At 7T, increased field strength and limited gradient performance results in increased geometric distortions for echo planar imaging. Use of higher order shims and dynamic updating on a slice by slice basis can dramatically reduce the extent of these distortions. This work describes: 1) the theoretical basis for the extension of slice by slice dynamic shim updating for multi-band acquisitions; 2) demonstrates that higher order spherical harmonic shim systems can intrinsically achieve MB=2 imaging with no loss in in-plane homogeneity in comparison to slice by slice shimming (MB=1), and 3) these improvements are easily visualizable in EPI.
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