GRAPE-based slab-selective universal parallel transmit excitation pulses for whole-brain MRSI at 7 Tesla

Synopsis MotivationWhole-brain MRSI at ultra-high field is hampered by the excitation field inhomogeneity which causes flip angle variations and, consequently, reduced SNR, especially in the cerebellum. GoalsTo improve the flip angle homogeneity and, consequently, increase the SNR of whole-brain ultra-high field MRSI by utilizing universal pTx-pulses. ApproachFrequency-selective universal pulses (UPs) were designed for homogeneous excitation with the GRAPE approach and implemented in a pulse-acquire-based MRSI sequence with concentric-ring readout at 7T. The spectral SNR was estimated with LCModel and compared to CP excitation. ResultGRAPE-UP excitation achieves a mean SNR increase of 23% in the cerebellum.A slight SNR increase was also observed over the whole brain.