Current high resolution, whole brain diffusion MRI protocol at 7T
for the Human Connectome Project uses linear phase multiband (MB) refocusing pulses
that have duration longer than 10 ms. Recent studies show that shorter duration
can be obtained by designing nonlinear phase MB refocusing pulses. In this
study, we designed root-flipped MB and hyperbolic secant (HS1) based MB
refocusing pulses and investigated how the variable rate selective excitation
(VERSE) principle can be used to further reduce the pulse duration. Our results
suggest that both root-flipped and HS1 based MB refocusing pulses can be
shortened by VERSE.
