FIGURE 6.

Needle shim performance at arbitrary orientations. A, A subsample of the −90 to +90 degree range of angles evaluated for shim performance. B, Fieldmap SDs without and with shimming for the angles in (A). C, Total volume of voxels around the needle with signal fraction <50% of maximum signal (estimated assuming 0 field gradient across a voxel) without and with shimming. D, Current demands in the two coils for the same angles. Results from the complete set of 2197 orientations are presented in two supporting video files, Supporting Information Videos S1 and S2