Variations in signal intensity and CNR as a function of flip angle for both single slice and three slice multi-slice acquisitions. Phantom results are shown in red, and are compared to simulation results assuming an ideal slice excitation profile (blue) and those incorporating the actual slice excitation profile (green). (a) Single slice case: the theoretical optimized flip angle for CNR is ~12 degrees, while the phantom study and simulation using the actual slice profile shows an optimal flip angle of ~22 degrees. (b) 3 slices with large inter-slice gap: the CNR was maximized at ~20 degrees with an assumed ideal slice profile, but at ~36 degrees when the actual slice excitation profile was considered. (c) Edge slice results for the 3 slice multi-slice case with no inter-slice gap. (d) Center slice results for the 3 slice multi-slice case with no inter-slice gap.
In all cases, the actual phantom experiment results are in much better agreement with the simulation results that take into consideration the actual slice excitation profile.