Improved EPI at 7T with Dynamic Multi-coil Technique (DYNAMITE) Shimming

INTRODUCTION: Echo-planar imaging (EPI) and its variants form the core of many functional and structural imaging studies. Image quality of these scans deteriorates drastically with increasing B0 inhomogeneities. Although post-processing can correct aspects related to image distortion, the only way to prevent signal dropout is by improved shimming. Commonly, higher-order static spherical harmonic (SH) shims are used to address this issue. Further gains have been reported with dynamic SH shimming, wherein the shim settings are optimized on a per-slice basis and updated during imaging in a slice-specific fashion. Recently, even better results were reported when dynamic shim fields were generated by an array of small individual coils placed around the subjects' head. 3 In this study, we demonstrate that this dynamic multi-coil technique (DYNAMITE) leads to less distortion and reduced signal dropout in EPI of the human brain at 7 Tesla, in comparison with those acquired with SH shims.