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Edith Valle¹, Seelay Tasmim², Mary P. McDougall^1,2, and Taylor H. Ware^2,3
1Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States, ²Biomedical Engineering, Texas A&M University, College Station, TX, United States, ³Materials Science & Engineering, Texas A&M University, College Station, TX, United States

Keywords: Non-Array RF Coils, Antennas & Waveguides, Hybrid & Novel Systems Technology

The development of highly sensitive multinuclear RF coils for MRI/S is challenging because most current multi-tuning techniques involve the addition of lossy components. Although it is possible to optimize for a particular nucleus, usually non-¹H, multinuclear coils have lower SNR than their single-tuned counterparts. We investigate a novel switching system that uses stimuli-responsive materials. The coils with the proposed switching method had a decrease of <26% in Q when compared to single-tuned coils. As a result, we demonstrated a promising alternative to traditional switching techniques. 

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Joseph Busher¹ and Mary P. McDougall^1,2
1Biomedical Engineering, Texas A&M University, College Station, TX, United States, ²Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States

Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides

Multi-frequency coils are typically known to have substantial losses as compared to their single-tuned counterparts. Here we investigate sensitivity tradeoffs of triple-tuned (¹H-²³Na-³¹P) trap designs on receive coils in a tightly controlled experiment to isolate the sensitivity effects of the traps. Triple-tuned LCC traps were shown to have significant improvement in sensitivity for ²³Na and ¹H as compared to an LC trap design. The increase came at the expense of ³¹P sensitivity, however continued optimization of the trap design will likely further improve the final experimental SNR.

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Nan Li^1,2, Feng Du^1,2, Xiaoliang Zhang³, Xin Liu^1,2, Hairong Zheng^1,2, and Ye Li^1,2
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, Shenzhen, China, ²Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen, China, Shenzhen, China, ³Department of Biomedical Engineering, State University of New York, Buffalo, NY, United States, Buffalo, NY, United States

Keywords: RF Arrays & Systems, RF Arrays & Systems

    As the lower natural abundance of X-nuclei, it is important to enhance that the signal-to-noise ratio (SNR) of the X-nuclei is as high as possible by designing a well-designed multiple-tuned coils. In this study, a new triple-tuned RF coil system capable of ¹H / ¹⁹F / ²³Na imaging was proposed. The performance of the triple-tuned coil was evaluated compared to their counterpart single-tuned coils by the numerical electromagnetic simulation. Imaging tests at 3T MRI were performed on the phantom by using the triple-tuned RF coil.

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Luca Nagel¹, Geoffrey J. Topping¹, and Franz Schilling^1
1School of Medicine, Klinikum rechts der Isar, Department of Nuclear Medicine, Technical University of Munich (TUM),, Munich, Germany

Keywords: RF Arrays & Systems, RF Arrays & Systems

Cryogenically-cooled ¹³C radiofrequency (RF) coils (cryocoils) improve SNR by reducing thermal coil noise compared to room-temperature coils. Coil geometry impacts B₁ patterns, which impact experiment design and must be characterized. The sensitivity profiles of a linear and a quadrature coil were characterized with varied RF powers, which is complicated by transmit B₁ variation with position and resulting excitation variations. The sensitivity was compared to a room-temperature volume resonator. The quadrature cryocoil configuration offers better B₁ uniformity but lower SNR closest to the coil compared to the linear configuration, both have an overall better SNR performance compared to the volume resonator.

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Veronika Cap¹, Martin Meyerspeer¹, Sigrun Roat¹, Elmar Laistler¹, and Roberta Frass-Kriegl^1
1Division MR Physics, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria

Keywords: RF Arrays & Systems, RF Arrays & Systems, dipoles, simulation

Different dipole antenna types as ¹H transmit elements for metabolic ¹H/³¹P MRS studies of the human calf were investigated. In simulations, the dipole elements and a loop coil were compared in terms of transmit efficiency and SAR. A three-element array of the best-performing design was simulated and constructed, and its transmit performance was found to be comparable to a four-element loop array. Investigating the interaction between a dipole transmit element and a receive-only loop placed underneath, efficient geometric decoupling was observed. This can be exploited to improve the receive sensitivity (homogeneity, depth) by using transceiver dipoles together with receive-only loops.

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Feng Du^1,2, Nan Li^1,2, Xiaoliang Zhang³, Xin Liu^1,2, Hairong Zheng^1,2, and Ye Li^1,2
1Paul C. Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, Shenzhen, China, ²Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province, Shenzhen 518055, Guang Dong, China, Shenzhen, China, ³Department of Biomedical Engineering, State University of New York, Buffalo, NY, United States, Buffalo, NY, United States

Keywords: RF Arrays & Systems, New Devices

    Multinuclear MRI has been demonstrated as a crucial tool for comprehensively characterizing tumor pathology and monitoring tumor treatment response as it can provide biochemical, physical, and functional as well as structural information. The objective of this work is to develop a quadruple-nuclear transceiver coil array for ¹H/¹⁹F/²³Na/³¹P MRI at 3T to simultaneously detect multinucleal signals. The phantom studies were performed on self-developed 3T MRI system to verify the performance. These results proved that uniform excitation and highly sensitive acquisition in the region of interest were achieved by utilizing the proposed RF coil and indicated the fesibility for multinuclear MRI applications.

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Chenhao Sun¹, Courtney Bauer¹, Jue Hou¹, and Steven M. Wright^1
1Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States

Keywords: RF Arrays & Systems, RF Arrays & Systems, Multi-Nuclei, multinuclear, decoupling

This study proposes a novel low-complexity decoupling approach for multi-nuclei receive array coil design. Instead of using narrowband LC networks and isolation preamplifiers, a preamplifier with high input impedance can be used to decouple receive coils while maintaining most SNR. A broadband impedance matching network consist of LCC multi-tuned circuit and transformer was developed to interface the coil with a high Z preamplifier. The proposed setup has achieved more than 15dB of decoupling over a range of 25MHz. The prototype simultaneously yielded 73.6% and 91.9% of SNR at 2H and 23Na when compared to the conventional single-tuned preamplifier decoupling methods.

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Georgiy Alekseevich Solomakha¹, Felix Glang¹, Theodor Steffen², Klaus Scheffler^1,3, and Nikolai Ivanovich Avdievich ^1
1High-field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Electronical Workshop, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ³Department for Biomedical Magnetic Resonance, University of Tübingen, Tuebingen, Germany

Keywords: RF Arrays & Systems, RF Arrays & Systems

Recently developed dynamic parallel imaging, i.e. rapid modulation of element's sensitivities during acquisition, greatly improved the performance of the method. In this work, sensitivity profiles of dipole elements were electronically reconfigured by varying impedances of lumped element circuits connected in series with the dipoles . This required a large number of DC wires directly connected to the dipoles. In the present work, we developed, constructed, and evaluated a dynamically reconfigurable 8-element coaxial dipole array for brain imaging at 9.4T. Our design eliminates the DC wires directly connected to the dipoles and, hence, substantially simplifies further increasing the number of receive channels.   

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Yu-Lung Tang¹, Hsin-Ju Lee^2,3, and Fa-Hsuan Lin^2,3
1Timwave Technologies Company Limited, Taipei, Taiwan, ²Sunnybrook Research Institute, Toronto, ON, Canada, ³University of Toronto, Toronto, ON, Canada

Keywords: RF Arrays & Systems, RF Arrays & Systems

The decoupling between coils significantly impacts the amount of independent information between channels in a receiver coil array. Using a pre-amplifier with a low input impedance is limited by the technology in achieving the lowest possible impedance, typically around a few ohms. Here we propose a strategy to improve the decoupling between coil elements in a receiver array by increasing the impedance of the coil system. Simulations and bench measurements show that increasing the impedance from a typical 50 ohm to around 1,000 ohm can increase the decoupling by 25 dB.

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Seyedamin Hashemi¹, Sri Kirthi Kandala¹, and Sung-Min Sohn^1
1School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States

Keywords: RF Arrays & Systems, Phantoms, Receive coil, flexible coil, loaded coil

This study presents a novel receive radiofrequency coil that enhances the signal-to-noise-ratio (SNR) and field-of-view (FOV) in magnetic resonance images. The fabricated coil is loaded by a mixture of dielectric material (TiO2) and an elastomer offering stretchability and flexibility. The functionality of the coil compared to a typical surface coil was assessed using phantom imaging at 7T. The SNR (in dB), signal intensity, and uniformity are improved by 14.75%, 25%, and 87.76% by using a TiO2-loaded coil, respectively. This design method will be invaluable for uneven sample shapes and a very close place to a subject.

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Faezeh Rahimi^1,2, Thomas Wilhelm Eigentler^1,3, Jason M. Millward^1,4, Pirus Ghadjar⁵, and Thoralf Niendorf^1,4,6
1Berlin Ultrahigh Field Facility, Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, ²Theoretische Elektrotechnik Institut Hochfrequenz- und Halbleiter-Systemtechnologien, Technische Universität Berlin, Berlin, Germany, ³Chair of Medical Engineering, Technische Universität Berlin, Berlin, Germany, ⁴a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine, Berlin, Germany, ⁵Clinic for Radiation Oncology, Charite’ Universitätsmedizin, Berlin, Germany, ⁶MRI.TOOLS GmbH, Berlin, Germany

Keywords: RF Arrays & Systems, Interventional Devices, SAR distribution, Focal Heating, Hyperthermia, Brain Thermal MR at 7T

Thermal Magnetic Resonance (ThermalMR) uses an RF-applicator to add a thermal intervention dimension to a diagnostic imaging device. Optimizing the performance of RF applicator configurations can eventually improve the performance of ThemalMR. This work examines the feasibility of multi-channel RF applicators using broadband Self-Grounded Bow-Tie (SGBT) antenna building blocks. The focus is on enhancing focal RF power deposition in a target volume by using a multi-channel helmet RF array configuration versus conventional annular RF arrays.  Our preliminary findings obtained for the human head voxel model Duke show improved target coverage of high SAR_10g and high temperature for the helmet configuration. 

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Ming Lu¹, Zhipeng Cao^2,3, and Xinqiang Yan^2,3
1College of Nuclear Equipment and Nuclear Engineering, Yantai University, Yantai, China, ²Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, ³Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States

Keywords: Parallel Transmit & Multiband, High-Field MRI

This work is aiming to answer which multi-row self-decoupled array outperforms in parallel transmission to generate a uniform transmit RF field (B₁⁺).

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Wolfgang Loew¹, Virginia Van Horne², Peter van der Meulen³, and Charles Dumoulin^1
1Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States, ²Innovation Ventures, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States, ³Philips Healthcare, Best, Netherlands

Keywords: Whole Body, New Devices

A platform was developed for ¹²⁹Xe applications allowing the use of an insertable whole-body transmit/receive coil by itself or in combination with a ¹²⁹Xe phased array coil. Experiments were performed in a 3T MRI scanner without modification of the scanner’s ¹H body coil. ¹²⁹Xe imaging was performed with a loader phantom and a xenon Boltzmann phantom in both configurations. 

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Peter Truong¹, Helmut Stark², Agessandro Abraham^3,4, Lorne Zinman^3,5, and Jamie Near^1,6
1Physical Sciences Research Platform, Hurvitz Brain Sciences Program, Sunnybrook Research Institute, Toronto, ON, Canada, ²Stark Contrast, Erlangden, Germany, ³Evaluative Clinical Sciences, Hurvitz Brain Sciences Research Program, Sunnybrook Research Institute, Toronto, ON, Canada, ⁴Department of Medicine (Neurology), Sunnybrook Health Sciences Centre and University of Toronto, Toronto, ON, Canada, ⁵Institute of Medical Science and Rehabilitation Sciences Institute, University of Toronto, Toronto, ON, Canada, ⁶Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

Keywords: Non-Array RF Coils, Antennas & Waveguides, Challenges

Join us as we take you on a journey in the development of a Tx/Rx 31P birdcage head coil. Even though there is a wealth of available knowledge explaining the theory of MRI RF coil design, there are many unforeseen situations one will encounter in practice. The road for coil development is filled with many valuable lessons. We hope to provide a practical guide for new builders by describing our experiences in coil design, construction, and troubleshooting. 

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Xin Li¹, Guangle Zhang¹, Wei Zhu¹, Xiaoliang Zhang², Xiao-Hong Zhu¹, and Wei Chen^1
1Department of Radiology, University of Minnesota, Minneapolis, MN, United States, ²School of Engineering and Applied Sciences, University of Buffalo, Buffalo, NY, United States

Keywords: Non-Array RF Coils, Antennas & Waveguides, RF Arrays & Systems

Current state-of-the-art RF coils for X-nuclear MRS/MRI studies typically use two separate sets of RF coils operating at the X-nuclear and proton frequencies, respectively. Here, we introduce a new coil concept whereby large-size loop coil with split capacitors which can be simultaneously tuned and matched to ¹⁷O and ¹H Larmor frequencies for 7T human imaging application. Importantly, this novel coil exhibits excellent performance in proton and X-nuclear imaging, therefore, it provides a simple RF coil solution, particularly for ultrahigh field (UHF) multinuclear brain MR imaging applications.

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Shuyang Chai^1,2, John Gore^1,2, and Xinqiang Yan^1,2
1Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States

Keywords: RF Arrays & Systems, RF Arrays & Systems

A novel flexible and stretchable coil based on the self-decoupling technology is proposed. It can be stretched and bent to match the shape of the human anatomy of interest, exhibiting high SNR.  A 4 coil array was built and tested at different stretching (horizontally and vertically), and on different anatomies (torse, thigh, head), showing a strong robustness.

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Daniel Wenz^1,2 and Thomas Dardano^1,2
1CIBM Center for Biomedical Imaging, Lausanne, Switzerland, ²Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland

Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Dielectric resonator, loo-dipole

The goal of this work was to demonstrate that performance of multi-channel dielectric resonator antenna arrays for brain MRI at 7T can be substantially improved using a novel multi-feed, loop-dipole coupling mechanism. Simulations were conducted for different rectangular DRA geometries and dielectric constants. Three RF feed types were investigated: loop-only, dipole-only and loop-dipole. 16-channel, loop-dipole rectangular DRA arrays provided significant gains in B₁⁺, SAR efficiency and SNR vs. 8-channel bow-tie antenna array. The feasibility of multi-feed, loop-dipole approach was for a 24-channel DRA array was demonstrated.

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Menglu Wu^1,2, Jérémie Clément^1,3, Jules Vliem^1,4, David Leitão ¹, Raphael Tomi-Tricot^1,2,5, and Özlem Ipek^1,2
1Biomedical Engineering, King's College London, London, United Kingdom, ²London Collaborative Ultra high field System (LoCUS), King's College London, London, United Kingdom, ³System Technologies, Siemens Healthcare GmbH, Erlangen, Germany, ⁴Electrical Engineering, Technical University of Eindhoven, Eindhoven, Netherlands, ⁵MR Research Collaborations, Siemens Healthineers, Frimley, United Kingdom

Keywords: RF Arrays & Systems, Non-Proton

7T MRI has great potential to enhance the sensitivity to ²³Na, allowing access to functional and anatomical information when combined with proton imaging. We introduce an RF coil design of a 16-channel Tx/Rx head array composed of eight proton dipoles and eight overlapping sodium loops for 7T. The initial results were acquired on phantoms with comparable performance for both nuclei, and a 40% B₁⁺ gain was reported in sodium channels against the commercial coil. All elements were well-decoupled (-7.2dB to -36dB) without implementation of multiple layers or RF shield, paving the way for future simultaneous ¹H/²³Na MRI acquisition at 7T.

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Ming Lu¹, Shuyang Chai^2,3, and Xinqiang Yan^2,3
1College of Nuclear Equipment and Nuclear Engineering, Yantai University, Yantai, China, ²Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, ³Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States

Keywords: RF Arrays & Systems, High-Field MRI

The Dipole antenna, which has a long longitudinal coverage and deep penetration, has demonstrated a better transmit efficiency for spinal cord imaging compared to the standard loop coil. However, owing to the inevitable coupling, the number of dipoles is highly limited. In this work, we find that the number of dipoles could be doubled if they are be shortened in different ways and arranged to interleave. An 8-channel dipole array consisting of 4 inductor-shortened dipoles and 4 folded dipoles was designed and numerically investigated for 7T lumbar spinal cord imaging.

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Camille Dubuc^1,2, Aimé Labbé¹, Sina Marhabaie¹, Clément Thibault^3,4, Jean-Christophe Ginefri¹, Javier Briatico⁵, and Marie Poirier-Quinot^1
1Université Paris-Saclay, BioMaps, ORSAY, France, ²Thales Research & Technology, Palaiseau, France, ³Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France, ⁴Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, ⁵Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France

Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Superconducting material, Decoupling

A promising strategy to tackle the issue of decoupling High-Temperature Superconducting (HTS) surface coils during emission is to exploit nonlinearities of the HTS coil electromagnetic response. In this work, we present the first Magnetic Resonance Images acquired with a decoupled HTS surface coil and the required coil’s features to obtain these images. The change of the HTS coil Q-factor values leads to different decoupling levels (DL) of the HTS coil and the presence or absence of B1 artifacts on the images.