Fig. 5.

Ideal surface current patterns associated with the best possible SNR for a voxel position intermediate between the center and the surface of the sphere at 1.5 T. On the left-hand side of the top row, current patterns are plotted for an arbitrary time point on a two-dimensional “unwrapped” view of the spherical surface, whereas on the right-hand side, a schematic representation shows how the current patterns evolve in time. In the middle and bottom rows, three-dimensional representations and explanatory diagrams of the current patterns are shown for four time points, respectively. Ideal currents patterns are localized near the voxel of interest and alternate between distributed single-loop and distributed figure-eight, or butterfly, configurations every Δωt = π/2, inverting direction every Δωt = π.