Qi Duan1, Peter
van Gelderen1, Jeff H. Duyn1
1Advanced
MRI section, LFMI, NINDS, National Institutes of Health, Bethesda, MD, United
States
This abstract investigates fast simultaneous B0/B1+ mapping by Bloch-Siegert shift via lowering the off-resonance frequency of this pulse, as theoretical analysis indicated that the sensitivity of Bloch-Siegert based B1+ mapping can be substantially improved when irradiating closer to resonance. Using optimized irradiation pulse shape and gradient crushers to minimize direct excitation effects, in vivo experiments on human brain at 7T confirmed the improved sensitivity available with this approach operating with peak B1+ much larger than the frequency offset. This improved sensitivity translated into an 80% reduction in B1+ estimation errors, without increasing tissue heating.