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Lena Nohava¹, Michael Obermann¹, Roberta Frass-Kriegl¹, Onisim Soanca¹, and Elmar Laistler^1
1High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria

Keywords: RF Arrays & Systems, RF Arrays & Systems

Form-fitting radiofrequency coil arrays have the potential to enhance the signal-to-noise ratio, enable faster imaging and improve patient comfort in MRI. We developed a flexible modular coil array system for 3T MRI (ModFlex) with 16 receive channels. In neck, spine, ankle and hip imaging, we measured an SNR gain for 4 out of 6 anatomical target regions and similar SNR for 2 out of 6 as compared to commercial reference coils. The coil’s versatility is beneficial for different use cases with varying subject sizes.

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Frederik Abel¹, Ek T. Tan¹, Martijn Lunenburg², Carel van Leeuwen², Thijs van Hooren², Mark van Uden², Catalina Arteaga², Jana Vincent³, Fraser Robb³, Darren R. Lebl¹, and Darryl B. Sneag^1
1Hospital for Special Surgery, New York, NY, United States, ²Tesla Dynamic Coils, Zaltbommel, Netherlands, ³GE HealthCare, Aurora, OH, United States

Keywords: RF Arrays & Systems, RF Arrays & Systems

Conventional cervical coils lack the flexibility to closely conform to the inherently curved neck region, particularly at its head/shoulder junctions. High SNR imaging of the c-spine and extraspinal soft tissues (including small peripheral nerves) relies on close proximity of receive elements to these targeted structures. This study evaluates the performance of a novel, conformal, 23-channel Flexible Array for Cervical & Extraspinal (FACE) 3T MR Imaging with increased flexibility to enhance image quality and SNR compared to conventional coils. SNR measurements on phantoms and high resolution 2D and 3D in vivo c-spine and peripheral nerve neck imaging were performed at 3T.

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Paul-François Gapais^1,2, Michel Luong³, Eric Giacomini¹, Alexandre Vignaud¹, François Nizery⁴, Gabriel Maitre⁴, Sajad Hosseinnezhadian², Marc Dubois², Elodie Georget², and Alexis Amadon^1
1BAOBAB, Université Paris-Saclay/CEA/Joliot/NeuroSpin, GIF-SUR-YVETTE, France, ²Multiwave Imaging SAS, Marseille, France, Metropolitan, ³DACM, Université Paris-Saclay/CEA/IRFU, GIF-SUR-YVETTE, France, ⁴LCAP, CEA/DRF/IRFU/DIS, GIF-SUR-YVETTE, France

Keywords: RF Arrays & Systems, RF Arrays & Systems, Coil

A fully customized 32-channel receive array has been designed, fabricated and evaluated using MR experiments at 7T. The design is made of non-geometrically decoupled loops arranged in two layers of large and small loops. Copper loops are 3D printed from additive manufacturing, preamplifiers are home-built, and an easy implementation procedure is proposed. Receive array performances shows SNR comparable to the Nova Medical reference coil while being superior at the top of the coil and for parallel imaging accelerated in the vertical direction.

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Andrea N Sajewski¹, Tales Santini¹, Anthony DeFranco¹, Boris Keil², Hecheng Jin¹, Jacob Berardinelli¹, Jinghang Li¹, Cong Chu¹, Tiago Martins¹, and Tamer S Ibrahim^1
1University of Pittsburgh, Pittsburgh, PA, United States, ²Institute of Medical Physics and Radiation Protection, TH Mittelhessen University of Applied Sciences, Giessen, Germany

Keywords: New Devices, Neuro

A 60-channel transmit array for 7T neuro MRI was implemented using the Tic-Tac-Toe coil design. The transmit coil and the receive insert are open in the front to promote patient comfort and reduce claustrophobia. By performing RF shimming on three head models, we optimized the coil for a range of ages and head sizes/shapes for use in sTx mode. Simulations, experimental B₁⁺ maps and in-vivo images demonstrate consistency across subjects, showing extended coverage into the temporal lobe, cerebellum, brainstem and C5-C6 spinal cord segments. High quality images are currently being acquired using this coil in over 30 human studies. 

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Keywords: RF Arrays & Systems, RF Arrays & Systems

We evaluated in simulation and experimentally the effects that the insertion of a 32-channel sleeve antenna receiver array has on the B1+ and SAR performance of a 447 MHz/10.5 T 16-channel loop transmitter array.  For this we carefully developed accurate models of both the 16-channel loop transmitter and the 32-channel sleeve antenna receiver, compared simulated with experimental B1+ and evaluated the expected SAR efficiency of the 16-channel loop transmitter array with and without the 32-channel sleeve antenna receiver array insert.

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Russell Luke Lagore¹, Andrea Grant¹, Lance DelaBarre¹, Edward J Auerbach¹, Matt Waks¹, Steve Jungst¹, Steen Moeller¹, Jerahmie Radder¹, Alireza Sadeghi-Tarakameh¹, Yigitcan Eryaman¹, Pierre-Francois Van de Moortele¹, Gregor Adriany¹, and Kamil Ugurbil^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

Keywords: RF Arrays & Systems, RF Arrays & Systems

Described is a 128-channel receive (Rx) array for 10.5T brain imaging, comprised of 120 small Rx loops and 8 of the 16 transmitter elements used as receivers. The coil is compared to another 10.5T 64-Rx array and to 7T 32- and 64-Rx arrays. The principal benefit for the same field strength was improved parallel imaging. Secondarily, important engineering innovations are demonstrated to suppress transmit/receive interactions and optimize transmit efficiency.  Modest improvements to peripheral SNR were achieved for the 10.5T 128-Rx over 64-Rx array. A 50% improvement in central SNR was realized with the use of transmitter elements as receivers.

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Bernhard Gruber^1,2,3, Jason P. Stockmann^1,4,5, Azma Mareyam¹, Yulin Chang⁶, Boris Keil⁷, Berkin Bilgic^1,4, Alexander Beckett^8,9, David A. Feinberg^8,9, and Lawrence L. Wald^1,4,5
1A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States, ²High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University Vienna, Vienna, Austria, ³BARNLabs, Muenzkirchen, Austria, ⁴Harvard Medical School, Boston, MA, United States, ⁵Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States, ⁶Siemens Medical Solutions USA Inc., Malvern, PA, United States, ⁷Department of Life Science Engineering, Institute of Medical Physics and Radiation Protection, Mittelhessen University of Applied Sciences, Gießen, Germany, ⁸Advanced MRI Technologies, Sebastopol, CA, United States, ⁹Helen Wills Neusoscience Institute, University of California, Berkeley, CA, United States

Keywords: RF Arrays & Systems, RF Arrays & Systems

The performance of a 128-channel Rx-only 7T brain array was evaluated using simulations and measurements. SNR and g-factor maps show a significant performance increase for highly accelerated imaging in cortical areas from a combination of improved peripheral unaccelerated SNR and g-factor. Measured SNR in cortical areas increased by 42% from 32- to 128-ch and 18% from 64- to 128-ch. The 1/g-factor maps show an improved mean and a tighter distribution, with both effects becoming more pronounced at higher accelerations. At 6x2-fold the 128-channel array has 17.9% g-factor benefit over the 64-ch, and a 48.2% benefit over the 32-ch array.

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Georgiy Alekseevich Solomakha¹, Dario Bosch ^1,2, Klaus Scheffler^1,2, and Nikolai Ivanovich Avdievich ^1
1High-field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Department for Biomedical Magnetic Resonance, University of Tübingen, Tuebingen, Germany

Keywords: RF Arrays & Systems, RF Arrays & Systems

Arrays of dipole antennas were recently introduced as transceiver RF coils for human head imaging at UHF as a simple and robust alternative to loop arrays. Due to the head size, dipoles should be significantly shorter than λ/2 at working frequency. Short dipoles suffer from high SAR and insufficient brain coverage. In addition, since head arrays are usually placed on rigid holders, the resonance frequency of dipoles change drastically with head size variation. In this work, we developed a coaxial dipole array for human head imaging at 9.4T. The developed coil provides whole-brain coverage, low SAR, and low frequency variation.  

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Bei Zhang¹, Daniel Lowrance¹, David Zaha¹, Manoj Kumar Sarma¹, Michael Douglas Nelson², and Anke Henning^1
1Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States, ²The University of Texas at Arlington, Arlington, TX, United States

Keywords: Non-Array RF Coils, Antennas & Waveguides, Skeletal, 31P/1H Dual-tuned, NIRS

In this work, we present a 3T ³¹P/¹H calf coil with two interleaved and co-centered birdcages in one layer to provide homogenous transmit fields and good SNR for both ³¹P and ¹H nuclei. In addition, the coil design allows for integration of a Near-infrared spectroscopy (NIRS) probe for simultaneous NIRS and MRI readouts during exercise. Simulation and phantom experimental results show that the coil provides homogeneous transmit and receive fields. In vivo experiment show that the coil provide good SNR for both ³¹P MRS and ¹H MRI and MRS

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Michael Obermann¹, Lena Nohava¹, Roberta Frass-Kriegl¹, Onisim Soanca¹, Jean-Christophe Ginefri², Jacques Felblinger³, and Elmar Laistler^1
1High Field MR Center, Medical University of Vienna, Vienna, Austria, ²Laboratoire d’Imagerie Biomédicale Multimodale Paris Saclay (BioMaps), CEA, CNRS, Inserm, Université Paris-Saclay, Paris-Saclay, France, ³IADI, Inserm, Université de Lorraine, Nancy, France

Keywords: New Devices, RF Arrays & Systems

Recently, we introduced the “BraCoil”, a wearable coil for prone and supine breast imaging designed to overcome several shortcomings in clinical breast MRI. Here, we present in vivo performance tests on 12 volunteers with different breast volumes ranging from 495 mL (bra size 70A) to 3020 mL (90D). SNR gain up to a factor of three over a commercial breast coil was found. Acceleration factors up to 6x4 can be used with reasonable g-factors. High-quality in vivo images with different contrasts are presented.

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Kyle M Gilbert^1,2, Emily S Nichols^3,4, Joseph S Gati^1,2, and Emma G Duerden^3,4,5
1Centre for Functional and Metabolic Mapping, Western University, London, ON, Canada, ²Department of Medical Biophysics, Western University, London, ON, Canada, ³Applied Psychology, Western University, London, ON, Canada, ⁴Western Institute for Neuroscience, Western University, London, ON, Canada, ⁵Department of Pediatrics, Western University, London, ON, Canada

Keywords: RF Arrays & Systems, RF Arrays & Systems

This abstract presents an adjustable RF coil designed for imaging three-month-old infants to three-year-old toddlers, where motion and variance in head size can be detrimental to image quality. The coil is designed with an open face to allow for the use of camera or motion tracking systems. The tailored RF coil produced higher SNR and lower geometry factors than adult coils. Accelerated protocols can now be combined with prospective motion correction, thereby improving the success rate of imaging infant and toddler populations.

Sri Kirthi Kandala¹, Kwanjoon Song², and Sung-Min Sohn^1
1Arizona State University, Tempe, AZ, United States, ²Yonsei University, Gangwon-do, Korea, Republic of

Keywords: Non-Array RF Coils, Antennas & Waveguides, New Devices, Liquid metal RF coil

In this work, we present a novel inflatable radio-frequency receive coil for Magnetic Resonance Imaging at 7T. A small sample was imaged with and without inflation, and the overall signal-to-noise ratio of the sample was improved by 12.7% in dB with inflation. This coil design will offer many opportunities in the field of endorectal imaging, imaging for irregular sample shapes, and reducing motion artifacts. Inflation also changes the tuning and matching conditions, which compensate for loading effects by precisely adjusting the  air volume inside the cavity.

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Kazuya Okamoto¹, Sojuro Kato², Mark Spring³, Yoshinori Hamamura⁴, Daisuke Horio⁵, Yu Tanaka⁵, Shun Sugimoto⁵, and Kazunari Watanabe^5
1MRI Systems Development Department, CANON Medical Systems Corporation, Kawasaki, Japan, ²CANON Medical Systems Corporation, Kawasaki, Japan, ³Platform Technology, Canon Medical Research USA Inc., Vernon Hills, IL, United States, ⁴MRI Systems, Canon Medical Research USA Inc., Mayfield Village, OH, United States, ⁵Digital Business Platform Development Headquarters, Canon Inc., Tokyo, Japan

Keywords: RF Arrays & Systems, RF Arrays & Systems, wireless

We prototyped a new acquisition board (NAB) equipped with wireless signal transmission modules, and connected it to the reception RF coil and the scanner system. The configuration enabled that the transmission of the 8-ch reception signal data from the RF coil and the system clock was carried out between boards wirelessly. Finally, two-dimensional SE images were obtained without deterioration in image quality.

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N Reid Bolding¹, Chris Vaughn², Aria Patel¹, Snow Lin¹, Andrew Dupuis¹, William A Grissom², and Mark A Griswold^1
1Case Western Reserve University, Cleveland, OH, United States, ²Vanderbilt University, Nashville, TN, United States

Keywords: RF Arrays & Systems, Low-Field MRI, Gradient Free Imaging

We present here the development of a wireless flat amplitude 2 MHz radiofrequency transmitter for under $100, focusing on the pulse synthesis stage. We gave special consideration to simplifications that can be made with high speed digital synthesis and switch mode amplifier topology. This is a component of a distributed transmit receive system, meeting the special requirements of gradient free low field quantitative imaging techniques, such as selective encoding through nutation and fingerprinting (SENF).

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Keywords: New Devices, Focused Ultrasound

MRI is commonly employed to assess microbubble-mediated focused ultrasound (FUS) treatment outcomes, but is restricted to post-treatment evaluations due to its low temporal resolution. Here, we describe a modular sparse hemispherical transmit/receive phased array for microbubble-mediated FUS brain therapy and simultaneous 3D passive cavitation imaging (PCI) for real-time intraoperative treatment monitoring and control. The device was evaluated via MR-guided FUS experiments in rabbits. The utility of 3D PCI in calibrating FUS exposure levels and predicting MRI-inferred tissue damage volume distributions resulting from high target level sonications was demonstrated.