3rd order shim for high resolution fMRI at 7T: It hurts more than it helps
Year: 2025
Type: conference-paper
Abstract: Synopsis: Motivation: 3rd order B0-shimming at high resolution 7T fMRI can mitigate geometric distortions. But the corresponding shim coils can induce field perturbations when mechanical resonances are excited (Boulant 2024). Goal: We aim to investigate the advantages and disadvantages of 3rd order shimming on high resolution fMRI across scanners and sequences. Approach: We compared EPI artifacts (Fuzzy Ripples) and geometric distortions with and without 3rd order shims in N=15 scans. Results: We find that for high-resolution fMRI protocols, it is best to conduct experiments without 3rd order shims. Shims should be physically disconnected. Impact: The results presented here inform the UHF-fMRI community about a simple trick to improve the data quality: disconnecting 3rd order shim coils.
Institutions: National Institutes of Health, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Building large instruments for neuroimaging: from population imaging to ultra-high magnetic fields, German Center for Neurodegenerative Diseases, University of Illinois Urbana-Champaign, Maastricht University
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: green
Funder: European Commission
OpenAlex ID: W6930854910
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