Figure 4.

Comparison of the flip angle distribution for two adjacent channels and RF shimming results (with all eight channels) in triangular coil array (a) and rectangular coil array (b), in different transverse slices along z direction (center and 40mm in either direction). Coil 1 and coil 2 alternate in intensity when moving along z for the triangular array but not for the rectangular array. These additional variations in the B1 profile also affect the RF shimming performance of the triangle array. Compared to the rectangular array, RF shim configurations designed for the central slice in the triangle array perform less well off-center where the triangle coil has fewer effective elements. When shimming on a coronal plane, however, the additional variation in the B1 profiles help to create more uniform solutions.