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Dynamic B 0 shimming of the motor cortex and cerebellum with a multicoil shim setup for BOLD fMRI at 9.4T
Author(s) -
Aghaeifar Ali,
Bause Jonas,
Leks Edyta,
Grodd Wolfgang,
Scheffler Klaus
Publication year - 2020
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.28044
Subject(s) - shim (computing) , voxel , physics , motor cortex , computer science , homogeneity (statistics) , nuclear magnetic resonance , cerebellum , neuroscience , artificial intelligence , medicine , psychology , stimulation , machine learning , erectile dysfunction
Purpose We assessed how improved static magnetic field (B 0 ) homogeneity with a dynamic multicoil shimming can influence the blood oxygen level dependent (BOLD) contrast to noise when echo planar imaging (EPI) sequence is used for a motor task functional MRI study. We showed that a multicoil shim setup can be a proper choice for dynamic shimming of 2 spatially distant areas with different inhomogeneity distributions. Methods A 16‐channel multicoil shim setup is used to provide improved B 0 homogeneity by dynamic slice‐wise shimming. The performance of dynamic B 0 shimming was investigated in 2 distinct brain regions, the motor cortex and the cerebellum, in the same experiment during a finger‐tapping task. Temporal SNR (tSNR), geometric distortion of the EPIs, and results of an analysis with a general linear model before and after shimming with the multicoil were compared. Results Reduced B 0 deviation by 30% and 52% in the cerebellum and motor cortex, respectively, resulted in higher tSNR and a reduction of distortions in the EPI. Statistical analysis applied to the EPIs showed higher t values and increased number of voxels above significance threshold when shimming with the multicoil setup. Conclusions Improved B 0 homogeneity leads to higher tSNR and enhances the detection of BOLD signal.