Figure 8.

Summary of global and dynamic MC shimming experiments on four volunteers. (a) Representative slices of acquired ΔB₀ maps from each volunteer for the 2SH baseline, global MC shim, and dynamic MC shim cases. (Axial, sagittal, and coronal slices of the ΔB₀ maps for Subject 3 are shown in Supporting Information Figure S4). While MC shimming reduces the size of the ΔB₀ “hotspot” in the frontal lobes, the coil basis set does not have sufficiently high spatial order to match the shape of the hotspot exactly. The compensating shim fields thus extend past the hotspot and reduce B₀ homogeneity toward the middle of the head (purple arrow). (b) The standard deviation in each slice (𝜎^SL) is plotted for each shimming case. (c) The overall histogram of ΔB₀ over the whole brain for each subject along with summary of 𝜎^WB in Hz for each subject. A zoomed inset shows the improvements in outlier voxels achieved using MC shimming.