Figure 3.

Magnetization simulation. Evolution of transverse magnetization of each isochromat along the z axis and net transverse magnetization from each voxel over 200 sequence repetitions (over 4 sec with TR = 20 msec) is shown for stationary spins (a, b), for steady flow without partial saturation (c, d) and with partial saturation (e, f), and for pulsatile flow without partial saturation (h, i) and with partial saturation (j, k). The flow is in the positive z direction, and the pulsatile flow waveform used is shown in (g). For stationary spins, each spin attains a periodic pseudo-steady state (a); however, the net magnetization of each voxel reaches a steady state (b). Inflow enhancement is greatly reduced by partial saturation for both steady and pulsatile flow (f, k). Slight signal fluctuation from sequence to sequence remains with pulsatile flow (k).