Dynamic B₀ shimming for multiband imaging using high order spherical harmonic shims.

ABSTRACT:

Purpose

To describe and implement a strategy for dynamic slice-by-slice and multiband B₀ shimming using spherical harmonic shims in the human brain at 7T.

Theory

For thin axial slices, spherical harmonic shims can be divided into pairs of shims (z-degenerate and non-z-degenerate) that are spatially degenerate, such that only ½ of the shims (non-z-degenerate) are required for single slice optimizations. However, when combined, the pairs of shims can be used to simultaneously generate the same in-plane symmetries but with different amplitudes as a function of their z location. This enables multiband shimming equivalent to that achievable by single slice-by-slice optimization.

Methods

All data were acquired at 7T using a spherical harmonic shim insert enabling

SUBMITTER: Hetherington HP 

PROVIDER: S-EPMC8098050 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature