ISMRM & SMRT Virtual Conference • 08-14 August 2020

Digital Poster Session

Engineering: RF Coils

Note: There are no live presentations or sessions associated with these posters.

Digital Posters

Session Topic: RF coils
Session Sub-Topic: RF Coils 1
Digital Poster
Engineering

 4018 A tight-fit flexible high-impedance coil array for high-resolution imaging of small ex-vivo specimen using a human 7T scanner Koji Fujimoto1, Bei Zhang2, Shin-ichi Urayama1, Atsushi Shima3, Nobukatsu Sawamoto4, Ryosuke Takahashi3, Tomohisa Okada1, and Martijn A. Cloos2 1Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan, 2Center for Advanced Imaging Innovation and Research (CAI2R) and Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, 3Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto University, Kyoto, Japan, 4Department of Human Health Sciences, Kyoto University Graduate School of Medicine, Kyoto University, Kyoto, Japan By borrowing concepts from the high-impedance glove coil, we propose an “elastic-tube coil” for imaging ex-vivo specimen at 7 Tesla. The elasticity of the sock makes it easy to setup and ensures a minimal distance between the coils and the specimen. Two high-impedance elements were stitched to an elastic tube suspended in a custom 3D printed housing. Volumetric gradient echo images of an ex-vivo human brain specimen were acquired with 60um-isotropic resolution. 4019 A Novel Clinical Friendly 7T T/R 32-Channel Head Coil Using Skipped-Rung Birdcage as Transmitter Tsinghua Zheng1, Xiaoyu Yang1, Blaise Whitesell1, Martin Domondon1, Paul Taylor1, Samuel Musilli1, and Labros Petropoulos1 1Quality Electrodynamics, LLC, Mayfield Village, OH, United States We propose a novel skipped-rung birdcage coil as the local transmitter for head imaging at 7 Tesla. This concept allows sizable openings on the coil anterior. The openings improve both patient comfort and workflow. A 7T head coil using the skipped-rung birdcage transmitter and a 32-channel receiver array was constructed and evaluated. The preliminary test results show a good transmitting efficiency and a good image quality compared with a commercial 7T head coil. 4020 Human colon imaging: simulation of novel SwiM RE-coils Hamza Raki1,2, Kevin Tse Ve Koon1, Henri Souchay2, Simon A Lambert1, Fraser Robb3, and Olivier Beuf1 1Univ Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1206, F-69100, Lyon, France, 2GE Healthcare, Buc, France, 3GE Healthcare, Aurora, OH, United States Coil-loop geometries were defined and simulated on electromagnetic (EM) software FEKO. Image intensity distribution was evaluated for different orientations with respect to B0. Overall, single loop and double loop with opposite current show complementary results. The switch between these two loops could be realized using MEMS (Micro Electro-Mechanical System) switches. This can reduce the dependency of the coil-sensitivity to its orientation with respect to B0 and can lead to the development of SwiM RE-coils (SWItches MEMS for Reconfigurable Endoluminal coils). 4021 A Mono-surface 8Tx/16Rx Antisymmetric Dipole Antenna Array for Parallel Transmit Cardiac MRI in Pigs at 7T Ibrahim A. Elabyad1, M. Terekhov1, and Laura M. Schreiber1 1Chair of Cellular and Molecular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Wuerzburg, Wuerzburg, Germany A mono-surface 8Tx/16Rx antisymmetric dipole antenna array was designed and tested for parallel transmit (pTx) cardiac magnetic resonance imaging (cMRI) in pigs at 7T. The antisymmetric array comprised of a mono-surface 16-dipoles arranged so that two central L-shaped dipoles were anti-symmetrically flanked by 7-dipoles on either side. Combined FA, SNR, and g-factor maps were acquired in phantom using the dipole antenna array and compared with an 8Tx/16Rx loop array. After $$B_1^+$$$-shimming using the dipole array, the SNR was enhanced by ~20% and FA by ~42%. Dipole antenna array has demonstrated ~20-times improvement in RSD of the FA after $$B_1^+$$$-shimming. 4022 Development and RF Shimming of an 8Tx/16Rx Antisymmetric Transceiver Coil Array for Parallel Transmit Cardiac MRI in Humans at 7T Ibrahim A. Elabyad1, M. Terekhov1, and Laura M. Schreiber1 1Chair of Cellular and Molecular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Wuerzburg, Wuerzburg, Germany To develop and optimize an 8Tx/16Rx antisymmetric transceiver coil array with improved characteristic for static phase $$B_1^+$$$-shimming and parallel receive for human cardiac MRI at 7T. The array design was based on antisymmetric loop configurations in 2-different directions (L/R and A/P). EM-simulations were carried out in phantom and 4-human models (Duke, Ella, Gustav, and Laura). $$B_1^+$$$-shimming has been carried out for 16-elements with three different cost functions to improve $$B_1^+$$$-field homogeneity, $$Tx_{eff}$$$ and weighted combination of both within Duke and Ella models. The hardware and imaging performance of the antisymmetric array was validated through EM-simulations and phantom MR-measurements at 7T. 4023 Dipole Decoupling with Parasites Gregor F. Neumann1,2, Mark E. Ladd1,2, and Arthur W. Magill1 1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Physics & Astronomy, Heidelberg University, Heidelberg, Germany We investigate the decoupling of a pair of fractionated dipoles using an additional passive parasitic dipole. Decoupling is optimised either geometrically, by adjusting the parasite length and standoff distance from the active dipoles, or by adding resistance and reactance to the parasite centre. Adjusting two parameters allows control over the amplitude and phase of the decoupling signal induced via the parasite, producing very strong decoupling at the target frequency (better than -40 dB). The effect is demonstrated using EM simulation and verified with bench measurements. 4024 A 30-Channel Single Layer Transceiver Head Coil at 3.0T Haoqin Zhu1, Xiaoyu Yang1, Michael Wyban1, Yiping Guan2, and Yoshinori Hamamura2 1Quality Electrodynamics, LLC (QED), Mayfield Village, OH, United States, 2Canon Medical Research USA, Inc, Mayfield Village, OH, United States A novel open design 30ch transceiver head coil without using a local RF power source is proposed. Each coil element has no detuning circuit, couples to the system whole body coil inductively, and generates a uniform B1+ field in transmit mode. The same coil element also acts as a typical phased array element in receive mode. The transceiver feature of the coil may benefit the SAR demanding simultaneous multi-slice (SMS)/multi-band (MB) and high-resolution imaging and still keep the clinical friendly openings. In addition, the same coil element approach simplifies the coil circuit and improves the signal-to-noise ratio (SNR). 4025 A Novel Ultra-Flexible High-Resolution AIR (Adaptive imaging receive) 64-Channel Bilateral Phased Array for 3T Brachial Plexus MRI Yun-Jeong Stickle1, Clyve Follante1, Mark Giancola1, David Anderson1, Fraser Robb1, Victor Taracila1, Robert Stormont2, Holly Blahnik3, Simone Winkler4, and Darryl Sneag5 1MR Engineering, GE Healthcare Coils, Aurora, OH, United States, 2MR Engineering, GE Healthcare, Waukesha, WI, United States, 3MR Apps&WF, GE Healthcare, Waukesh, WI, United States, 4MRI Engineering, Weill Cornell Medicine, New York, NY, United States, 5Radiology and Imaging, Hospital for Special Surgery, New York, NY, United States An ultra-flexible AIR 64-Channel bilateral phased array coil is described for acquiring high-sensitivity images of the brachial plexus by wrapping coil elements snugly around the cervical, shoulder, axillary, and arm regions. This coil comprises a foam posterior and flexible flaps with a low loss malleable conductor optimized for zero reactance. An exceptionally low noise preamplifier is tolerant of a wide range of loading. This coil facilitates imaging large fields of view bilateral brachial plexi, as well as higher resolution unilateral imaging for detailed evaluation of nerve fascicular architecture and other pathology, thereby optimizing setup time and patient comfort. 4026 Developing High Channel Count Receive Arrays for Human Brain Imaging at 10.5T Nader Tavaf1,2, Russell L. Lagore1, Steve Jungst1, Shajan Gunamony3, Jerahmie Radder1, Andrea Grant1, Edward Auerbach1, Steen Moeller1, Kamil Ugurbil1, Gregor Adriany1, and Pierre-Francois Van de Moortele1 1Center for Magnetic Resonance Research (CMRR), University of Minnesota Twin Cities, Minneapolis, MN, United States, 2Department of Biomedical Engineering, University of Minnesota Twin Cities, Minneapolis, MN, United States, 3Centre for Cognitive Neuroimaging, University of Glasgow, Glasgow, Scotland Highly decorrelated, high channel count receive arrays are a prerequisite to capturing the signal-to-noise ratio and acceleration performance potential of ultra-high field MRI. A self-decoupled 32-channel receive array was built for human brain imaging at 10.5T. Noise correlation and signal-to-noise ratio (SNR) of the RF coil were measured in phantom experiments at 10.5T. SNR was compared to a commercial 32-channel receiver array at 7T. Noise correlation matrices demonstrated effective decoupling of receive elements. Experimental SNR measurements demonstrated on average 60% higher overall SNR at 10.5T compared to 7T. 4027 A 4-Channel Conformal Hybrid Coil Array for Rat Limb Imaging at 7T Jan Paska1,2, Amparo Ruiz1,2, and Jose Raya1,2 1Center for Advanced Imaging Innovation and Research (CAI2R), NYU School of Medicine, New York, NY, United States, 2Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, NY, United States We aim to image the rat limb in longitudinal follow up studies using contrast agents at 7T. Consistent positioning and a high and uniform SNR is required over the ROI. Commercial surface coil arrays offer a high SNR close to the surface but are difficult to position and have poor penetration. Therefore we decided to design a dedicated coil array taking into account the animal's anatomy. We optimized the design in simulations, compared it to a commercial surface coil array in a phantom, and show first in-vivo images. 4028 Multilayer Radiofrequency Coils: A Novel Surface Coil Design for Improved B1+ Efficiency and Signal-to-Noise Tony Zhou1,2, Justin YC Lau1,2, Jack JJJ Miller1,2,3, Navjeet Chhina4, Christopher Randell4, and Damian J Tyler1,2 1Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom, 2Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, United Kingdom, 3Department of Physics, University of Oxford, Oxford, United Kingdom, 4PulseTeq LTD, Chobham, United Kingdom Surface transmitters are often B1+ limited for X-nuclear applications due to hardware limitations of broadband power amplifiers. For both X-nuclear MRI and proton MRI, improved signal detection is always desired. Commonly, signal is measured using surface radiofrequency loop coils or coil arrays. We propose a novel surface coil design using stacked copper layers from one continuous track for increased magnetic flux and sensitivity over a central region of the coil. ‘Multilayer’ designs promise increased B1+ efficiency and Signal-to-Noise, seen using electromagnetic simulations and verified experimentally when compared to conventional loop coils over a range of diameters. 4029 An Implantable MRI Micro-coil of Blood vessel for High Sensitivity and High SNR Imaging at high field MRI. Sana Ullah1 and Hyoungsuk Yoo1 1Department of Biomedical Engineering, Hanyang University, Seoul, Republic of Korea The importance of implantable micro-coil has been rapidly increased due to its advantages in diagnosing intravascular and brain diseases. In this study, the receive-only conformal-shaped micro-coil was designed and presented. Our research demonstrated that homogeneous B1- magnetic field distributions and receptive sensitivity around the blood-vessel walls were achieved by using the proposed micro-coil. 4030 An Inductive Coupling Neck Coil for Expanding Effective Coverage and Increasing SNR at 3.0T Guangqi Li1, Xinyuan Wang2, Zhi Zhao2, Wanshan Li2, Yishi Wang3, and Hua Guo1 1Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, 2Tsimaging Healthcare Ltd, Beijing, China, 3Philips Healthcare, Beijing, China The image uniformity and signal to noise (SNR) is not high enough for extra-cranial imaging with the existing Head-Neck coil due to the limited channel number of the neck section. Traditionally, minimizing the coupling between nearest-neighbor coils is necessary for eliminating signal crosstalk. However, in this work, we propose an inductive coupling coil design to increase effective coverage without any signal interference, thereby breaking through the limitation of the channel number. Extra-cranial imaging has better image uniformity and 16.5% higher SNR using the new neck coil at 3.0T. 4031 Development of a biplanar volume coil for an open 0.1 T MRI system Maksym Yushchenko1, Najat Salameh1, and Mathieu Sarracanie1,2 1Laboratory for Adaptable MRI Technology (AMT lab), Dpt of Biomedical Engineering, University of Basel, Allschwil, Switzerland, 2Medical Image Analysis Center (MIAC AG), Basel, Switzerland An open, biplanar volume RF coil was built and tested as a transceiver with a homogeneous B1 at 4.2 MHz. We demonstrate its feasibility and performance in a low-field, open biplanar magnet. While giving good sensitivity, this geometry provides easy access to the object from multiple sides. In addition to simpler positioning of patients, this potentially opens the way for improved MRI applications where access is primarily required such as interventional MRI. 4032 Flexible torso array coil for Fast Field-Cycling MRI at 8.5 MHz Robert S Stormont1,2, Broche M Lionel1, P. James Ross1, Gareth R. Davies1, and David J. Lurie1 1School of Medical Sciences, Aberdeen Biomedical Imaging Centre, University of Aberdeen, Aberdeen, United Kingdom, 2Magnetic Resonance Imaging, GE Healthcare, Waukesha, WI, United States An array coil for 0.2 T reception has been developed for colon and heart studies in a FFC-MRI system.  The array consists of 3 element posterior/anterior sections, with 16cm loops arranged in a “venn” pattern. Minimizing conductor losses and noise figure over varying loading is particularly important in a low field system.  A two-turn  litz arrangement was chosen offering good flexibility and Qu/Ql ratios. Interfacing electronics component topologies were simplified  losses keping losses to a minimum.  Matching, blocking, decoupling, and preamplification reside at element.  Packaging is flexible textiles and substrates. The resulting array conforms and retains performance with varying anatomy. 4033 RF endoluminal coils with NMR electro-optical conversion and transmission for colon wall imaging: Initial finding Paul Nobre1, Alice Ferrando1, Gwenaël Gaborit2,3, Raphaël Sablong1, and Olivier Beuf1 11Univ. Lyon, CREATIS ; CNRS UMR 5220 ; INSERM U1206 ; INSA-Lyon ; UJM-Saint Etienne ; Université Lyon1 ; 69616 Villeurbanne, France, Lyon, France, 2University of Savoie, IMEP-LAHC, UMR 5130, 73376 Le Bourget-du-Lac, France, Le Bourget-du-Lac, France, 3KAPTEOS, 73376 Sainte-Hélène-du-Lac, France, Sainte-Hélène-du-Lac, France Receive surface coils in MRI have proven to enable higher spatial or temporal resolution. However, the proximity of the galvanic connexions with the body when the coil is used as receiver coil together with a volume coil can lead to safety issues, in particular for inner coil. This configuration can induce currents in coaxial cable and local SAR increase can be induced. Replacing the galvanic connexions with optical ones could prevent those risks and enable safe colon wall imaging with endoluminal coils. First experimental demonstration of an electro-optic conversion based on Pockel’s effect is demonstrated at 4.7T.

Session Topic: RF coils
Session Sub-Topic: RF Coils 2
Digital Poster
Engineering

Session Topic: RF coils
Session Sub-Topic: RF Coils 3
Digital Poster
Engineering

 4048 Sensitivity Enhancement at 7T Brain MR imaging Using Wireless Coupled-Split-Ring-Resonators Array Akbar Alipour1, Gaurav Verma1, Michael Bush2, Judy Alper1, and Priti Balchandani1 1Biomedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, 2Siemens Medical Solutions USA, Inc, New York, NY, United States Image quality in the brain periphery at ultra high ﬁeld MRI is severely limited by low sensitivity. In this work we illustrate an efficient method for enhancing imaging sensitivity at 7T in a cadaver brain. The method is based on the application of a wireless coupled-split-ring-resonator array that amplifies the MR signal during acquisition, which can alleviate the low sensitivity problem in the brain periphery when low ﬂip angle and low SAR sequences are needed. Initial ex-vivo 7T MR brain imaging results showed that 2-fold to 6-fold SNR gain was obtained using this array. 4049 RF field extension and improvement by using floating strip conductors for parallel microstrip coil for PET/MRI insert Md Shahadat Hossain Akram1, Takayuki Obata2, and Taiga Yamaya1 1Advance Nuclear Medicine Sciences, National Institute of Radiological Sciences (NIRS-QST), Chiba, Japan, 2Molecular Imaging and Theranostics, National Institute of Radiological Sciences (NIRS-QST), Chiba, Japan For parallel transmit coils, maximum field-intensity is seen for the ROI close to each coil and, peripheral imaging region in between the coils usually show minimum field-intensity. For this reason, a compact orientation of multiple coils is usually used to surround the ROI. An approach of field extension to the regions in between coils is presented here for a 4-channel microstrip coil. Multiple narrow floating copper strips (width 4 mm) were used in between coils. For three such strips, image signal intensity between the coils almost doubled, that resulted in 20% increase in image homogeneity and 25% increase in SNR. 4050 The Very RF Hungry Caterpillar Trap (Highly Flexible, Distributed System of Toroid Cable Traps) Ekin Karasan1, Victor Taracila2, Fraser Robb2, and Michael Lustig1 1Department of Electrical Engineering, University of California, Berkeley, CA, United States, 2GE Healthcare, Coils, Aurora, OH, United States “In the light of the moon a little egg lays on a leaf”[7] Management of cabling connecting coil arrays to system remains the nightmare of RF-engineers. Coupling within arrays to cabling reduces performance, and coupling to transmit field causes high shield currents. Consequently, traps are placed on conductors. To provide high blocking, traps are rigid, large and often heavy, hindering flexibility. Instead of a few high blocking traps, we propose a distributed system of small, elastic traps.  We leverage self-shielded resonant toroids forming a caterpillar-like structure. We show that this design can attenuate shield currents while being robust to flexing. 4051 Design and evaluation of a dual-tuned circular dipole antenna up to 14T MRI Suk-Min Hong1, Chang-Hoon Choi1, Jörg Felder1, and N. Jon Shah1,2,3,4 1Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany, 2Institute of Neuroscience and Medicine 11, INM-11, JARA, Forschungszentrum Jülich, Jülich, Germany, 3JARA - BRAIN - Translational Medicine, Aachen, Germany, 4Department of Neurology, RWTH Aachen University, Aachen, Germany When the field strength of MRI is increased to 14T, the capacitor values required to tune a conventional loop coil become extremely small. For 7T MRI, the circular dipole antenna has been introduced and evaluated as the array structure and new decoupling method. In this study, we modified a circular dipole antenna to a dual-tuned circuit by using an LC trap. The coil operates as a circular dipole antenna for the proton signal as the trap blocks 1H current and operates as a conventional loop at the X-nuclei frequency. The dual-tuned circular dipole antenna was evaluated up to 14T frequency. 4052 A Patient-Friendly Coil For Bilateral Carotid Artery Imaging Bili Wang1, Justin Ho 1, Jerzy Walczyk1, Thanh D Nguyen2, Bei Zhang1, and Ryan Brown1 1Radiology, New York University Langone Health, New York, NY, United States, 2Radiology, Weill Cornell Medical College, New York, NY, United States Carotid MRI imaging can be vital in preventing heart disease and stroke but is difficult due to variable neck anatomy. Traditional rigid coils have a hard time achieving a close fit on all patients which can result in SNR loss that is essential for delineating the thin vessel wall. We designed and implemented an 8-channel flexible coil by incorporating the resonators into tailored cloth sleeves with integrated semi-rigid skeletons and a head cradle that provided the means for straightforward patient positioning and comfort, and a contoured fit for high SNR. 4053 A radiolucent 32-channel high impedance coil receive array to accelerate 3D imaging on hybrid 1.5 T MR-linac systems Stefan Emiel Zijlema1,2, Luca van Dijk1, Jan J.W. Lagendijk1, Dennis W.J. Klomp3, Catalina S. Arteaga de Castro4, Rob H.N. Tijssen1, and Cornelis A.T. van den Berg1,2 1Department of Radiotherapy, UMC Utrecht, Utrecht, Netherlands, 2Computational Imaging Group for MRI diagnostics and therapy, Centre for Image Sciences, UMC Utrecht, Utrecht, Netherlands, 3Department of Radiology, UMC Utrecht, Utrecht, Netherlands, 4Tesla Dynamic Coils, Zaltbommel, Netherlands High impedance coils (HICs) offer major advantages  for use during MRI-guided radiotherapy (MRIgRT), as they lack lumped elements that can attenuate radiation. Furthermore, their flexibility and low channel coupling simplify high-density array development and enable on-body placement. Here, we present a fully functional 32-channel HIC array, confirmed its radiation transparency (radiolucency) and compared the imaging performance with the current clinical (LIC-based) array.  Dosimetrically, no clinically significant attenuation was caused by the array. Imaging-wise, the prototype showed higher SNR values and lower g-factors, thus allowing for faster imaging.  In conclusion, our 32-channel array can accelerate all imaging for MRIgRT applications. 4054 Self-decoupled Folded Dipole Antenna Ming Lu1,2,3, John C. Gore1,2, and Xinqiang Yan1,2 1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, 2Department of Radiology, Vanderbilt University Medical Center, Nashville, TN, United States, 3College of nuclear equipment and nuclear engineering, Yantai University, Yantai, China In ultra-high-field MRI, both curl-free (dipole-like) and divergence-free current patterns (loop-like) are desired for better parallel transmission performance as well as to approach the ultimate receive performance for deep tissues. But decoupling dipole antennas is still a challenging topic. However, as shown in previous work, the strongest coupling in a dipole array is actually end-to-end between elements. Another challenge when using dipoles in dense arrays comes from their length, 45 cm at 300 MHz. We propose a novel, folded figure-of-eight (Fo8) configuration to shorten the dipole and simultaneously make it self-decoupled from others. 4055 Simulation of Focused RF Heating using a High-Channel-Count RF Array and a Maximum SAR Algorithm Koray Ertan1,2, Joshua De Bever1, Mihir Pendse1, Paolo Decuzzi2, and Brian Rutt1 1Department of Radiology, Stanford University, Stanford, CA, United States, 2Italian Institute of Technology, Genoa, Italy A 70-channel parallel transmit RF coil array intended for focused RF applications was designed and simulated at four frequencies (298 MHz, 447 MHz, 900 MHz and 1200 MHz) using a Ella body model. A previously proposed maxSAR algorithm was used to focus SAR in target regions while limiting the SAR in background tissues. Spatial maps of optimized SAR distribution are shown for several target locations and all frequencies. SAR distributions together with temperature and CEM43 maps suggest that clinical levels of focused hyperthermia can be achieved using high channel count parallel transmit RF coils and the maxSAR algorithm. 4056 Development and Evaluation of a pTx Transceiver Cardiac Array Based on Y-Shape Central 3-Loop Arrangement for Cardiac MRI in Pigs at 7T Ibrahim A. Elabyad1, M. Terekhov1, D. Lohr1, and Laura M. Schreiber1 1Chair of Cellular and Molecular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Wuerzburg, Wuerzburg, Germany An 8-element anterior array based on central 3-elements Y-shape arrangement was combined with a rectilinear 8-elements posterior array to form a dedicated 8Tx/16Rx pTx transceiver cardiac array for pigs was developed. The hardware and imaging performance of the pig array was validated through EM-simulations, phantom and ex-vivo MR-measurements at 7T. Combined SNR, FA, g-factor maps, and high-resolution ex-vivo cardiac images were acquired with an in-plane resolution of 0.3mm×0.3mm. A SNR of 36±23 was achieved within the heart of the pig. Parallel imaging with acceleration factor (R=4) was possible while keeping the mean g-factor within the heart region at 1.14. 4057 Endoluminal imaging with MEMS in series with loop coil for active decoupling Hamza Raki1,2, Kevin Tse Ve Koon1, Isabelle Saniour1, Henri Souchay2, Simon A Lambert1, Fraser Robb3, and Olivier Beuf1 1Univ Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1206, F-69100, Lyon, France, 2GE Healthcare, Buc, France, 3GE Healthcare, Aurora, OH, United States A Receiver-Endoluminal-Coil (REC) integrating an active-decoupling circuit based on MEMS switch in series with the loop (sMEMS) was built and characterized on bench and at 1.5T. The results were compared to a conventional PIN-diode REC. Although the quality factor of sMEMS was significantly lower (34%) than the one of PIN-diode, efficient (|S11|<-0.1dB) and fast (delays<8µs) active-decoupling were obtained for the sMEMS. Obtained MR images display no hyper intensity or artifacts due to active-decoupling failure. SNR-values and SNR-isocontours of sMEMS were similar to those of PIN-diode for GRE and lower for FSE sequences. sMEMS can bring new coil-design possibilities for endoluminal-imaging. 4058 Feasibility study of volume RF coils constructed using coupled H-shaped dipole antennas for MR imaging at ultrahigh fields Shasha Yue1, Zhe Wang1, Cheng Fang1, Nan Li2, Yan Hou1, Kun Zhang1, Rong Xue3,4,5, Ye Li2,6, and Xiaoliang Zhang7 1Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, 2Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, 3State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, 4University of Chinese Academy of Sciences, Beijing, China, 5Beijing Institute for Brain Disorders, Beijing, China, 6Shenzhen Key Laboratory for MRI, Shenzhen, China, 7Department of Biomedical Engineering, State University of New York, Buffalo, NY, United States, Buffalo, NY, United States The feasibility of constructing the non-array volume RF coil using the coupled dipole antennas has been explored. The electromagnetic coupling among the dipoles is relatively weak and not readily to form a volume coil unless massive and dense dipoles are employed. An H-shaped dipole is proposed as the basic resonant elements to construct the ultrahigh field volume RF coil. The simulation and imaging experiment results show that the proposed H-shaped dipoles can achieve sufficient electromagnetic coupling with a much-reduced number of dipoles and form a volume coil with a practical coil length and uniform B1 fields in an efficient way. 4059 A flexible five-channel shielded-coaxial-cable transceive neck coil for high resolution carotid imaging at 7T Irena Zivkovic1, Thomas Ruytenberg1, and Andrew Webb1 1Radiology Department, Leiden University Medical Center, Leiden, Netherlands Imaging the carotid arteries at 7T requires a multichannel array which allows B1-shimming and conforms to different neck sizes. The major challenge is to minimise coupling between closely-spaced coils and to make the coupling relatively insensitive to loading conditions. We have designed a five channel transceive array composed of  shielded-coaxial-cable coils placed on the anterior part of the neck and conforming to the anatomy. Coil flexibility has been demonstrated by imaging subjects with different neck circumferences.  In vivo black-blood  images were acquired with very high in-plane spatial resolution (0.25 x 0.25 mm2) with clear depiction of the vessel walls. 4060 An automatic tuning free pin diode shunt switch with artificial non-uniform transmission line λ/4 sections for receive only surface array coils. Miheer Pradeep Mayekar1, Rohit Apurva1, Bhaskara Naik1, and Rajesh Harsh1 1Technology Innovation Department, Society for Applied Microwave Electronics Engineering and Research, Mumbai, India The excessive high-power during transmission saturates or in worst case damages the preamplifier. In shunt switch an artificial (lumped component) uniform λ/4 section is inserted between two shunt diodes to increase its isolation. To restore the preamplifier-decoupling performance degraded by λ/4 section, it is required to add lossy tuning components e.g. varactor diodes to change the λ/4 section’s phase. We are proposing a pin-diode shunt RF switch with two lumped component non-uniform λ/4 sections which will maintain the preamplifier decoupling performance during reception sans complex tuning components and provides additional isolation of around 10-db as compared to uniform λ/4 sections. 4061 A Dedicated 17O Rx Array to Assess Renal Metabolism of Donor Kidneys Ali Caglar Özen1,2, Johannes Fischer1, Hao Song1, Yanis Taege1, Christian Schuch3, Rianne Schutter4, Cyril Moers4, Ronald JH Borra5, and Michael Bock1 1Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, 2German Consortium for Translational Cancer Research Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany, 3NUKEM Isotopes GmbH, Alzenau, Germany, 4Department of Surgery – Organ Donation and Transplantation, University Medical Center Groningen, Groningen, Netherlands, 5Medical Imaging Center, University Medical Center Groningen, Groningen, Netherlands Direct 17O-MRI can be used to measure renal metabolism in perfused kidneys in an organ transplantation setup. To optimize SNR, a dedicated 17O Rx array was designed that fits into a perfusion box used for functional metabolism tests of the donor kidneys. The increased filling ratio resulted in higher SNR compared to the volume and surface Tx/Rx coils. In combination with a 17O birdcage Tx coil for homogeneous excitation the 4-element Rx array could also be used for parallel imaging. 4062 UHF MRI at 14 T: Initial transmit performance analysis of 8-channel local RF arrays using fractionated dipoles Marco L. Wittrich1, Andreas K. Bitz1,2, Jonathan K. Stelter1, Mark E. Ladd1,3,4, and Thomas M. Fiedler1 1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Electromagnetic Theory and Applied Mathematics, Faculty of Electrical Engineering and Information Technology, FH Aachen – University of Applied Sciences, Aachen, Germany, 3Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany, 4Faculty of Physics and Astronomy and Faculty of Medicine, University of Heidelberg, Heidelberg, Germany Numerical simulations were used to design and evaluate antenna arrays for body imaging at 14T. Previously presented fractionated dipole designs for 7T and 10.5T were adapted for 14T. Pulse optimization was performed in volumes with different sizes. In general, the RF shim performance decreases at higher RF frequency. The performance of 14T arrays in ROIs located in the body center is further limited by local SAR limits, as the SAR efficiency ($$B_1^+$$$normalized to $$\sqrt{\operatorname{SAR}_{10g,max}}$$$) is lower in the body center. 4063 Saddle Coil Design for MRI/MRS at 14.1 Tesla: A Favorable Alternative to the Quadrature Birdcage Coil Claudia Christina Zanella1, Jérémie Daniel Clément1,2, Daniel Wenz3, Bernard Lanz1, and Rolf Gruetter1 1Laboratory for Functional and Metabolic Imaging (LIFMET), EPFL, Lausanne, Switzerland, 2School of Biomedical Engineering and Imaging, King's College London, London, United Kingdom, 3Center for Biomedical Imaging – Animal and Imaging Technology (CIBM-AIT), EPFL, Lausanne, Switzerland A single channel 1H saddle coil and a quadrature 1H 8-leg birdcage coil were compared in terms of $$B_1^+$$$homogeneity and $$B_1^+$$$ efficiency for preclinical small-animal imaging at 14.1 Tesla. Electromagnetic field simulations showed that the saddle coil generated a more homogeneous $$B_1^+$$$field for all regions of interest (up to 13.7 mm central disk diameter) than the birdcage coil. Saline phantom measurements showed a more constant flip angle excitation upon multi-slice imaging in axial direction and a 66% higher $$B_1^+$$$ efficiency for the saddle coil.

Session Topic: RF coils
Session Sub-Topic: RF Coils 4
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Engineering

 4064 Multi-loop radio frequency coil elements Roberta Frass-Kriegl1, Sajad Hosseinnezhadian2, Marie Poirier-Quinot2, Elmar Laistler1, and Jean-Christophe Ginefri2 1Division MR Physics, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, 2IR4M (Imagerie par Résonance Magnétique et Multi-Modalités), UMR 8081, Université Paris-Sud/CNRS, Université Paris-Saclay, Orsay, France FDTD simulations and experimental B1 mapping at 3T and 7T demonstrate that multi-loop coils (MLCs), i.e. coils made of small loops in series, provide a significant transmit efficiency boost over conventional loop coils at close distance in sample noise dominated settings. Further away, the performance of MLCs is comparable to single loop coils. The MLC principle brings additional degrees of freedom for coil design and optimization and appears advantageous for single coils as well as individual elements of arrays, especially for applications with large target area and shallow target depth, e.g. skin imaging or high resolution MRI of brain slices. 4065 A custom-made design for integrating a magnetic field monitoring system into a 32ch MRI head coil Yoojin Lee1, Michael Kennedy1, and Zoltan Nagy1 1Laboratory for Social and Neural Systems Research (SNS lab), University of Zurich, Zurich, Switzerland While magnetic field probes can concurrently measure the spatio-temporal magnetic field dynamics during the acquisition of spiral or EPI readout, incorporating such field probes into a head coil requires careful planning and execution. The final set-up must conform to a wide array of boundary conditions for a safe and easy-to-use installation. The specific aims of this project were installing magnetic field probes into a Siemens 32ch coil and make that set-up compatible with a 3T Philips Achieva scanner. It was a high risk/gain project that was achievable only with a widely interdisciplinary approach and the kind input of colleagues. 4066 Dual Band Lattice Balun for Multinuclear MRI Charlotte R Sappo1,2, William A Grissom1,2,3,4, John C Gore1,2,3,4, and Xinqiang Yan2,3 1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 2Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 3Radiology, Vanderbilt University, Nashville, TN, United States, 4Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, United States Baluns are transformers commonly used to connect RF coils to coaxial cables. For dual-tuned RF coils, baluns suppress the common-mode current at the Larmor frequencies for both proton and X-nuclear. This can be realized by utilizing separated single-frequency baluns in series or utilizing dual-band baluns. The LC lattice balun is widely used in RF coils since it can be built directly on the coils’ feeding board and uses minimal space. In this work, we introduce a dual-band Lattice balun design to fit the multinuclear MRI application. We analyzed, simulated and constructed the dual-band lattice balun for the 7T H/Na application. 4067 Active Transmit/Receive Switches for Low Field Magnetic Resonance (<100mT) Charlotte R Sappo1,2,3, Michele N Martin3, Sheng Shen4,5, Neha Koonjoo4,6, Anthony B Kos3, William A Grissom1,2, Matthew S Rosen4,6, and Karl F Stupic3 1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 2Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 3National Institute of Standards and Technology, Boulder, CO, United States, 4Massachusetts General Hospital, A.A. Martinos Center for Biomedical Imaging, Boston, MA, United States, 5Electrical Theory and New Technology, Chongqing University, Chongqing, China, 6Physics, Harvard University, Cambridge, MA, United States Low-field MRI is of increasing interest due to its low cost, improved safety, portability, and low power requirements. A transmit/receive switch is an essential piece of hardware used to dynamically connect a coil to either the transmitter or receiver. Current low field systems typically use passive crossed-diode TR switches. For RF excitation with small flip angles, there may not be sufficient forward bias voltage to turn on the diodes in passive switches, which limits fast imaging and MR fingerprinting.  In this study we evaluate alternative active T/R switches for low power experiments and compare them, at 6.7 and 30 mT. 4068 Flexible Self-decoupled Dual-tuned Array Xinqiang Yan1,2 and John C. Gore1,2 1Department of Radiology, Vanderbilt University Medical Center, Nashville, TN, United States, 2Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States Highly flexible or wearable dual-tuned coil arrays appear to be good choices for increasing the SNR for both protons and X-nuclei and for improving patient comfort. However, complex couplings arise in a dual-tuned coil array. In this work, we have designed self-decoupled coils within a flexible, nested, dual-tuned array, in which impedances are redistributed to achieve high inter-element isolation. 4069 Differential Mode Self-Decoupled Coils Ming Lu1,2,3, William A. Grissom1,2,4, John C. Gore1,2,4, and Xinqiang Yan1,2 1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, 2Department of Radiology, Vanderbilt University Medical Center, Nashville, TN, United States, 3College of nuclear equipment and nuclear engineering, Yantai University, Yantai, China, 4Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States Self-decoupled coils (SDCs) were recently described which can solve complex coupling issues in dense arrays. SDCs have a simple structure and represent a general approach. However, dipole mode in SDCs make it sensitive to the load. In this work, we introduced a differential mode to the design of SDCs to alter the necessary value of Cmode and a coils’ robustness to loading. This differential-mode SDC can be seen as a combination of differential-mode decoupling with self-decoupling. We found that suitable Cmode can choose to increase coil robustness as well as avoid added coil loss. 4070 Routing algorithm for the interconnection of closed wire loops for MR gradient and MR shim coils Philipp Amrein1, Feng Jia1, Sebastian Littin1, and Maxim Zaitsev1 1Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany An automatized solution is presented for the generation of a single wire track from closed loops for complex coil and supporting structure topologies. The algorithm includes a mesh parameterization, a toplogical analysis, route optimization between groups of loops and finally opening and interconnection of the loops. 4071 Compact and Reproducible Microstrip Power Splitters for Array-Compressed Parallel Transmission at 7T Gabriela Gallego1, Charlotte Sappo1,2, Xinqiang Yan2,3, and William A Grissom1,2,3,4 1Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 2Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, 3Department of Radiology, Vanderbilt University, Nashville, TN, United States, 4Department of Radiology, Vanderbilt University Institute of Imaging Science, Nashville, TN, United States Parallel transmission (pTx) with an array of radiofrequency (RF) coils enables spatially uniform excitation with lower SAR in high-field MRI. Performance improves with the number of coils. Currently, 7T scanners have a limited number of transmit channels due to their high cost and complexity. Array-compressed pTx (acpTx) networks comprise unequal power splitters that sit between the transmit amplifiers and coils, enabling a small number of channels to optimally drive a large number of coils. This study presents the design of low-loss unequal power splitter building blocks with minimal size that can be combined in stages for a variety of applications. 4072 A 2kW RF power amplifier for 7T proton imaging with digital pre-distortion Stephan Orzada1,2, Mark E. Ladd1,3,4, and Harald H. Quick1,2 1Erwin L. Hahn Institute for MRI, University of Duisburg-Essen, Essen, Germany, 2High-Field and Hybrid MR Imaging, University Clinic Essen, Essen, Germany, 3Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 4Faculty of Physics and Astronomy and Faculty of Medicine, University of Heidelberg, Heidelberg, Germany A 2 kW peak RF amplifier for 32-channel 7T proton imaging is presented. It is equipped with a digital pre-distortion providing a high linearity up to peak output power. The amplifier can be used for signal bandwidths of 1 MHz, making it suitable for almost any proton MR application. 4073 Experimental Realization of a Clinical Opencage Head Coil for Ultra-High Field MRI Anton Nikulin1, Marc Dubois2,3, Tania S.Vergara Gomez2,3, Djamel Berrahou4, Frank Kober3, Alexandre Vignaud5, Redha Abdeddaim2, Julien de Rosny1, and Abdelwaheb Ourir1 1Institut Langevin, ESPCI Paris, CNRS, PSL University, Paris, France, 2CNRS, Centrale Marseille, Institut Fresnel, Aix Marseille Univ, Marseille, France, 3CNRS, CRMBM, Aix Marseille Univ, Marseille, France, 4Multiwave Innovation SAS, Marseille, France, 5CEA, DRF, JOLIOT, NeuroSpin, UNIRS, Universit´e Paris-Saclay, Gif-sur-Yvette, France A conventional birdcage head coil at 7T is not well suited for certain applications such as motion control. We propose an original coil based on a birdcage with a wide lateral aperture that provides access to the object under examination. We show that a sufficiently homogeneous magnetic field distribution can be obtained by optimizing the current distribution of such an “Opencage”. That coil was optimized using a full wave simulation and tested experimentally. The performance of an Opencage coil was compared to a commercial birdcage coil. Eventually, the Opencage coil is shown as a tradeoff between field homogeneity and access. 4074 An 8-channel Loop Coil Array for Body Imaging Using Coupled Line Phase Shifters at 7T Haiwei Chen1, Lei Guo1, Aurelien Destruel1, Mingyan Li1, Ewald Weber1, Feng Liu1, and Stuart Crozier1 1School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia A large-size loop coil suffers from the current phase inversion along the loop surface and therefore weak the current intensity at the phase inversion points. A new RF coil using coupled line phase shifters is presented for body imaging at 7T MRI. This design can retain an in-phase current along the loop when the perimeter is larger than 1.5$$\lambda$$$($$\lambda$$$ is the wavelength in free space). An 8-channel coil array using this new design is simulated and compared with a conventional loop array. The results indicate that improved $$B^{+}_{1}$$\$ shimming can be achieved in a large region of interest. 4075 Optical Transmission of Digitized MRI Signals Using Delta-Sigma Modulation Mingdong Fan1, Xi Gao2, David Ariando2, Shinya Handa3, Labros Petropoulos3, Xiaoyu Yang3, Hiroyuki Fujita3, Michael Martens1, Robert Brown1, and Soumyajit Mandal2 1Physics, Case Western Reserve University, Cleveland, OH, United States, 2EECS, Case Western Reserve University, Cleveland, OH, United States, 3Quality Electrodynamics (QED), Mayfield Village, OH, United States The electromagnetic interference between conductive cables is becoming an issue as the number of MRI receive channels increases. Optical fibers are seen as one of the potential alternatives. Analog optical links have been investigated due to their relatively simple RF coils structure and minimum modification to the MRI system, but they are often limited by the electrical and optical nonlinearities and degradation of noise figure. In this study, we propose a digital optical transmission system based on delta-sigma modulation (DSM) that aims to provide high dynamic range (DR) for MRI signal transmission. 4076 RF Shim Flexibility with Multi-Surface-Loop Arrays Over Varying Head Geometries Benjamin M Hardy1,2, Yurui Gao2,3, and Adam W Anderson2,3 1Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States, 2Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, 3Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States Magnetic and electric field values are simulated with up to 480 Radio Frequency surface loops 1 cm in radius surrounding realistic head models. The work investigates the capability of B1+ shimming alone with increased degrees of freedom. Transmit efficiency, power limitations, and target homogeneity across the brain volume inform design choices for the array. Evidence of the effects of subject to subject variation can be seen in the optimized shim weights magnitude and phase variation for a choice 256-element geometry optimized over 20 unique head models oriented at 3 head angles. 4077 Feasibility of Forward and Reversed Preamplifier Decoupling (FPD and RPD) Techniques for a Low Field MRI System at 1 MHz Sajad Hosseinnezhadian1, Yonghyun Ha1, Kartiga Selvaganesan1, Charles Rogers III1, Baosong Wu1, Gigi Galiana1, and R. Todd Constable1 1Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT, United States This study investigated the feasibility of applying forward and reversed preamplifier decoupling techniques for low and high impedance coils, respectively, at 1 MHz. At a low field MRI, e.g. 1 MHz, the choice of components needed for interface circuitry together with availability of preamplifiers with low input impedance is challenging. In this study we demonstrated that using a high impedance coil with a lower number of turns achieved better decoupling levels than that of a low impedance coil. In addition, the minimum requirement for the input resistance of a preamplifier at 1 MHz was investigated. 4078 Critical Overlap for Elliptical Arrays Victor Taracila1 and Fraser Robb1 1GE Healthcare, Aurora, OH, United States Multi-channel receive RF coils for MRI are usually comprised of an array of loops. These loops come in various shapes – circles, rectangles, hexagons, octagons, etc. Coil designers try to decrease the coupling between the loops through overlapping – partial overlapping of the two closed contours allows reduction of magnetic coupling between the loops to minimum. This configuration is called a critical overlap. While the critical overlap for circular loops is mentioned in multiple papers, a similar recipe is missing for elliptical loops. In this work we calculate the overlap coefficients for isotropic uniform elliptical arrays.

Session Topic: RF coils
Session Sub-Topic: Dielectric Materials & Metamaterials for Coils
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