The potential value of ultrahigh field (UHF) magnetic resonance imaging (MRI) and spectroscopy to biomedical research and in clinical applications drives the development of technologies to overcome its many challenges. The increased difficulties of imaging the human torso compared with the head include its overall size, the dimensions and location of its anatomic targets, the increased prevalence and magnitude of physiologic effects, the limited availability of tailored RF coils, and the necessary transmit chain hardware. Tackling these issues involves addressing notoriously inhomogeneous transmit B1 (B1+) fields, limitations in peak B1+, larger spatial variations of the static magnetic field B0, and patient safety issues related to implants and local RF power deposition. However, as research institutions and vendors continue to innovate, the potential gains are beginning to be realized. Solutions overcoming the unique challenges associated with imaging the human torso are reviewed as are current studies capitalizing on the benefits of UHF in several anatomies and applications. As the field progresses, strategies associated with the RF system architecture, calibration methods, RF pulse optimization, and power monitoring need to be further integrated into the MRI systems making what are currently complex processes more streamlined. Meanwhile, the UHF MRI community must seize the opportunity to build upon what have been so far proof of principle and feasibility studies and begin to further explore the true impact in both research and the clinic.
Bibliographical noteFunding Information:
From the Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN. Received for publication February 9, 2019; accepted March 12, 2019. Address correspondence to Gregory J. Metzger, PhD, Center for Magnetic Reso-nance Research, University of Minnesota Medical School, 2021 6th Street SE, Minneapolis, MN 55455 (e-mail: firstname.lastname@example.org). Relevant funding from the author’s institution, which supported some of the presented results, originated from NCI R01 CA155268, WM Keck Foundation, NIBIB P41 EB015894, S10 RR029672, S10 RR029672 and NIBIB P41 EB0227061. Authors Erturk and Metzger are co-authors on a patent of the 16LD RF coil. This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. Copyright © 2019 The Author(s). Published by Wolters Kluwer Health, Inc. DOI: 10.1097/RMR.0000000000000202
© 2019 Wolters Kluwer Health, Inc. All rights reserved.
- 7 Tesla
- RF coils
- RF shimming
- body imaging
- parallel transmit
- ultrahigh field