A second-order and slice-specific linear shimming technique to improve spinal cord fMRI

Tsivaka, D., Williams, S. C. R., Medina, Sonia, Kowalczyk, O. S., Brooks, J. C. W. ORCID: https://orcid.org/0000-0003-3335-6209, Howard, M. A., Lythgoe, D. J. and Tsougos, I. (2023) A second-order and slice-specific linear shimming technique to improve spinal cord fMRI. Magnetic Resonance Imaging, 102. pp. 151-163. ISSN 0730-725X

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Purpose: To develop a second-order and slice-specific linear shimming technique and investigate its efficiency in the mitigation of signal loss and distortions, and the increase of temporal signal-to-noise ratio (tSNR) within the spinal cord during functional Magnetic Resonance Imaging (fMRI) of the human cervical spinal cord. Methods: All scans were performed on a General Electric Discovery MR750 3 T scanner, using a head, neck and spine coil and a neurovascular array. To improve B0 homogeneity, a field map was acquired, and second-order shims (SOS) were optimized over manually defined regions of interest (ROIs). Signal loss from dephasing by susceptibility-induced gradients was reduced by optimizing slice-specific x-, y- and z-shims to maximize signal within the spinal cord. Spectral-spatial excitation pulses were used in both the slice-specific linear shimming calibration scan and fMRI acquisitions. The shimming technique's efficiency was initially tested on eight healthy volunteers by comparing tSNR between images acquired with the manufacturer's standard linear shimming and with our SOS and xyz-shimming technique. Subsequently, using an increased spatial resolution as needed for fMRI of the spinal cord, tSNR measurements were performed on resting-state fMRI images from 14 healthy participants. Results: Spinal fMRI images acquired with only the standard linear shimming suffered from severe signal loss below the C5 vertebral level. The developed shimming technique compensated for this loss especially at levels C6 and C7, while tSNR was significantly higher at all vertebral levels with SOS and xyz-shimming than without it. Conclusion: A comprehensive shimming approach which includes the use of spectral-spatial excitation pulses along with both second-order and slice-specific linear shim optimization reduces regional signal loss and increases tSNR along the c-spine (C3-C7), improving the ability to record functional signals from the human spinal cord.

Item Type: Article
Additional Information: Funding Information: The authors wish to thank GE Healthcare and the National Institute for Health Research (NIHR), Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College London, for their continued support of our neuroimaging research. MAH, JCWB, OSK, SMH and SCRW are also supported by a Medical Research Council Experimental Medicine Challenge Grant ( MR/N026969/1 ). Publisher Copyright: © 2023 Elsevier Inc.
Uncontrolled Keywords: field-mapping,fmri,linear shimming,second-order shimming,spinal cord,biophysics,biomedical engineering,radiology nuclear medicine and imaging,sdg 3 - good health and well-being ,/dk/atira/pure/subjectarea/asjc/1300/1304
Faculty \ School: Faculty of Social Sciences > School of Psychology
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Depositing User: LivePure Connector
Date Deposited: 04 Mar 2024 18:26
Last Modified: 04 Mar 2024 18:26
URI: https://ueaeprints.uea.ac.uk/id/eprint/94442
DOI: 10.1016/j.mri.2023.06.012

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