Reproducible B0 shim matrix calibration at 7T and dynamic range analysis of spherical harmonics for residual compensation

Motivation: Adequate B0 shimming of deep brain regions at 7T using 3rd order shims. Goal(s): Reproduce B0 shim matrix calibration after hardware replacement and estimate possible compensation of residual fields in vivo. Approach: Calibration matrix of the 3rd order B0 shimming system was measured after replacement of the gradient coil. Results were compared with previous calibration. Whole-brain and ROI-specific spherical harmonic decompositions of B0 maps were performed after optimized whole-brain shimming. Results: Shimming calibration matrices could be reproduced with high accuracy on the new hardware. Residual B0 inhomogeneity could potentially be improved with existing shimming hardware. Impact: B0 shimmming calibration matrix is well reproducible on a 7T system equipped with 3rd order shim coils using single and multi-channel receiver coil configurations. Residual B0 inhomogeneity after optimized whole-brain shimming could be potentially improved using available shimming hardware.