@article{30ca762e47cf4cb88183ad4f39bef51d,
title = "B0 concomitant field compensation for MRI systems employing asymmetric transverse gradient coils",
abstract = "Purpose: Imaging gradients result in the generation of concomitant fields, or Maxwell fields, which are of increasing importance at higher gradient amplitudes. These time-varying fields cause additional phase accumulation, which must be compensated for to avoid image artifacts. In the case of gradient systems employing symmetric design, the concomitant fields are well described with second-order spatial variation. Gradient systems employing asymmetric design additionally generate concomitant fields with global (zeroth-order or B0) and linear (first-order) spatial dependence. Methods: This work demonstrates a general solution to eliminate the zeroth-order concomitant field by applying the correct B0 frequency shift in real time to counteract the concomitant fields. Results are demonstrated for phase contrast, spiral, echo-planar imaging (EPI), and fast spin-echo imaging. Results: A global phase offset is reduced in the phase-contrast exam, and blurring is virtually eliminated in spiral images. The bulk image shift in the phase-encode direction is compensated for in EPI, whereas signal loss, ghosting, and blurring are corrected in the fast-spin echo images. Conclusion: A user-transparent method to compensate the zeroth-order concomitant field term by center frequency shifting is proposed and implemented. This solution allows all the existing pulse sequences—both product and research—to be retained without any modifications. Magn Reson Med 79:1538–1544, 2018.",
keywords = "B, asymmetric gradients, frequency shifting, real-time correction",
author = "Weavers, {Paul T.} and Shengzhen Tao and Trzasko, {Joshua D.} and Frigo, {Louis M.} and Yunhong Shu and Frick, {Matthew A.} and Lee, {Seung Kyun} and Foo, {Thomas K.F.} and Bernstein, {Matt A.}",
note = "Funding Information: 1Mayo Clinic Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA. 2Mayo Graduate School, Mayo Clinic, Rochester, Minnesota, USA. 3GE Healthcare, Waukesha, Wisconsin, USA. 4GE Global Research, Niskayuna, New York, USA. 5Center for Neuroscience Imaging Research, IBS, and Dept of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea. Grant sponsor: NIH; Grant number: R01EB010065. Correction added after online publication 21 July 2017. The authors have added reference 19 and updated the Acknowledgment. In accordance with ICMJE guidelines, MAB recused himself from the handling of this paper and all editorial decisions related to it. ST, PTW, JDT, YS, and MAB have filed a patent application related to the described methods. Tom Foo, Lou Frigo, Seung-Kyun Lee, and Paul Weaver are current or former employees of GE Healthcare or GE Global Research. All work was done while Paul Weaver was a Mayo Clinic employee. *Correspondence to: Matt A. Bernstein, PhD, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. E-mail: mbernstein@mayo.edu. Received 10 March 2017; revised 20 May 2017; accepted 23 May 2017 DOI 10.1002/mrm.26790 Published online 21 June 2017 in Wiley Online Library (wileyonlinelibrary.com). Publisher Copyright: {\textcopyright} 2017 International Society for Magnetic Resonance in Medicine Copyright: Copyright 2020 Elsevier B.V., All rights reserved.",
year = "2018",
month = mar,
doi = "10.1002/mrm.26790",
language = "English (US)",
volume = "79",
pages = "1538--1544",
journal = "Magnetic Resonance in Medicine",
issn = "0740-3194",
publisher = "John Wiley and Sons Inc.",
number = "3",
}