Gregor Adriany¹, Scott Schillak², Matt Waks², Brandon Tramm², Andrea Grant¹, Essa Yacoub¹, Tommy Vaughan¹, Cheryl Olman¹, Sebatian Schmitter¹, and Kamil Ugurbil^1
1Medical School, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ²Virtumed LLC, MN, United States

Multi-channel transmit arrays are essential at ultra hifh fields (UHF) to gain B1+-field control and to support parallel transmission. We combined a dedicated 16 channel transmit array with a 32 channel receive only array in a tightfitting modular coil housing. Results demonstrated excellent coil separation , whole brain coverage and SNR. The achievable homogeneity is significantly improved compared to a 1TX32RX whole brain coil (Nova Medical, Wilmington,MA,USA). The major advantage of the presented coil is increased pTX capability due to a dual row Tx design and significantly improved task presentation.

Kyle M Gilbert¹, Joseph S Gati¹, Esther Kho^1,2, L Martyn Klassen¹, Peter Zeman¹, and Ravi S Menon^1
1The University of Western Ontario, London, Ontario, Canada, ²University of Groningen, Groningen, Netherlands

An 8-channel transmit coil and 32-channel receive coil were developed for use in a 7T head-only scanner. The limited radial space allotted for an RF coil in a head-only scanner presents design challenges that can affect coil performance. Further complexity arises when designing the coil to be practical for patient studies and routine scanning. These challenges and their solutions are discussed in this study, along with an evaluation of the coil performance.

Guillaume Donati¹, Ozlem Ipek², Eulalia Serés Roig¹, and Rolf Gruetter^1,3
1Laboratory of Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, ²Centre d'Imagerie Biomédicale, École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, ³Department of Radiology, Universities of Lausanne and Geneva, Lausanne, Geneva, Switzerland

The main drawback of ¹³C-MRS is the low sensitivity, which makes ¹³C detection difficult. In addition, the ¹³C-¹H hetero-nuclear J coupling necessitates double-tuned ¹³C-¹H coils for proton decoupling during ¹³C signal acquisition. Array coils provide a high sensitivity over a large field-of-view. In this study, a four channel ¹³C-four channel ¹H transceiver array coil for direct ¹³C-MRS in human brain at 7T was built. EM simulations show a fourfold improvement of B₁⁺/√SAR_10g,max compared to a linear ¹³C-quadrature ¹H coil. ¹H-decoupled ¹³C MRS spectra were acquired in vitro, demonstrating the feasibility of an eight channel double-tuned transceiver ¹³C-¹H array at 7T.

Pu-Yeh Wu¹, Ying-Hua Chu¹, Aapo Nummenmaa², Thomas Witzel², Shang-Yueh Tsai³, Wen-Jui Kuo⁴, and Fa-Hsuan Lin^1,2
1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, ²Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ³Institute of Applied Physics, National Chengchi University, Taipei, Taiwan, ⁴Institute of Neuroscience, National Yang Ming University, Taipei, Taiwan

A slim TMS-compatible MRI 10-channel RF coil array was developed. The coil array was 2 mm thick to maximize TMS efficacy and positioning freedom. Empirical data show that the average SNR of TMS-compatible coil array is 44% better than the commercial 32-channel array within the 5 cm depth. This TMS-compatible RF coil array is expected to offer both anatomical images and functional MRI signal induced by TMS with high sensitivity.

Bei Zhang¹, Priti Balchandani¹, Zahi A. Fayad¹, Joo-won Kim¹, Christopher Cannistraci¹, Bernd Stoeckel², and Junqian Xu^1
1Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States, ²Siemens Medical Solution, New York, New York, United States

A 22 channel wrap-around coil array was built for 7T cervical spinal cord imaging. The coil consists of four transmit-receive (Tx/Rx) elements and eighteen receive-only (Rx) elements. Two of the four Tx/Rx elements are anterior and the other two are posterior to the subject. The eighteen Rx elements, of which six are anterior and twelve are posterior to the subject, surround the Tx/Rx elements. All the coils follow the contour of the body to maximize SNR. Both simulation and experiments show high transmit efficiency with the wrap-around design and excellent SNR for high-resolution cervical spinal cord imaging at 7T.

Qi Duan¹, Govind Nair², Natalia Gudino¹, Jacco A. de Zwart¹, Peter van Gelderen¹, Joseph Murphy-Boesch¹, Daniel S. Reich², Jeff H. Duyn¹, and Hellmut Merkle^1
1Laboratory of Functional and Molecular Imaging, NINDS, National Institutes of Health, Bethesda, MD, United States, ²Division of Neuroimmunology and Neurovirology, NINDS, National Institutes of Health, Bethesda, MD, United States

To date, loop-based arrays are still the prevailing design for 7 T spine imaging. In this work, a prototype that combines loops for signal reception with electric dipole antennae for transmit is presented. It aims to circumvent the dilemma for optimizing loop arrays at 7 T caused by the conflicting extended field-of-view and short wavelength. In comparison with a previous loop-based design, the new array has simpler cabling and higher transmit efficiency, even after correcting for slightly elevated SAR deposition. The reduced power need could be exploited to increase resolution or acquisition speed more than twofold.

Karthik Lakshmanan^1,2, Martijn Cloos^1,2, Ryan Brown^1,2, Timothy Shepherd^3,4, and Graham C Wiggins^1,2
1The Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, Newyork, NY, United States, ²The Center for Advanced Imaging Innovation and Research (CAI2R),Department of Radiology, New York University School of Medicine, Newyork, NY, United States, ³Radiology, NYU Langone Medical Center, NY, United States, ⁴The Center for Advanced Imaging Innovation and Research (CAI2R),Department of Radiology, New York University School of Medicine, NY, United States

A loop coil with a highly non-uniform current distribution can capture loop like and dipole like fields. This “loopole” element provides the opportunity to tailor both the orientation and the intensity of its asymmetric current to achieve improved B1+ efficiency or SNR. In this work the feasibility of using loopole elements as building blocks to create transceiver arrays is explored. A novel split four-element loopole array with two anterior and two posterior elements was modeled and constructed. The array was used to image the human spine at 7.0T. The loopole array exhibited substantial performance improvements over published spine array designs.

Yukio Kaneko¹, Yoshihisa Soutome^1,2, Hideta Habara^1,2, Yoshitaka Bito², and Hisaaki Ochi^1
1Central Research Laboratory, Hitachi Ltd., Kokubunji, Tokyo, Japan, ²Hitachi Medical Corporation, Kashiwa, Chiba, Japan

The B1 inhomogeneity in a human body increases as the strength of a static magnetic field increases. Various methods to reduce the B1 inhomogeneity have been developed. However, B1 inhomogeneity in the z-direction still remains in lumbar spine (L-spine) imaging. Our previous study showed that a �gB1-control receive array coil (BRAC)�h and �gB1 rectifying fin (BRF)�h can control the B1 field locally. In this study, BRAC and BRF were designed in an FDTD simulation, and the B1 field and local SAR in a human model were calculated. BRAC and BRF were confirmed to reduce B1 inhomogeneity in the L-spine imaging.

Stephan Orzada¹, Andreas K. Bitz², Marcel Gratz^1,3, Sören Johst¹, Maximilian N. Völker¹, Oliver Kraff¹, Dominik Beyer¹, Tristan Mathiebe¹, Ashraf Abuelhaija⁴, Klaus Solbach⁴, and Mark E. Ladd^2
1Erwin L. Hahn Institute for MRI, Essen, NRW, Germany, ²Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany,³High-field and Hybrid MR Imaging, University Clinic Essen, Essen, Germany, ⁴RF Technology, University Duisburg-Essen, Duisburg, Germany

In this work we present an 8-channel Tx/Rx array for 7 Tesla whole-body imaging which is situated between the inner bore liner and the gradient coil similar to the body coils in standard low-field systems. The array is compared to a close-fitting array of similar elements, and first images of a human volunteer are presented. While transmit efficiency and SNR are reduced in comparison to a close-fitting array, a larger field-of-view in the z-direction is achieved.

Ingmar J. Voogt¹, Dennis W.J. Klomp¹, Hans Hoogduin¹, Mariska P. Luttje¹, Peter R. Luijten¹, Cornelis A.T. van den Berg¹, and Alexander J.E. Raaijmakers^1
1Imaging Division, UMC Utrecht, Utrecht, Utrecht, Netherlands

We developed an 8-element transceiver fractionated dipole array, combined with a detunable 16-element receive-only loop coil array and evaluated it by prostate imaging on six volunteers (BMI 22-32.8). Reflection and coupling levels are low for all investigated subjects. B1+ amplitude in the prostate (after B1 shimming) ranges from 10 ìT (BMI 32.8) to 15.4 ìT (BMI 22). T2w prostate images are of good quality. The SNR of this design is better than for a design with antennas only (27 vs. 22). The good imaging performance with extended acceleration potential make this array an attractive design for body imaging applications.