ISMRM 25th Annual Meeting & Exhibition • 22-27 April 2017 • Honolulu, HI, USA

 2654 -2674 RF Coils & Systems 2675 -2697 Gradient, Shim & Magnet Technology 2698 -2718 Hybrid & Novel Technology

RF Coils & Systems
Engineering

Wednesday, 26 April 2017
 Exhibition Hall 16:15 - 18:15

 2654 A high density 24 channel array coil extendable to 48 channels for human cortical MRI at 7T. Alexander Beckett, An Vu, Scott Schillak, Lawrence Wald, David Feinberg Coil arrays using smaller loop sizes allow increased signal close to the coil array. Such coil arrays with a large number of channels allow increased SNR across a large area of cortex, and accelerated imaging comparable to commercially available high-channel coils, with particularly good performance close to the coil array. These gains in SNR allow high-resolution (0.5mm isotropic) EPI 2655 Towards a Flexible Transceiver Array for 7 T Cardiac MRI: Evaluation of Decoupling Ring Effects Sajad Hosseinnezhadian, Roberta Frass-Kriegl, Sigrun Goluch, Michael Pichler, Jürgen Sieg, Marie Poirier-Quinot, Luc Darrasse, Ewald Moser, Jean-Christophe Ginefri, Elmar Laistler In view of building a flexible 7T 2D coil array for cardiac MRI at 7 T, transmission line resonators (TLRs) with and without decoupling ring are investigated. Using 3D EM simulation and MR measurements for single elements, it could be shown that the presence of the decoupling ring does not perturb significantly the  $$B_1^+/\sqrt{P_{input}}$$distribution of the TLR. 3D gradient echo images for both TLRs with and without decoupling rings have been acquired. No significant degradation in the image quality due to the presence of the decoupling ring was observed. 2656 A Sixteen-Channel Array Coil for Carbon-13 Spectroscopy of the Breast at 7T Matthew Wilcox, Stephen Ogier, Sergey Cheshkov, Ivan Dimitrov, Craig Malloy, Steven Wright, Mary McDougall Biomarkers detectable by carbon-13 NMR spectroscopy have known correlations with breast cancer characterization, but in vivo 13C spectroscopy has been limited by low SNR. To counteract this, a 16-element receive coil and isolating preamplifier box was constructed for carbon-13 spectroscopy of the breast at 7 Tesla. The array was characterized on the bench and showed good results in terms of ease of tuning, low element-to-element coupling and Q values. Scanner testing using the coil was preliminary but showed successful 1H and 13C transmission and that array elements were individually able to acquire spectra. 2657 A Modular, Scaleable, and Customizable Phased Array Structure Suitable for Ultra-High Channel Phased Arrays Wolfgang Loew, Christopher Ireland, Matthew Lanier, Brynne Williams, Matthew Batie, Yu Li, Randy Giaquinto, Ron Pratt, Charles Dumoulin A novel three-layer frame was developed to enable scalable phased-array coils. The geometry of the three-layer frame allows a single 12-element tile to dock with up to four identical tiles. When adjacent tiles are docked, the overlap of coils in adjacent tiles is identical to the coil overlap within a tile. Two phased-arrays setups using 12-element tiles and integrated balun coil technology were constructed. The first contained two separate tiles and the second had two interconnected tiles. The phased-array coils were evaluated with phantom imaging experiments and with multiple in-vivo experiments. 2658 Optimal array configuration for cerebral cortex MRI at 7T: six center-fed dipoles with two loops RF coil array Jérémie Clément, Rolf Gruetter, Özlem Ipek Searching for optimal RF coil array for whole-brain MR applications, central-fed dipole was compared with fractionated dipole in a single and RF coil array configurations with combination of loop coils in measurements and electromagnetic field simulations in terms of B1+ transmit efficiency, field uniformity, SAR and mutual coupling in an array. High transmit field performances were shown over the cerebral cortex by using phase-only shimming with six center-fed dipoles with two loops RF coil array on experimentally measured B1+-maps and anatomical MR images. 2659 Structure Adjustment of Surface Dipole Antenna Elements for Body Imaging at 7 Tesla MRI Suchit Kumar, Young-Seung Jo, Jeong-Hee Kim, Chulhyun Lee, Chang-Hyun Oh In ultra-high-field magnetic resonance imaging (UHF-MRI), body imaging suffers from B1 inhomogeneity due to relatively short wavelength. A range of new radio frequency (RF) coil designs has been proposed to overcome this problem. As previously reported, dipole antenna had been proposed to address this B1+ inhomogeneity problem for body imaging. In this paper, structural adjustment of dipole antenna has been tried for parallel transmission to improve overall B1+ homogeneity. Surface dipole antennas with several structures are tried and compared with our top-hat dipole antenna array reported previously. Also, static RF shimming was employed to evaluate the B1 uniformity. 2660 An adjustable 8-channel receive coil for population studies of marmosets Kyle Gilbert, Joseph Gati, Peter Zeman, David Schaeffer, Stefan Everling, Ravi Menon An eight-channel RF coil was developed for imaging the common marmoset at 9.4T. The coil was adjustable in width to accommodate different head sizes while maintaining high SNR, thereby facilitating the study of larger cohorts of animals. Tuning and matching of the coil did not require adjustment over the range of potential head sizes. EPI time series were acquired, showing minimal geometric distortion with a two-fold reduction factor. A two-fold reduction factor could be achieved in both the left-right and anterior-posterior directions. 2661 Fifteen-channel receive coil for high acceleration rates in UHF marmoset imaging Kyle Gilbert, Joseph Gati, L Klassen, Stefan Everling, Ravi Menon A 15-channel receive coil, in conjunction with a 2-channel transmit coil, was developed for imaging the common marmoset at 9.4T. The high channel count produced low geometry factors while accelerating in EPI acquisitions, thereby reducing geometric distortions with minimal impact on the SNR. This demonstrates the utility and feasibility of employing higher channel counts for functional imaging of the marmoset. 2662 A 10-element receive-only RF coil array for imaging the brain of awake marmosets Wen-Yang Chiang, Cecil Yen, Mary McDougall, Afonso Silva A 10-element head RF coil array was developed for imaging the brain of awake marmosets. A soccer ball design was used to improve whole brain coverage and parallel imaging acceleration when compared to our previous designs. Coil clip and PLA cement were introduced to help place the small coil elements on surfaces of irregular shape and optimize geometric decoupling. The matching network provided independent adjustments of tuning, matching, active detune and preamp decoupling, greatly simplifying the construction of coil arrays in space-limited applications. Molded-in foam padding was also introduced to provide additional comfort during awake marmoset imaging. 2663 Ladder and Overlapped Phased Array Coil Comparison for Neck Imaging at 3 Tesla Michael Beck, Dennis Parker, J Hadley A ladder and overlapped phased array coils were constructed with the same number of channels and overall dimensions to see how much of a SNR performance difference there was between the two coil construction techniques. The results show that between 2 and 12 cm within a cylindrical phantom the difference between SNR was less than 3%. With negligible performance difference the ladder array can be a viable alternative to overlapped arrays if a simpler coil construction process is desired. 2664 Quadrature Head Coil for Brain Imaging at 6.5 mT Neha KOONJOO, Bryce Primavera, Jason Stockmann, Thomas Witzel, Lawrence Wald, Matthew Rosen Highly-resolved proton imaging is challenging in the millitesla regime. With the aim of enhancing our previous single-channel spiral head coil for operation at 276 kHz, a quadrature head coil was designed, comprised of 2 layers (inner and outer) producing orthogonal B1 fields. Images acquired with the new quadrature coil had the same signal magnitude when compared to the single-channel coil. However, the expected √2-factor signal enhancement in combined SNR was not fully realized due to a 30% higher noise floor observed in one quadrature. Improvements in gradient amplifier filtering will significantly improve the SNR. 2665 Dual-Tuned RF Coil system for Parallel Imaging of Human Lungs Using Perfluorinated Gases Vishal Kampani, Randall Jones, Hal Charles, Natalie Hussey To create a dual-tuned (1H & 19F) receive-only surface coil array for pulmonary functional imaging. This satisfies an unmet clinical need because there is currently no widely accessible 3D measure of regional lung function. As a result, the current standard of care for diagnosis and evaluation of lung disease relies nearly exclusively on global measures such as spirometry. The technical significance of this proposal is that the implementation of parallel imaging for 19F MRI would provide a means to shorten breath hold times with marginal SNR impact as well as facilitate the development of real time free breathing image acquisitions. 2666 Ultra-high-field CAIPIRINHA modulated parallel transmit excitation for homogenous image reconstruction without RF shimming Iulius Dragonu, Craig Buckley, Matthew Robson, Aaron Hess Ultra-high-field (UHF) provides higher SNR than conventional, clinically available field strengths. However, UHF suffers from heterogeneous transmit B1+ fields. At 7 T, the shortened transmit radio-frequency (RF) wavelengths have a similar value to the dimensions of the human head/thorax which may result in signal cancellation and local signal dropouts. In this paper, we propose a novel imaging scheme based on simultaneous excitation with all transmit channels. Controlled aliasing is used to encode each transmit channel independently which we term Tx-CAIPIRINHA.Tx-CAIPIRINHA has been demonstrated in-vivo. The concept uses the linear superposition of B1+ fields via the excitation flip angle which only holds true in the low flip angle regime. When normalizing to transmit efficiency, Tx-CAIPIRINHA achieved a marginally higher SNR than B1+ shimming, demonstrating the constructive combination of transmit sensitives throughout the image. 2667 Towards Routine Body Imaging at 7T Using a Hybrid Dipole and Birdcage Coil Array Jan Paska, Martijn Cloos, Graham Wiggins Body imaging at 7T is challenging due to wavelength effects, a low sensitivity in deep tissue1, and a large variation in body sizes across the patient population. A common approach is to use close fitting coils or dipoles2,3,4, which exhibit a high transmit and receive sensitivity and are fairly load independent, but lack the easy handling necessary for routine clinical use. We aim to construct an RF coil array for general purpose body imaging for routine use that is robust, easy, and safe to handle, while retaining adequate sensitivity in the deeper regions. Given these boundary conditions, we settled on a stand-off design5 with an RF shield. Thus, consciously sacrificing some sensitivity to improve handling and safety. After extensive optimization we converged to an optimal coil array consisting of a transceive dipole array complemented with a birdcage array for reception only. The array was completed and a sensitivity analysis with respect to body sizes was performed. 2668 An RF birdcage coil designed for an insert gradient coil dedicated to short-T2 MRI Manuela Rösler, Markus Weiger, David Brunner, Thomas Schmid, Romain Froidevaux, Klaas Pruessmann Two major challenges for MRI of short-T2 tissues are creating large gradient strengths and avoiding signal contamination from hardware parts, in particular the RF coils. In this work, to enable short-T2 MRI with a dedicated insert gradient coil, an RF birdcage coil was designed with a) minimized background signal and b) optimized B1 field to prevent aliasing associated with the limited monotonic range of the gradient. 2669 Multiple-Mouse Magnetic Resonance Imaging with CryoProbes Aidin Arbabi, Dulcie Vousden, Leigh Spencer Noakes, Jun Dazai, Shoshana Spring, John Sled, Jason Lerch, Mark Henkelman, Brian Nieman Multiple-mouse MRI was implemented on a 7-Tesla magnet with four Cryogen (liquid helium)-cooled radio frequency probes. The high signal-to-noise ratio offered by the probes enabled spatial resolutions of 60 μm isotropic in <2 hours, a significant improvement for in vivo anatomical imaging of the mouse brain. Several 3D pulse sequences including FLASH/MP2RAGE/RARE were implemented for multiple-mouse acquisition. Manganese-enhanced T1-weighted images were obtained at two different resolutions of 60 μm and 75 μm. Results demonstrate the combined benefits of cryogen-cooled coils and multiple-mouse MRI. 2670 An SNR Optimized Quadrature Reception Posterior Array for Prostate Imaging at 3 Tesla Jorge Chacon-Caldera, Alexander Fischer, Matthias Malzacher, Lothar Schad Increasing signal-to-noise-ratio (SNR) in prostate MRI could facilitate the diagnosis and characterization of prostate cancers. In this work, we built a quadrature posterior surface array that aims to increase local SNR at the prostate. The coil was compared to 3 and 9 channels of the standard spine array using phantom measurements. Respectively, SNR gains of 12 and 9% were obtained using a realistic region-of-interest (ROI). Further work will be undertaken to translate the SNR gains to in-vivo prostate imaging at 3T. 2671 New design of flexible surface coil with variodes and remote detuning Wenming Li, Shu Du, Jianmin Wang New design of flexible surface coil was presented. Voltage-controlled variodes instead of trimmers are used for remote coil frequency adjustment; λ/4 impedance transforming circuit are used to enable remote detune, thus detune circuits with big rigid components are moved out from the antenna part. By doing this, the antenna is covered by soft foam seamlessly which improved the flexibility significantly. Design was tested on four-element arrays. Experiments on both phantom and invivo testing show good results with this design. 2672 Human Brain Imaging at 7T With On-coil Transceivers Natalia Gudino, Qi Duan, Jacco de Zwart, Stephen Dodd, Joe Murphy-Boesch, Peter van Gelderen, Jeff Duyn On-coil current-source switch-mode amplification presents high power efficiency, allows direct control of the transmit field (B1), and decoupling of elements through the amplifier output impedance. These are important advantages over conventional remote voltage-mode quasilinear amplification that should allow more efficient and safer implementation of a multi-channel transmit system. Following this approach, we present an optically controlled transceiver design that was used for initial safety assessment of the technology toward the implementation of a high channel-count pTx array for brain imaging at high-field. We acquired human brain images with this technology at 7T 2673 An adjustable field-of-view rung element for 7T transmit array coils using forced current excitation Jiaming Cui, Chenhao Sun, Dheyaa Alkandari, Steven Wright This abstract reports a switchable coil element which uses “forced current excitation”. The coil consists of three aligned rungs, with a total length of 37 cm. Any one or more of three rungs can be easily selected to provide a variable length or position field-of-view. The forced current approach ensures equal current on the selected rungs to give a uniform field distribution along the length of the field-of-view. Bench measurements demonstrate the expected efficiency improvement when only a single rung is selected and the uniform field pattern. 2674 Optimization via Ultra-high Permittivity Materials of Pad Effects in Dielectric Shimming at 7 Tesla MRI Ana Luisa Neves, Redha Abdeddaim, Stefan Enoch, Jerome Wenger, Johann Berthelot, Anne-Lise Adenot-Engelvin, Nicolas Mallejac, Franck Mauconduit, Lisa Leroi, Alexandre Vignaud, Pierre Sabouroux The influence of air fraction on the permittivity of BaTiO3 aqueous mixtures was assessed, with the aim of obtaining high permittivity mixtures. For extremely saturated mixtures (>50%v/v), the air fraction of the mixture plays a great role in determining εr, and by applying high pressure it is possible to go beyond the maximal value described in dielectric shimming literature. A BaTiO3 1cm-thick pad was manufactured (εr =470) and tested in a 7T MRI, as well as a conventional saturated pad (≈40%v/v, εr=200). Results show an overall signal improvement when using higher permittivity pads and the possibility to reduce pad-thickness. Gradient, Shim & Magnet Technology Traditional Poster Engineering Wednesday, 26 April 2017  Exhibition Hall 16:15 - 18:15  2675 Detailing and Enhancing Respiratory Motion Induced Myocardial B0 Field Dispersion at 7.0 T: Implications for Cardiac Imaging and Spectroscopy at Ultrahigh Magnetic Field Strengths Till Huelnhagen, Ariane Fillmer, Antje Els, Florian Schubert, Bernd Ittermann, Thoralf Niendorf Respiratory motion induced B0 field fluctuations, constitute a challenge for B0 sensitive CMR like spectroscopy. Accommodating CMRS in a single breath-hold is elusive if not prohibitive. Motion corrected approaches under free breathing were demonstrated to substantially improve CMRS. Yet, B0 field fluctuations over the respiratory cycle may compromise spectral resolution and data integrity. A compensation strategy like dynamically updated first order shims synchronized with the respiratory motion, offers the potential to enhance spectral quality and permits scan time shortening. This work details respiratory motion induced B0 fluctuations in the interventricular septum and examines the capability of linear shimming for compensation of myocardial B0 fluctuations. 2676 Unilateral Linear Halbach magnets for single sided magnetic resonance: generalized design framework and experimental validation Ashvin Bashyam, Matthew Li, Michael Cima Single-sided NMR has the potential for broad utility, especially as a portable diagnostic for disorders in fluid regulation. These sensors require a remote, high field, uniform magnetic field to achieve sufficient sensitivity. We demonstrate a new magnet geometry, the Unilateral Linear Halbach, that combines design principles from sweet-spot and linear Halbach magnets to achieve this goal. Sensitivity analysis using finite element analysis produces a generalized framework for Unilateral Linear Halbach design. Experimental validation through the fabrication of a magnet assembly shows close agreement with the simulated magnetic field. Unilateral Linear Halbach magnets increase the sensitivity, portability, and versatility of single sided NMR. 2677 A new human-scale fast field-cycling MRI system for clinical applications Peter Ross, Lionel Broche, Gareth Davies, David Lurie Fast-field cycling MRI is a novel technique that involves cycling the main magnetic field during image acquisition. By doing this, information on the magnetic field dependence of parameters such as the T1relaxation time can be investigated and exploited as a new form of endogenous image contrast. In this abstract we present progress on a new human-scale fast field-cycling MRI system with a detection field of 0.2 T. 2678 Towards ultimate air-core magnetometer sensitivity for ultra-low field MRI: A design method Ruben Pellicer-Guridi, Michael Vogel, David Reutens, Viktor Vegh Superconducting quantum interference devices (SQUIDs) are highly sensitive magnetometers and they have found application in ultra-low field MRI. However, they require cryogenics and their noise performance is hindered by external noise sources and the strong fields employed in pre-polarised MRI experiments. Air-core magnetometers provide an attractive alternative, as they are highly sensitive, robust and relatively cheap to manufacture. Our goal is to provide of a method to optimise the sensitivity of these devices. In this work we propose an accurate numerical model and the use of a genetic algorithm to consider previously unexplored coil configurations. 2679 Preliminary Metamaterial Design and Fabrication for MRI at 3T Chao Luo, Xiaoqing Hu, Xiaoliang Zhang, Xin Liu, Ye Li In this paper, we designed and fabricated a kind of metamaterial with 9×9 cells, which bent on phantom and inserted to a birdcage volume coil to investigate the performance for 3T MRI. The results of simulations and phantom experiments agreed with each other very well indicate that the proposed metamaterial is able to increase the B1+ fields in some region closed to the surface of phantom. This improvement of B1+ fields will benefit to 3T MRI targeted clinical applications. 2680 Dual-layered multi-channel B0 and RF coil setup for an improved shimming performance at 9.4 Tesla Christian Mirkes, G. Shajan, Ali Aghaeifar, Irena Zivkovic, Kai Buckenmaier, Klaus Scheffler Multiple local shim coils can be used to improve the B0 homogeneity at ultra-high field. In this work, a dual-layered multi-channel B0 and RF coil setup is presented that allows a flexible design of the shim coil without influencing the RF performance. It is shown that a 16 channel B0 coil in combination with a standard 2nd order spherical harmonics (SH) shim system can achieve a higher degree of B0homogeneity than a 3rd order SH shim system in the case of whole-brain shimming. 2681 An insert gradient for zero-echo-time imaging with 200 mT/m at full duty cycle Markus Weiger, Johan Overweg, Manuela Rösler, Romain Froidevaux, Franciszek Hennel, Bertram Wilm, Alexander Penn, Urs Sturzenegger, Wout Schuth, Menno Mathlener, Martino Borgo, Peter Boernert, Christoph Leussler, Roger Luechinger, Benjamin Dietrich, Jonas Reber, David Brunner, Thomas Schmid, Laetitia Vionnet, Klaas Pruessmann Zero-echo-time (ZTE) techniques enable imaging of tissues with very short T2s, e.g. bone or myelin. Their performance directly scales with gradient strength G, which depends on the target T2 and spatial resolution. With present-day gradients the spatial resolution for T2s on the order of 100 μs is limited to several millimetres. To improve the resolution, considerably higher gradient strengths are required. As a further challenge of ZTE sequences, the strong gradients are applied with full duty cycle. The goal of this work was to develop a gradient coil that meets these challenges, offering very high amplitude at full duty cycle. 2682 Open-Source Acquisition-speed slice-by-slice controller for 32 coil B0 shimming. Nicolas Arango, Jason Stockmann, Thomas Witzel, Lawrence Wald, Jacob White Accurate B0 shimming with close-fitting coil arrays can improve brain imaging at 3T and 7T, but slice-optimizing the shimming during acquisition requires fast redistribution of dozens of multi-amp coil currents. Our open-source, low-cost (80/channel) driver system can redistribute fifty amps to thirty-two coils in milliseconds, with milliamp accuracy.  The system uses an easily reprogrammed microcontroller, optical fiber isolation, and thirty-two current-feedback coil-drivers (described previously). When used to drive sixty-four slice-specific sets of currents in a novel 32-coil shim array, stretching in an EPI brain scan was substantially reduced, without introducing driver artifacts. 2683 Decoupling Controller Design for Real-time Feedback of B0 Shim Systems Paul Chang, Sahar Nassirpour, Anke Henning Real-time B0 feedback has been shown to be beneficial for the controlling of B0 fluctuations. However, update rates that have been reported are slow (~100ms) and either use pre-emphasis to correct for the coupling and faster dynamics of the system or only use control the frequency We show that for faster update rates (±1ms) pre-emphasis (i.e. dynamic decoupling) is not required and that static decoupling can perform equally well or better. 2684 Dynamic B0 Shim Controller for Digital Pre-emphasis with Sub-millisecond Update Rate Paul Chang, Sahar Nassirpour, Anke Henning High-order dynamic B0 shimming has been shown to improve the shim quality for multi-slice acquisition schemes. However, for gradient intensive sequences, eddy currents become a major problem and pre-emphasis is required. The pre-emphasis can be done flexibly with the use of digital filters as they can drive arbitrary-shaped waveforms and are scalable to a larger number of channels.In this work, we design and implement a system to perform dynamic B0 shimming with digital pre-emphasis with a very fast update rate. The setup is then tested for performing pre-emphasis on a 9.4T scanner. 2685 A scalable, MR compatible temperature measurement and control system David Brunner, Jonas Reber, Simon Gross, Klaas Pruessmann Tight temperature control of various devices is required to guarantee highly stable experimental conditions. E.g. B0 field shifts induced by heating of shim irons or gain changes induced in preamplifiers can be avoided by oven controlling the critical components of the device. Furthermore, a recently presented approach of active shimming with controlled magnetic materials requires tight temperature control of a large count of devices in parallel in the bore.  For such applications, we present a 14 channel, low power, MR compatible temperature measurement and control system which can be parallelized for a scalable channel count. 2686 Minimum Current Ripple in the Gradient Array System by Applying Optimum-Phase Pulse-Width Modulation Pattern Soheil Taraghinia, Koray Ertan, Ergin Atalar Phase-shifted Pulse Width Modulation (PWM) technique is implementable in stacked and parallel configuration of the H-bridge gradient amplifiers. However, in the gradient array systems where one stage amplifier is sufficient to drive each element, phase-shifted PWM is not feasible. In this work, similar technique is implemented by utilization of the coupling between the elements of the array and finding the optimized phases for each channel in order to have minimum current ripples. This method is tested for different gradient fields and high ripple reduction percentages achieved both in simulations and experiments. 2687 A Convertible Magnet Array and Solenoid Coil for a Portable Magnetic Resonance Imaging (MRI) System Zhi Hua Ren, Wenshen Zhou, Shao Ying Huang A magnetic resonance imaging (MRI) for outdoor in-situ scanning is promising for biological studies. Here we propose a portable MRI system in which both the magnet array and the transceiver coil can be physically opened and closed. This is for imaging long objects in situ where cutting the object and fitting it into a bore for scanning is not an option. A convertible magnet array is designed where the force to open and to close the magnet array is minimized based on an analytical solution. Meanwhile, a convertible solenoid coil is proposed as an RF transceiver coil. 2688 An open source PXIe platform for MRI instrumentation development Matthew Bourne, Robin Dykstra, Sergei Obruchkov To lower the entry barrier for MRI system development, an open source PXIe platform consisting of IP for peripheral boards, an associated linux device driver and example system controller and peripheral boards were developed. The design was capable of performing system controller initiated DMA transfers in both directions with a maximum block size of 8MB. The hardware design was greatly simplified by mounting FPGA modules from Avnet onto custom PXIe compatible carrier boards. The modules from Avnet contained a System on a Chip device from Xilinx consisting of a dual core ARM processor and FPGA fabric. 2689 Distributed receivers with hardware-accelerated signal processing: Synchronous acquisition of image data and k-space trajectories Josip Marjanovic, Jonas Reber, Lars Kasper, Benjamin Dietrich, David Brunner, Klaas Pruessmann The demand for higher image quality led to a significant increase in the number of parallel receive coils and to the addition of sensor systems such as magnetic field monitoring probes to MR systems, boosting the demand for many high quality receive channels. Furthermore, new methods increasingly require high acquisition duty cycles and bandwidths setting new requirements on data traffic and real-time capabilities. We present a flexible, scalable receiver system addressing those issues demonstrated on an example of concurrent imaging and field monitoring with real-time processing of synchronized streams of coil and trajectory data, as required by modern reconstruction algorithms. 2690 Sensitive Imaging of Vascular Walls with an Endo-esophageal Wireless Amplified NMR Detector (WAND) Xianchun Zeng, Chunqi Qian To improve the detection sensitivity of MRI, a Wireless Amplified NMR Detector (WAND) is developed to image surrounding vessels from inside the esophagus. This cylindrical detector is a double frequency resonator with a single metal wire that is self-connected by a pair of varactors. It can convert wirelessly provided pumping power into amplified MR signals. When the detector is inserted inside the esophagus, vessel walls of the vertebrate artery and basal artery can be identified with greatly improved clarity. This detector will be useful to characterize subtle lesions in inflamed vessels. 2691 Low IF Passive Mixer Topologies for Low Power MRI Front Ends Andreas Port, John Pauly, Fraser Robb, Greig Scott As MRI array counts expand, there is growing interest in moving more of the receive electronics onto the array, the ultimate goal being wearable, and cordless arrays. This places severe constraints on the maximum feasible power consumption per channel. We explore low power front-end topologies employing passive mixers. If combined with low-power high resolution successive approximation ADCs or continuous time sigma delta ADCs, receive arrays at only 100mW per channel may be feasible. 2692 Wireless Clock Transfer for MRI Phase Correction Jonathan Lu, Pascal Stang, Fraser Robb, John Pauly, Greig Scott One step in making wireless MRI possible is to sync the clocks at both the transmit side hardware that plays out the pulse, and the receive chain that processes the FID data. A discrepancy between the timing of the two clocks will lead to jitter that amounts to artifacts in the MRI image. In this work, we demonstrate a method to transfer a wireless clock without creating jitter artifacts in an MRI image. 2693 A chronic in situ coil system adapted for intracerebral stimulation during MRI in rats Dan Madularu, Chathura Kumaragamage, Axel Mathieu, Praveen Kulkarni, M. Rajah, Alain Gratton, Jamie Near We describe the fabrication and performance of a chronic in situ coil system designed to allow focal brain stimulation in awake rats while acquiring highly resolved MRI data. We developed a subcutaneously implantable receive-only surface radiofrequency coil to be fitted immediately adjacent to the rat skull surface during the cannulation procedure. SNR performance of the coil was superior to three commercially-available coils, in some instances by a factor of three. Widespread BOLD was observed in response to bicuculline and morphine microinfusions. This approach enables mapping the functional response to highly targeted stimuli such as microinfusions or optogenetics. 2694 High Power TRASE PIN Diode Control System Eric Der, Vyacheslav Volotovskyy, Boguslaw Tomanek, Jonathan Sharp TRASE is a k-space encoding method for low cost MRI that replaces conventional imaging gradients with a switchable RF transmit array. TRASE echo train sequences require rapid switching between transmit elements to cycle through up to six different phase gradient encoding fields. In vivo image resolution is currently limited because long (~500μs) refocusing pulses render the echo train sequence vulnerable to T2 losses. Here we present a design for a high power PIN diode driver circuit capable of robust and rapid switching of short (~100μs) high power pulses for a 24cm coil. Results from 0.2T experiments are shown. 2695 The effect of Gaussian Filtering in ZTE based Attenuation Correction of PET/MR J.M. Sousa, Håkan Ahlström, Mathias Engström, Mark Lubberink Zero-Echo Time (ZTE) has been proposed as an alternative attenuation method for PET-MR brain imaging. However, the filtering effects on these ZTE AC maps have not been explicitly discussed, in relation to effects on reconstructed and corrected images, and that is what we aim to develop in this study. 2696 A Simple Head-sized Phantom for Realistic System Characterization at 7T Wyger Brink, Zhiyi Wu, Andrew Webb A simple head-sized phantom has been developed to produce realistic B1 and B0 features and electrical loading conditions, as a tool for the evaluation of MR techniques and RF validation in high field MR systems. 2697 Enhancement of signal intensity using a wireless coil for FT-EPR oximetry study, implanted in an animal body Ayano Enomoto, Gadisetti Chandramouli, Alan Koretsky, Chunqi Qian, Murali Cherukuri, Nallathamby Devasahayam Improvement in sensitivity is required to detect the weak signals with Fourier transform Electron Paramagnetic Resonance (FT-EPR). In the proposed method, the signal from a wireless coil filled with sample was enhanced by using pumping coil in the regular EPR system. In this study, we achieved approximately 6-fold of improvement in signal intensity compared with conventional FT-EPR system under the simulated condition of animal body. We will also show the results of oximetry using the LiPc in, in vivo applications to measure tissue oxygenation.

Hybrid & Novel Technology
Engineering

Wednesday, 26 April 2017
 Exhibition Hall 16:15 - 18:15