Dynamic B0 shimming of the motor cortex and cerebellum with a multicoil shim setup for BOLD fMRI at 9.4T. Issue 5 (11th November 2019)

• Record Type: Journal Article
• Authors: Aghaeifar, Ali; Bause, Jonas; Leks, Edyta; Grodd, Wolfgang; Scheffler, Klaus
• Is Part Of: Magnetic resonance in medicine. Volume 83:Issue 5(2020)
• Page Start: 1730
• Page End: 1740
• Publication Date: 2019-11-11
• Subjects: B0 inhomogeneity -- BOLD signal -- multicoil -- shimming -- temporal SNR -- ultrahigh field; Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.28044
• Languages: English
• ISSNs: 0740-3194

Abstract

Abstract : Purpose: We assessed how improved static magnetic field (B0 ) 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 B0 homogeneity by dynamic slice‐wise shimming. The performance of dynamic B0 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 B0 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 B0 homogeneity leads to higher tSNR and enhances the detection of BOLD signal.