can impact gradient-magnet interactions with consequences on image quality and magnet safety. Goal(s): To demonstrate the influence of third order shim coils on the SC72 gradient coil using field and vibration measurements. Approach: The gradient transfer function was measured at 11.7T (Iseult) and at 7T (Terra) with and without connection of the 3rd order shim coils. Vibration measurements were carried out on Iseult from 0 to 11.7T in the two configurations as well. Results: The data demonstrate a drastic influence of the 3rd order shim coils and their circuits. Impact: The work suggests caution when using third
order shim coils at 7T and above. It also paves the way for further
investigations to improve gradient waveform fidelity. |
| 14:06 | 0907.
 | A Magnetic Vector Potential-Based Linear Predictor to Increase Peripheral Nerve Stimulation Thresholds in Gradient Coil Design Liyi Kang1,2, Ling Xia1, Qian Liu3, Qinwei Zhang4, Jianmin Yuan3, and Dan Wu1,2
1Department of Biomedical Engineering, Zhejiang University, Hangzhou, China, 2Center for Intelligent Biomedical Instrumentation, Zhejiang University Binjiang Research Institute, Hangzhou, China, 3United Imaging Healthcare Co., Ltd, Shanghai, China, 4Beijing United Imaging Research Institute of Intelligent Imaging, Beijing, China Keywords: Gradients, Gradients, Gradient coil design, peripheral nerve stimulation, MRI safety Motivation: The linear predictor incorporating a coupled electromagnetic-neurodynamic model shows reliable estimation of Peripheral Nerve Stimulation (PNS) thresholds, which is important for gradient coil design. However, the computational complexity and long computation time within the coupled model leads to difficulties in application. Goal(s): We proposed a simplified predictor based on the spatial distribution of magnetic fields, circumventing complexity of the coupled model. Approach: The magnetic vector potential was employed to form a simplified predictor, serving as a constraint for PNS-optimized gradient coil design. Results: With the simplified predictor, the optimized coil achieved an 84% increase in PNS threshold at a 10% inductance penalty. Impact: Based on the magnetic vector potential, the proposed predictor enabled the simplified evaluation of PNS thresholds through magnetic field spatial distribution. In addition, the proposed method facilitated PNS optimization in gradient coil design. |
| 14:18 | 0908.
 | Concept 0.13 T bedside MRI for early brain imaging in the neonatal intensive care unit. Aaron R. Purchase1,2,3, Monika Sliwiak1, Sara V. Bates3,4, Jason P. Stockmann1,3, Martin D. Hurlimann1,3, Lawrence L. Wald1,3,5, and Clarissa Z. Cooley1,3
1A.A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 2Radiology, Massachusetts General Hospital, Boston, MA, United States, 3Harvard Medical School, Boston, MA, United States, 4Pediatrics-Neonatology, Massachusetts General Hospital, Boston, MA, United States, 5Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States Keywords: Magnets (B0), Magnets (B0) Motivation: Despite the high diagnostic value of MRI, safety concerns and logistical burdens often prohibit the transport of neonatal intensive care unit (NICU) patients to standard MRI scanners. Goal(s): In response, we aim to design a specialized NICU bedside MRI scanner that prioritizes minimal disruption to care and provides a higher field strength (and signal-to-noise) than currently available portable scanners. Approach: Using realistic finite element modeling and genetic algorithm optimization, we demonstrate a 131mT Halbach magnet design with a peak-to-peak homogeneity of 421ppm over a 14cm diameter spherical volume. Results: We present the computer-aided-design prototype of the full portable NICU MRI system. Impact: The bedside MRI scanner capable of diffusion contrast neuroimaging of neonates could bring a new early evaluation tool for brain conditions such as hypoxic ischemic encephalopathy (HIE). |
| 14:30 | 0909.
 | Design, construction and first experimental results of the high performance LH7 insertable head gradient set at 10.5T Brian Rutt1, Alexander Bratch2, Andrew Alejski3, Trevor Wade3, Matthew Bester3, Koray Ertan4, Peter Roemer5, Edward Auerbach2, Gregor Adriany2, and Kamil Ugurbil2
1Radiology, Stanford University, Stanford, CA, United States, 2CMRR, University of Minnesota, Minneapolis, MN, United States, 3Robarts Research Institute, University of Western Ontario, London, ON, Canada, 4Stanford University, Stanford, CA, United States, 5Roemer Consulting, Lutz, FL, United States Keywords: Gradients, Gradients, ultra high field, insertable head gradient, PNS Motivation: Increased gradient performance can address several of technical and physics challenges of UHF MRI. Goal(s): To develop a head gradient coil (known as LH7) for insertion into the body gradient coil of a 10.5T MRI system. Approach: Design innovations include: symmetric folded geometry with variable end-flange angle optimized for shoulder geometry; double Z-primary layer. Results: With 650A, 2000V gradient drivers, the hardware limits of LH7 are Gmax 117mT/m and Smax 900T/m/s. Thermal results demonstrate cooling capacity >45kW. Compared to body gradients, PNS thresholds are 2-3 fold higher. After interfacing LH7 to the CMRR 10.5T, promising experimental characterizations and imaging results have been obtained. Impact: LH7
provides an order-of-magnitude increase in head gradient performance (Gmax*Smax) over body gradients, which, combined
with 10.5T B0, should provide major sensitivity and resolution
increases for brain mapping by dMRI or fMRI. Experimental results to date are
confirming these expectations. |
| 14:42 | 0910.
 | Leveraging unprecedented ultra-high strength gradients in commercially available MRI for in-vivo diffusion tensor CMR Andrew D Scott1,2, Karl P Kunze3, Pedro F Ferreira1,2, Peter Speier4, Christian Geppert4, Dudley J Pennell1,2, and Sonia Nielles-Vallespin1,2
1CMR Unit, The Royal Brompton Hospital, London, United Kingdom, 2National Heart and Lung Institute, Imperial College London, London, United Kingdom, 3MR Research Collaborations, Siemens Healthcare Limited, Camberley, United Kingdom, 4Cardiovascular MR Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany Keywords: Gradients, Diffusion Tensor Imaging, ultra high gradient strength; motion compensated spin echo; Motivation: Spin echo diffusion tensor cardiovascular magnetic resonance (DT-CMR) suffers from low SNR and resolution due to the time-consuming motion-compensated encoding gradients required. Goal(s): Shorten TEs for motion compensated spin echo (MCSE) DT-CMR techniques to improve SNR and allow higher spatial resolution using ultra-high strength whole body gradients (200mT/m) newly available in commercially available scanners. Approach: We implemented second order MCSE and acquired data in healthy subjects at peak systole and end diastole with maximum gradient strength of 146mT/m. Results: We demonstrate high quality MCSE DT-CMR data with reduced TEs and higher spatial resolution than on previously available scanners using similar protocols. Impact: Increases in imaging efficiency in DT-CMR enabled by the use of ultra-high strength gradients on commercial MRI systems will deliver shorter scans and improvements in spatial resolution which are vital steps on the road to clinical translation of DT-CMR. |
| 14:54 | 0911.
 | Accelerating MRI with a Wireless Insert Gradient Coil Edwin Versteeg1, Rik Weersink1,2,3, Sven Nouwens3, Thomas Roos1, Jeroen Siero1, and Dennis Klomp1
1Department of Radiology, UMC Utrecht, Utrecht, Netherlands, 2Department of Biomedical Engineering, Technical University Eindhoven, Eindhoven, Netherlands, 3Department of Mechanical Engineering, Technical University of Eindhoven, Utrecht, Netherlands Keywords: Gradients, Gradients Motivation: High performance gradients enable fast and high-resolution imaging but are costly and cumbersome to install in an existing MRI-system Goal(s): Present a wireless (resonant) gradient coil setup that yields additional gradient performance without needing a dedicated amplifier Approach: The increased gradient performance was measured using field camera measurements and acceleration performance was assessed retrospectively using phantom experiments Results: The wireless gradient yielded a factor 23 improvement in slew rate (from 125 T/m/s to 2900 T/m/s) and 28-fold retrospective acceleration resulted in aliasing free images. Impact: A wireless insert
gradient coil enables 28-fold accelerated scanning without a supplementary
gradient amplifier. This provides a cost-effective pathway for improving gradient
performance with minimal system modifications. |
| 15:06 | 0912.
 | Safe Diffusion Lobes for Diminished Gradient Vibration Matthew A. McCready1, John Pauly1, and Adam B Kerr1,2
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Center for Cognitive and Neurobiological Imaging, Stanford University, Stanford, CA, United States Keywords: Pulse Sequence Design, Pulse Sequence Design Motivation: Gradient coil vibrations are a source of loud acoustics, persistent field distortions, potential system damage, and in some cases signal dropout in diffusion MRI. Vibrations are particularly strong at mechanical resonant frequencies. Goal(s): To design “safe” time-optimal diffusion gradients which avoid mechanical resonant frequencies. Approach: A convex optimization problem is formed which seeks to maximize b-value for a given duration while constraining the discrete cosine transform of the diffusion lobe. A bisection search is applied to duration to find the shortest feasible solution with the target b-value. Results: Safe diffusion lobes greatly diminished coil vibration and minimized oscillations in the gradient fields. Impact: Safe diffusion lobes were shown to avoid specified gradient mechanical resonant
frequencies reducing vibrations and persistent k-space oscillations. These
waveforms have clinical and research potential to improve auditory comfort, prevent
DWI signal dropout and image artifacts, and prevent system damage. |
| 15:18 | | DiscussionFeng Liu University of Queensland, Australia |