A self-matched leaky-wave antenna for ultrahigh-field magnetic resonance imaging with low specific absorption rate
Solomakha, G; Svejda, J T; van Leeuwen, C; Rennings, A; Raaijmakers, A J; Glybovski, S; Erni, D
(2021) Nature Communications, volume 12, issue 1
(Article)
Abstract
The technology of magnetic resonance imaging is developing towards higher magnetic fields to improve resolution and contrast. However, whole-body imaging at 7 T or even higher flux densities remains challenging due to wave interference, tissue inhomogeneities, and high RF power deposition. Nowadays, proper RF excitation of a human body in
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prostate and cardiac MRI is only possible to achieve by using phased arrays of antennas attached to the body (so-called surface coils). Due to safety concerns, the design of such coils aims at minimization of the local specific absorption rate (SAR), keeping the highest possible RF signal in the region of interest. Most previously demonstrated approaches were based on resonant structures such as e.g. dipoles, capacitively-loaded loops, TEM-line sections. In this study, we show that there is a better compromise between the transmit signal B1+ and the local SAR using non-resonant surface coils generating a low electric field in the proximity of their conductors. With this aim, we propose and experimentally demonstrate a leaky-wave antenna implemented as a periodically-slotted microstrip transmission line. Due to its non-resonant radiation, it induces only slightly over half the peak local SAR compared to a state-of-the-art dipole antenna but has the same transmit efficiency in prostate imaging at 7 T. Unlike other antennas for MRI, the leaky-wave antenna does not require to be tuned and matched when placed on a body, which makes it easy-to-use in prostate imaging at 7 T MRI.
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Keywords: General Physics and Astronomy, General Chemistry, General Biochemistry,Genetics and Molecular Biology, Research Support, Non-U.S. Gov't, Journal Article
ISSN: 2041-1723
Publisher: Nature Publishing Group
Note: Funding Information: Numerical and experimental studies of the leaky-wave antenna were supported by the Russian Foundation for Basic Research (Grant No. 19-29-10038). Numerical investigation of the different types of antenna elements was supported by the Russian Science Foundation (Project 19-75-10104). This project received funding from the European Union’s Horizon 2020 research innovation program under grant agreement no. 736937. The authors thank Dr. Bart Steensma, Dr. Redha Abdeddaim, Prof. Constantin Simovski, Prof. Stefano Maci, Prof. Chris Collins, Ksenia Lezennikova, Ekaterina Brui and the team of the RF-coils lab at UMC Utrecht for their help and useful discussions. Publisher Copyright: © 2021, The Author(s). Copyright: Copyright 2021 Elsevier B.V., All rights reserved. Funding Information: Numerical and experimental studies of the leaky-wave antenna were supported by the Russian Foundation for Basic Research (Grant No. 19-29-10038). Numerical investigation of the different types of antenna elements was supported by the Russian Science Foundation (Project 19-75-10104). This project received funding from the European Union’s Horizon 2020 research innovation program under grant agreement no. 736937. The authors thank Dr. Bart Steensma, Dr. Redha Abdeddaim, Prof. Constantin Simovski, Prof. Stefano Maci, Prof. Chris Collins, Ksenia Lezennikova, Ekaterina Brui and the team of the RF-coils lab at UMC Utrecht for their help and useful discussions. Publisher Copyright: © 2021, The Author(s).
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