3rd order shim for high resolution fMRI at 7T: It hurts more than it helps

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

Publication Details

Journal
Zenodo (CERN European Organization for Nuclear Research)
Published
2025-05-16
DOI
https://doi.org/10.5281/zenodo.15430478
Primary Topic
Enzyme Structure and Function
Type
article
Field-Weighted Citation Impact
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article

3rd order shim for high resolution fMRI at 7T: It hurts more than it helps

Zenodo (CERN European Organization for Nuclear Research)
Enzyme Structure and Function
article

3rd order shim for high resolution fMRI at 7T: It hurts more than it helps

article en

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.

Zenodo (CERN European Organization for Nuclear Research)
Centre National de la Recherche Scientifique (FR), National Institutes of Health (US), University of Bonn (DE), University of Illinois Urbana-Champaign (US), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), German Center for Neurodegenerative Diseases (DE), Maastricht University (NL), CEA Paris-Saclay (FR)
Openalex Percentile: Top 63%
Enzyme Structure and Function
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3rd order shim for high resolution fMRI at 7T: It hurts more than it helps · Zenodo (CERN European Organization for Nuclear Research) (2025) | TGRS Research Map | TGRS