27th ISMRM Annual Meeting • 11-16 May 2019 • Montréal, QC, Canada

Digital Poster Session
Engineering

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Monday, 13 May 2019
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Engineering Safety, Applications & Computation
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Engineering

Monday, 13 May 2019
 Exhibition Hall 09:15 - 10:15

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B0 Field Management & Shimming
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Engineering

Monday, 13 May 2019
 Exhibition Hall 09:15 - 10:15

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RF Coils & Arrays
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Engineering

Monday, 13 May 2019
 Exhibition Hall 09:15 - 10:15

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RF: Other
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Engineering

Monday, 13 May 2019
 Exhibition Hall 09:15 - 10:15

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MRI Unplugged: Wireless, Portable & Flexible
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Engineering

Monday, 13 May 2019
 Exhibition Hall 09:15 - 10:15

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Dielectrics, Decoupling, Switching & Control
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Engineering

Monday, 13 May 2019
 Exhibition Hall 09:15 - 10:15

 Computer # 1559. 126 A PIN-diode-driver for fast coil tuning using low detune currents Michael Eder, Andreas Horneff, Erich Hell, Johannes Ulrici, Volker Rasche To operate ultra short echo time (UTE) or zero echo time (ZTE) imaging, the ability to switch rapidly from detuned to tuned state is mandatory, as any delay causes signal loss for UTE or missing data points in the k-space center for ZTE. While propagation delays arising during radio frequency (RF) front end control can be measured and compensated, the dead time of the receive coil remains a limiting factor. In this contribution we investigated an approach to speed up PIN-diode based coil-tuning, using a dedicated driver providing a low detune current. Tuning times below 1000ns$1000\phantom{\rule{thinmathspace}{0ex}}\mathrm{n}\mathrm{s}$ could be realized. 1560. 127 UTE and ZTE on an unmodified clinical whole-body MR system using an RF signal acquisition system operating in parallel achieving an acquisition delay of less then 2µs$2\phantom{\rule{thinmathspace}{0ex}}\text{µ}\mathrm{s}$ Michael Eder, Andreas Horneff, Jan Paul, Alexander Storm, Erich Hell, Johannes Ulrici, Volker Rasche Ultra short echo time and zero echo time imaging on clinical systems are, even on modern systems, still limited by the rather long transient time required for switching from transmit to receive mode. In this contribution a complete receive-only chain was interfaced to an unmodified clinical whole-body MR system. Synchronization is achieved by a single trigger line as temporal reference and a time base signal, thus ensuring minimal interference and phase synchronous operation in parallel to the clinical system. An acquisition delay, between the real end of the excitation pulse and the beginning of signal acquisition, below 2µs$2\phantom{\rule{thinmathspace}{0ex}}\text{µ}\mathrm{s}$ could be realized. 1561. 128 Necessity for detuning large volume coils? Ria Forner, Martijn Lunenburg, Quincy van Houtum, Ladislav Valkovic, Jane Ellis, Christopher Rodgers, Dennis Klomp Implementing diode detuning on transmit coils is complicated and leads to a loss in efficiency on the transmit side. It has been common practice to include it nevertheless with the aim of preventing loss of receive efficiency and noise correlation between receiver through coupling via the body coil. However, nowadays, receiver coil elements are orders of magnitude smaller so flux linkage is intrinsically low. Moreover, the operating frequency is high to maintain strong tissue-loading, and finally preamplifier decoupling is applied to reduce the effects of mutual coupling. Here we show the coupling to receiver arrays for three non-detuned body coils. 1562. 129 Traveling-Wave Excitation for Electron Paramagnetic Resonance Imaging Bahareh Behzadnezhad, Nader Behdad, Alan McMillan One primary factor limiting the extension of electron paramagnetic resonance imaging (EPRI) beyond small animal applications is the challenge of create uniform RF fields at the higher RF frequencies needed to achieve the desired sensitivity. In this abstract, we discuss the development of a traveling-wave spectrometer operating in continuous-wave mode at 115 MHz. The spectrometer uses a parallel-plate waveguide supporting transverse electromagnetic waves to create a uniform transmit field and uses a conventional receive coil. We demonstrate the feasibility of a traveling wave system and its potential to be developed into an EPR imaging system. 1563. 130 A switch matrix to enable passive cloaking of a metasurface resonator for MRI applications Shimul Saha, Roberto Pricci, Maria Koutsoupidou, Ditjoni Katana, Srinivas Rana, Helena Cano-Garcia, Panagiotis Kosmas, George Palikaras, Efthymios Kallos We present a switch matrix for automatic tuning and detuning of a metasurface-resonator employed to enhance MRI scanning performance. A digital circuit with an inductor was used to pick up the magnetic field and generate a clock for switching which does not require any wire connection to the MRI scanner. The clock was used to activate an array of MOSFET switches, each of them connected to an adjacent pair of parallel wires of the resonator. The circuit was tested using a solenoid and the metasurface  resonance frequency was successfully tuned and detuned (cloaked) when the magnetic field was off-on respectively. 1564. 131 Effects of Parallel Imaging Acceleration on SNR Improvement with a High-Permittivity Helmet Shaped Former at Different Field Strengths Giuseppe Carluccio, Bei Zhang, Riccardo Lattanzi, Gregor Adriany, Kamil Ugurbil, Christopher Collins Use of high-permittivity materials has recently shown very promising results in terms of reduction of B1 inhomogeneities and increase of SNR. In particular, significant SNR increases have been predicted for a  high-permittivity helmet former within a close fitting head array. With this solution, for a 7T MRI system, an average SNR increase approaching 50% was obtained in the brain with SNR peak improvements of more than 200%. Until now, however, the effects of the high-permittivity helmet on g-factor and parallel imaging have not been examined. In this work, for three different acceleration rates we evaluate the impact of gfactor when a high-permittivity helmet shaped former is used in two different head arrays at two different field strengths. 1565. 132 The miniaturisation and simplification of a crossbar switch matrix system using stacked switch blocks Yunkyoung Ko, Chang-Hoon Choi, N. Shah, Jörg Felder The crossbar-type matrix creates open-stubs of varying length, depending on the switch configuration, which potentially degrades the MR image quality. However, this issue can be overcome efficiently with the use of a compensation circuit. But as the number of receive coils increases, a larger number of RF switches is required. In this study, we propose a miniaturised crossbar switch matrix which employs two independent, stacked boards. 1566. 133 On the Relationship Between Field Strength and Permittivity for Desired Effects of High-Permittivity Materials in MRI Christopher Collins, Giuseppe Carluccio, Bei Zhang, Gregor Adriany, Kamil Ugurbil, Riccardo Lattanzi Experience and general understanding dictate that greater relative permittivity is required to produce a similar effect at lower B0 field strengths and B1 frequencies. Here we use some fundamental explanations and preliminary numerical results for improving receive array performance at different field strengths to propose, more specifically, that permittivity should increase approximately with the inverse of the square of the field strength for an expected effect. 1567. 134 MEMS-based Ratio Adjustable Power Splitters for in-bore Switching of Transmit Array Compression Networks Charlotte Sappo, Gabriela Gallego, Xinqiang Yan, William Grissom A large number of coils in parallel transmission enables higher excitation accuracy with lower SAR, but the high cost and siting challenges associated with transmit amplifiers and their cabling has limited the number of channels to 8 on most 7T scanners. Array compressed parallel transmission overcomes this limitation using hardware networks that enable a large number of coils to be optimally driven by a small number of channels. These networks comprise ratio adjustable power splitter (RAPS) circuits that use hybrid couplers with reflection capacitors to apply relative phase shifts between signal branches that can be tuned to set the power ratios of the coil outputs. Here we describe and evaluate a MEMS-RAPS circuit that uses MEMS switches to switch between terminator capacitors, allowing dynamic remote tuning of output power ratios for more flexible transmit array compression networks. 1568. 135 Effect of high dielectric constant material configurations on the transmission field of an 8-channel dipole array at 10.5 T (447 MHz) Navid PourramzanGandji, Sebastian Rupprecht, Michael Lanagan, Bei Zhang, Riccardo Lattanzi, Russell Lagore, Jerahmie Radder, Gregor Adriany, Kamil Ugurbil, Qing Yang We used numerical simulations to investigate the effect of high dielectric constant materials (HDCM) on the performance of a transmit array with 8 dipole antennas for 10.5 T head MRI. Several parameters, including B1+ transmit efficiency, coupling between each array elements, and Specific Absorption Rate (SAR), were evaluated in the presence of HDCM with various relative permittivity values. We show that employing HDCM can decrease the coupling between each adjacent element by 16%, increase B1+ efficiency by more than 30% and lower total SAR by 40%. 1569. 136 Quality assurance of 8-channel transmit/receive switches for a 32-channel transmit/receive system at 7T UHF MRI Stefan Rietsch, Maximilian Voelker, Stephan Orzada, Daniel Leinweber, Mark Ladd, Harald Quick With increasing number of transmit and receive channels it becomes more and more important to monitor the behavior of the RF chain over time since weaknesses of custom-built hardware need to be known to the investigator. In this work, a quality assurance procedure for four identical 8-channel transmit/receive switchboxes for a 32-channel transmit/receive MR system at 7T is presented. In repeated measurements of a homogeneous phantom with an 8-channel transmit/receive coil, metrics like flip angle distribution, SNR and noise correlation are used to automatically assess quantitatively if significant changes of the hardware did occur. 1570. 137 Bilateral Breast coil for Fast Field-Cycling Relaxometric MRI Gareth Davies, Lionel Broche, Tanja Gagliardi, David Lurie, P. Ross Our research group is investigating the use of Fast Field-Cycling MRI (FFC-MRI) for clinical applications. Recent results have confirmed the presence of interesting FFC-MRI biomarkers in breast cancer that could lead to important applications. To study this we are developing an FFC-MRI compatible breast coil for use on patients. This work is presented here and shows excellent results, paving the way to clinical applications. 1571. 138 Control synchronization of power supplies and gradient amplifiers for better utilization of energy storage in MRI scanner Yash-Veer Singh, Juan Sabate, Ruxi Wang, Viswanathan Kanakasabai, Krishna Mainali, Huan Hu The magnetic resonance imaging (MRI) gradient driver is a high-performance inverter that provides large peak currents, >1000A, for the gradient magnetic fields used for imaging. MR system has capacitors for energy storage at the amplifier stage input voltages. Volume/weight reduction in energy storage elements is one of the challenging issue in design of compact and efficient MRI gradient system. It is possible to reduce capacitance value in energy storage elements by synchronizing the control of the gradient driver different subsystems. Control synchronization is achieved by providing reference value of coil current simultaneously to the different controller of the MRI system. 1572. 139 A three-element triple-tuned array implemented with switchable matching and tuning Travis Carrell, Romina Del Bosque, Matthew Wilcox, Mary McDougall This work describes a geometrically decoupled three-element array triple-tuned for 1H, 13C, and 31P at 3T implemented with switchable matching and tuning using PIN diodes. These particular nuclei were chosen to demonstrate the frequency range of the method, but the approach is extendable to any nuclei of interest.   Although the Q of the coils was degraded by the switching network, the use of PIN diodes enabled straightforward tuning and development. 1573. 140 On the minimum phase control required for B1 shimming Steven Wright Phase only B1 shimming is a cost-effective and simple approach to improving RF field homogeneity for high field MRI.  Without a multiple channel transmitter,  this is implemented by switching transmission lines or possibly lumped element phase shift networks.   This abstract investigates the minimum phase shift required in a potential multi-bit electronic phase shifter.  For practical shimming solutions, those not requiring significant increases in power to achieve a 90 degree tip angle as compared to ‘birdcage’ or conjugate phase currents, it is concluded that 45 degrees may be a sufficient resolution for such a phase shifter. 1574. 141 Digitally Controlled High-Power Phase Shifter for B1 Shimming at 7T Chenhao Sun, Neal Hollingsworth, Kevin Patel, Kasra Ghadiri, Chung-Huan Huang, Steven Wright To mitigate electromagnetic wave interference in high field MRI, RF shimming relies on the ability to manipulate the phase and amplitude of the Tx signal on each channel. The simplest approach is to change phase shifts by switching transmission lines. We propose an electronically controlled phase shifter providing eight different states of phase shifting (0°, 22.5°…...135°, 157.5°), designed to handle 1kW Tx power and is non-magnetic so that it can be used in the magnet room. Measurement demonstrate an average insertion loss of -0.94dB and an average phase error -1.35° compared with design values. 1575. 142 Receiver ring-down attenuation for Ultra-Low field MR Ruben Pellicer-Guridi, Michael Vogel, Rainer Körber, Jan-Hendrik Storm, Jiasheng Su, David Reutens, Viktor Vegh Ultra-low field MR detector coils experience long dead-times which reduce acquisition efficiency. We present a simple low insertion loss Q-damping scheme and a post-processing method that, combined, allow earlier signal acquisition. Proposed methods have been empirically verified with a cylindrical detector at 2.5 kHz. This approach can improve imaging efficiency for ULF MR considerably, promoting the use of inexpensive resistive coils for low-cost, portable ULF MR instruments. 1576. 143 Self-decoupled coils for MRI receiver arrays based in an external resonator Rafael Baron, Juan Sanchez-Heredia, Vitaliy Zhurbenko, Jan Ardenkjær-Larsen A method of decoupling coils by the use of an external resonator has been developed. The method provides several advantages as a decoupling strategy which does not strongly depend on the input impedance of the amplifier, can use flexible wires and provide a low dependence of the coupling to the position of one coil relative to the other. The concept was initially developed for cryogenic coils due to its simple implementation but is presented to room temperature Copper-based receivers. 1577. 144 Massively Accelerated Simulations of High-Permittivity Materials in Multi-Channel Receive Arrays Wyger Brink, Jeroen van Gemert, Peter Börnert, Rob Remis, Andrew Webb High-permittivity materials are known to offer potential increases in the sensitivity of RF coils, increasing SNR or reducing SAR. Design guidelines are not straightforward, however, in part due to complex coil interactions. We here present a numerical method for the rapid (e.g. ~1 sec) assessment of dielectric materials positioned in a 3T torso receive array, enabling full exploitation of this technology. 1578. 145 Water-tunable Spiral Metamaterial Resonator for Radiofrequency Field Enhancement for Receive Coils at 1.5T Elizaveta Motovilova, Srikumar Sandeep, Michinao Hashimoto, Shao Ying Huang We present a low-profile tunable spiral metamaterial resonator for radio-frequency field enhancement and penetration increase for receive coils at 1.5T MRI. The resonator consists of a dielectric substrate with a cavity for water deposition and two conducting spirals placed on each side of the substrate. The proposed structure is placed between a receive loop-coil and a load. The resonance frequency of the coil-spiral system can be varied within a range of 15MHz by changing the water volume in the cavity from 0ml to 12ml. The system shows a magnetic field refocusing and enhancement with a considerable increase in penetration depth. 1579. 146 Shunt, don't block: A New Approach to Dual Nuclear Coil Design. Matthew Erickson Development of dual nuclear coils with high efficiency on both 1H and X remains a challenge.  The advent of hyperpolarized 13C imaging and hyperpolarized rare gas imaging has provided impetus for developing such a coil.  In this work, we report prototype 1H/13C surface coil that makes use of tune/match circuits augmented by high performance shunt notch filters constructed from hybrid transmission line circuits.  In this design, all conductive elements in the utility region are simultaneously resonant with high efficiency on both 1H and X.  The design may be extended to both volume and array coils for most 1H/X pairs. 1580. 147 A triple tuned coil and front-end for simultaneous multinuclear MR imaging and spectroscopy Chung-Huan Huang, Hongli Dong, Stephen Ogier, Chenhao Sun, Steven Wright There are several ways to implement simultaneous acquisition for multiple nuclei. A single-port triple tuned coil is the simplest structure and has the best potential for integration into multiband arrays. This abstract demonstrates an approach to acquire three nuclei (1H/23Na/2H) MRS simultaneously by using a home-built broadband spectrometer with a triple tuned coil. The broadband spectrometer front-end is capable of providing separate gains to each of studied nucleus where signal sensitivity variation is large and can reduce data throughput load by using undersampling techniques while still maintaining similar performance as a Varian Inova system. 1581. 148 Interactive hand gestures for HoloLens rendering control of real-time MR images Andrew Dupuis, Dominique Franson, Nicole Seiberlich, Mark Griswold User interactions via hand gestures are added to a real-time data acquisition, image reconstruction, and mixed-reality display system to allow a user to interact more flexibly with the rendering. Images at precalibrated slice locations are acquired and displayed in real-time to the user, who is able to toggle between viewing some or many slices as well rotate, resize, and dynamically adjust the window and level of the rendering. 1582. 149 Dynamic Dual Frequency Transmit and Receive Coil Pair for Development of a New Open MRI System Charles Rogers III, Gigi Galiana, Todd Constable We present progress on development and testing of a two-coil array with each coil separately and dynamically tunable between dual frequencies.  This test setup works toward the goal of developing a larger nine-element coil array for a new style of open MRI system utilizing the Bloch-Siegert shift at low Bo field. The array design is such that pairs of coils are selected for transmission at ~850kHz while allowing simultaneous receive at ~1MHz on the non transmitting coils.  We discuss the construction and present measurements of RF scattering parameters of a two-coil test setup. 1583. 150 A highly-miniaturized inverted cable trap Xinqiang Yan, John Gore Cable traps are commonly used for RF coils to suppress the common-mode current flowing on the outer conductor of coaxial cables. In massive-element array coils, conventional cable traps become cumbersome and not easy to assemble due to the limited space. In this work, we propose a novel circuit component called an “inverted cable trap”, which uses the outer conductor of a coaxial cable to form a capacitor rather than an inductor and which can be highly miniaturized. This inverted trap suppresses common-mode signals by up to -23 dB at 300 MHz which makes it valuable for operations at 7T.
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MR System, Characterization & Tuneup
Digital Poster
Engineering

Monday, 13 May 2019
 Exhibition Hall 09:15 - 10:15