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

Cryogenically cooled transmit/receive radiofrequency coils (cryocoils) improve the signal-to-noise ratio (SNR) compared to conventional RF coils by minimizing thermal coil noise. The SNR of a cryoprobe, a surface coil at room temperature and a volume coil was assessed using chemical shift imaging of a  ¹³C-urea phantom. Using the cryocoil an SNR improvement up to a factor of 10 compared to conventional coils was observed. In addition, a proof-of-concept in vivo experiment using the ¹³C-cryocoil for detection of the metabolic turnover of hyperpolarized ¹³C-pyruvate was successfully performed.
 

Vitaliy Zhurbenko¹, Juan Diego Sánchez Heredia¹, Wenjun Wang¹, and Jan Henrik Ardenkjær-Larsen^1
1Technical University of Denmark, Kgs. Lyngby, Denmark

Imaging of low-abundance nuclei could benefit from close proximity detecting coils. Close proximity is conveniently achieved using flexible arrays, which conform to the shape of the subject. In this work, a design of an 8-element ultra-flexible array for ¹³C imaging is presented. Each array element includes a low-noise preamplifier with ¹³C/¹H active and passive decoupling, as well as high-power pulse protection circuits. The array is lightweight and easy to handle. The design approach is directly scalable to larger size arrays.

Adam Maunder¹, Ashwin Iyer², and Nicola De Zanche^1
1Oncology, Medical Physics, Cross Cancer Institute, University of Alberta, Edmonton, AB, Canada, ²Electrical and Computer ENgineering, University of Alberta, Edmonton, AB, Canada

Well-established and emerging methods of ²³Na sodium imaging in the brain benefit from high field strength, but require imaging sequences that are constrained by specific absorption rate (SAR) limits. Additionally, concurrent proton imaging is desirable for complementary anatomical/structural information. Here, we present a novel metamaterial liner-based MR coil for ²³Na/¹H imaging at 4.7 T, consisting of longitudinally-spaced rings that alter the effective electromagnetic properties between the liner and outer RF shield (waveguide boundary). In simulation, the metamaterial liner was found to produce lower local 10g averaged SAR for the same mean transmit field relative to a conventional birdcage coil.

Viktor Puchnin¹, Viacheslav Ivanov¹, Mikhail Gulyaev², and Mikhail Zubkov^1
1Department of Physics and Engineering, ITMO University, Saint-Petersburg, Russian Federation, ²Faculty of Fundamental Medicine, Lomonosov Moscow State University, Moscow, Russian Federation

The RF-coils of small-animal scanners often limit the range of accessible nuclei to single- or double-nuclear scanning. Here, a multi-tuneable RF-coil design is investigated. The design comprises a butterfly-type RF-coil for ¹H, and a multi-tuneable coil for X-nucleus imaging. The coil assembly is tested in a 7 T scanner. ¹H and X-nucleus field maps show good matching between the simulation and experiment. Imaging and spectroscopy experiments provide well-resolved images as well as distinctive spectral peaks corresponding to the phantom compounds. The presented imaging method with single coil assembly is considered a promising expansion of heteronuclear imaging.

Cameron Nowikow¹, Paul Polak¹, Norman B. Konyer², Natalia Nikolova³, and Michael D. Noseworthy^1,2,3
1School of Biomedical Engineering, McMaster University, Hamilton, ON, Canada, ²Imaging Research Centre, St. Joseph's Healthcare, Hamilton, ON, Canada, ³Electrical and Computer Engineering, McMaster University, Hamilton, ON, Canada

There is an intrinsic lack of SNR in ²³Na-MRI images compared to that of proton-based MRI. It is possible that RF coil geometry can affect the acquired images' SNR. This abstract is an investigation into the B₁⁺ field characteristics of a Koch snowflake fractal RF surface coil to see if the produced field is more homogeneous than that of a standard circular surface coil which could lead to higher SNR in the resultant ²³Na images. It was found that the circular geometry produced a more homogeneous field, along with higher SNR than the fractal coil.

 

Wenjun Wang¹, Juan Diego Sánchez Heredia², Vitaliy Zhurbenko¹, and Jan Henrik Ardenkjær Larsen^2
1Department of Electrical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark, ²Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark

A cryogenic coil and a dedicated cryostat for ¹³C human head imaging is developed. A 1.90-fold SNR enhancement over a room temperature coil is observed experimentally. To verify the retention of SNR enhancement in arrays, a 4-channel cryogenic coil array and another cryostat are also developed. The superior performance to a room-temperature array is confirmed experimentally.

Xin Li¹, Hannes M. Wiesner¹, Matt Waks¹, Xiao-Hong Zhu¹, and Wei Chen^1
1Center for magnetic Resonance Research (CMRR), Department of Radiology, University of Minnesota, Minneapolis, MN, United States

In vivo ³¹P MRS imaging (MRSI) is important for studying cerebral energy metabolism, intracellular NAD and redox ratio. However, it is challenging to achieve high spatiotemporal resolution owing to limited ³¹P sensitivity and low phosphorus metabolites concentration. We had demonstrated that ultrahigh field (UHF) could significantly improve the ³¹P-MRS sensitivity and spectral resolution. In this study, we designed and constructed a loop-dipole ³¹P-¹H probe, which could operate at 7T and 10.5T for quantitative comparison of ³¹P MRSI signal-to-noise ratio (SNR) between the two fields. We found that the apparent SNR at 10.5T was significantly higher than that of 7T.

Zhe Wang¹, Fangrong Zong², Cheng Fang¹, Wenhui Yang^3,4, Shasha Yue¹, Yan Hou², Zehui Li², Tianyu Xie², Kun Zhang², Yan Zhuo^1,4,5, Xiaohong Joe Zhou⁶, Xiaoliang Zhang⁷, and Rong Xue^1,4,8
1State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, ²Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, ³Institute of Electrical Engineering Chinese Academy of Sciences, Beijing, China, ⁴University of Chinese Academy of Sciences, Beijing, China, ⁵CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Beijing, China, ⁶Center for MR Research and Departments of Radiology, Neurosurgery and Bioengineering, University of Illinois at Chicago, Chicago, IL, United States, ⁷Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States, ⁸Beijing Institute of Brain Disorders, Beijing, China

In this study, a nested dual-tuned proton-sodium multi-channel loop-array transceiver coil was designed and constructed for 9.4T MRI, which could provide images for both proton and sodium at the same location. This coil adopts nested structure, which contains 8-channel transceiver loop elements respectively, and each loop is equipped with an independent transmit/receive circuit. The coil array was simulated for B1 field distribution and was further tested on a 9.4T whole-body MRI platform with  home-built spectrometer. Proton and sodium images on a water phantom were successfully collected on this system with high quality.

Juan Diego Sánchez Heredia¹, Wenjun Wang^1,2, Vitaliy Zhurbenko², and Jan Henrik Ardenkjær-Larsen^1
1Department of Health Technology, Technical University of Denmark (DTU), Kgs. Lyngby, Denmark, ²Department of Electrical Engineering, Technical University of Denmark (DTU), Kgs. Lyngby, Denmark

We propose a design concept for flexible human head coil arrays applicable to a wide frequency range. Electrically, the design relies on high decoupling obtained through a controlled high mismatched connection to the low-impedance preamplifiers. Mechanically, the array is built into a neoprene EEG cap, and made of regular-copper flexible wire. The array layout is designed to have an axis to stretch along, therefore allowing tight fit to a variety of human-head sizes. A 32-channel prototype for ¹³C at 3T (32.1 MHz) is presented and evaluated, showing SNR performance superior to a ¹³C-dedicated volume coil.

Nikolai Avdievich¹, Georgiy Solomakha², Loreen Ruhm¹, Anke Henning^1,3, and Klaus Scheffler^1
1High-field Magnetic Resonance, Max Planck Institute for Bilogical Cybernetics, Tübingen, Germany, ²Physics and Engineering, ITMO University, St. Petersburg, Russian Federation, ³Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States

Dipole antennas have been successfully utilized at ultra-high fields (UHF, >7 T) for human body and head imaging. Combining X-nuclei surface loops and ¹H dipoles can substantially simplify the design of a double-tuned UHF human head coil. In this work, we developed and constructed a novel ¹³C/¹H human head 9.4 T array coil consisting of eight ¹³C surface loops and eight ¹H folded-end dipoles surrounding the head. We showed that coupling between loops and dipoles can be minimized by placing four ¹H traps into each ¹³C loop. The new coil demonstrated an improved ¹H longitudinal coverage and reasonable Tx efficiency.

Yue Zhu^1,2 and Xinqiang Yan^1,2
1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States

A dual band Lattice balun was proposed previously, which holds the promise of removing common mode current for both frequencies in dual-tuned MRI coils with a single interfacing unit. However, the previously fabricated unit had a considerable insertion loss at the proton Larmor frequency. In this work, we analyzed how each lumped element will affect this device's performance and optimized the circuit performance based on the analysis.

Joseph Busher¹, Chenhao Sun², Travis Carrell¹, Edith Valle², Steven M. Wright^1,2, and Mary 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

This work describes two interleaved nine-leg linear birdcages for geometric decoupling from a double-tuned planar array for 1H and 23Na at 4.7T.  An asymmetric design was chosen to create aligned fields to simultaneously decouple the receive array from the two transmit birdcages.  This straightforward design provides sufficient decoupling from coils in all six positions in the final array configuration and enables multinuclear multichannel imaging experiments. 

Juan Diego Sánchez Heredia¹, Wenjun Wang^1,2, James T. Grist^3,4,5, Esben Søvsø Szocska Hansen⁶, Christoffer Laustsen⁶, Vitaliy Zhurbenko², and Jan Henrik Ardenkjær-Larsen^1
1Department of Health Technology, Technical University of Denmark (DTU), Kgs. Lyngby, Denmark, ²Department of Electrical Engineering, Technical University of Denmark (DTU), Kgs. Lyngby, Denmark, ³Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom, ⁴Oxford Centre for Magnetic Resonance, University of Oxford, Oxford, United Kingdom, ⁵Department of Radiology, The Churchill Hospital, Oxford University Hospitals NHS Trust, Oxford, United Kingdom, ⁶The MR Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark

We describe the design of a flexible coil array tuned optimally for ¹³C MRI at 3T (32.1 MHz), but with the coil coupling coefficients matched to be nearly identical at the ¹³C and ²³Na (33.8 MHz) frequencies. In this way, the array provides the means to obtain accurate sensitivity profiles for hyperpolarized ¹³C imaging from the high ²³Na naturally present in biological tissue. We show the feasibility of this approach, and compare the performance to other ¹³C coils, showing that the ¹³C SNR provided by this array is not compromised despite the modification to equalize the ¹³C and ²³Na profiles.

Jabrane Karkouri¹, Saba Shirvani¹, Tiger Zhang¹, Dennis Klomp², Martijn Lunenburg³, Ladislav Valkovic⁴, and Christopher T. Rodgers^1
1Wolfson Brain Imaging Center, University of Cambridge, Cambridge, United Kingdom, ²Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ³Tesla Dynamic Coils, Zaltbommel, Netherlands, ⁴Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, United Kingdom

We evaluated the performance of two RF coil configurations for ultra-high field (7T) 31P-MRS applications in the body. We tested: (A) a dipole Tx/Rx + loop Rx coil vs (B) a quadrature dual-loop Tx/Rx coil. We assessed their relative performance by EM modelling simulations and through phantom and in vivo cardiac scans. Both simulations and experimental verifications indicate that there is notable improvement in terms of B1+ efficiency for the dipole+loop combination compared to quadrature loops. We extrapolate these preliminary findings to predict the performance of the dipole+loop combination if driven at 35kW total like our previous whole-body birdcage coil.

Wen-Ju Pan¹, Lei Zhou¹, Gloria Perrin Clavijo¹, Vahid Khalilzad Sharghi¹, and Shella Keilholz^1
1Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA, United States

Single loop coil was optimized in 3D shape to fitting rodent bran geometry and designed in slim and large center opening to meet the requirement of simultaneous fMRI and optical imaging. Relative to conventional 2D flat loop, the proposed 3D design may allow setting a loop coil closer to rat cerebral hemispheres and save more overhead space for optical imaging configuration than a 2D flat coil while keeping B1 perpendicular to B0. Our 3D-shape modification exhibited significant improvement in overall SNR and signal homogeneity especially in cortical areas and center brain in T2-weighted images, EPI and field maps.

Tomohisa Okada¹, Shinya Handa², Bill Ding², Shin-ichi Urayama¹, Koji Fujimoto¹, Atsushi Shima³, Takashi Ayaki⁴, Nobukatsu Sawamoto³, Ryosuke Takahashi⁴, Hirotaka Onoe¹, Tadashi Isa¹, and Labros Petropoulos^2
1Human Brain Research Center, Kyoto University, Kyoto, Japan, ²Quality Electrodynamics, Mayfield Village, OH, United States, ³Department of Human Health Sciences, Kyoto University, Kyoto, Japan, ⁴Department of Neurology, Kyoto University, Kyoto, Japan

MR imaging is frequently correlated to histopathology of specimen, and their high-resolution imaging is required. However, it is not usually feasible using the whole-body human MR scanner. We implemented inductively coupled small diameter coils insertable to the knee coil at 7T without modification of the coil interface. Up to isotropic 50 μm imaging was successfully conducted, and fine details of the specimen could be visualized using the same sequence for in vivo scans. The proposed coils are easy to use and will facilitate investigation of image-histopathology correlation.

Kuan-Hung Cho¹, Po-Hsun He¹, Hsuan-Han Chiang¹, Ming-Jye Chen¹, Ezequiel Farrher², Nadim Jon Shah^2,3, Chang-Hoon Choi², and Li-Wei Kuo^1,4
1Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Miaoli County, Taiwan, ²Institute of Neuroscience and Medicine – 4, Forschungszentrum Juelich, Juelich, Germany, ³Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany, ⁴Institute of Medical Device and Imaging, National Taiwan University College of Medicine, Taipei, Taiwan

For mouse brain imaging, determining the size of a loop coil is a trade-off between SNR and imaging coverage. Here, we propose a multi-purpose coil arrangement incorporating a small loop coil and a position-adjustable add-on saddle coil to enhance the imaging coverage of anatomical images and improve the SNR in the regions distant to the surface coil. The result shows the imaging coverage can be adjustable for targeting different brain regions and demonstrated this design concept in mouse brain imaging experiments.

Yuto Murakami¹ and Yasuhiko Terada^1
1University of Tsukuba, Tsukuba, Japan

A double helix dipole (DHD) coil, consisting of two tilted solenoid coils, exhibits the high signal-to-noise ratio (SNR) close to that of an equivalent solenoid whose SNR is almost three times larger than a saddle coil. However, its application to high-field MRI is challenging because of the high inductance. Here, we proposed a new DHD coil design with division capacitors that enables high-field MRI application. As proof-of-concept, we designed a 6-turn DHD coil for MR microimaging of a chemically-fixed human embryo specimen at 7T, and showed that the proposed DHD has nearly twice the SNR of an equivalent saddle coil.

Sri Kirthi Kandala¹ and SungMin Sohn^2
1Biomedical Engineering, Arizona State Universirty, Tempe, AZ, United States, ²Biomedical engineering, Arizona State University, Tempe, AZ, United States

Impedance matching of RF coils during MR imaging is crucial to improve SNR and would enhance power transfer efficiency for transmit coil reducing wastage of RF power. This work focuses on presenting a stand-alone system with wireless Automatic Tuning and Matching system (ATM) for transmit (Tx)-only and receive (Rx)-only coils separately. We present separate Tx-only and Rx-only coils with high power and low power ATMs respectively along with a self-triggering circuit for Rx coil decoupling while high power Tx signal is active.

Daniel Papp¹, Urs Schüffelgen², Mo Shahdloo², Sebastian W Rieger^1,3, Aaron T Hess⁴, Matthew Rushworth², and Stuart Clare^1
1Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom, ²Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom, ³Wellcome Centre for Integrative Neuroimaging, OHBA, Department of Psychiatry, University of Oxford, Oxford, United Kingdom, ⁴British Heart Foundation Centre of Research Excellence, Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom

A 15-channel array coil has been developed for our centre by a coil manufacturer for the purposes of awake behaving macaque fMRI. Here, we evaluated the imaging performance in vivo and on phantoms. Compared to a 4 channel flexible coil, we found significant improvements in SNR and tSNR both in vivo and in phantom studies. Furthermore, we demonstrate the feasibility of multiband and in-plane accelerated acquisitions, up to a multiband factor of 6 with in-plane acceleration of 2.