Figure 5.

Ultimate intrinsic average global SAR for excitation of a transverse FOV through the center of a homogeneous sphere as a function of main magnetic field strength, for SAR-optimized RF shimming (top row) and fully parallel transmission (bottom row). Frequency-dependent average in vivo values of sphere electrical properties were used (see Table 1). The size of the modeled sphere increases from the leftmost to the rightmost column. Results are shown for three different concentric homogeneous target excitation profiles, whose radius is indicated in the legend as a fraction of the sphere radius a.