Design of dynamic kT-point pTx pulses for renal imaging at 7T

Motivation: In ultra-high field MRI, transmit magnetic field (B1+) inhomogeneities are affecting kidney imaging. Goal(s): Our goal was evaluate dynamic kT-point pulses for homogenous excitation in bilateral renal imaging. Approach: Channel-wise B1+ maps of the kidneys were acquired for 15 subjects. Universal and individual kT-point pulses with different number of subpulses were calculated and evaluated. For one subject anatomical images were acquired with phase shims and dynamic kT-point pulses. Results: While fixed-phase shims still suffer from flip-angle inhomogeneity, universal and subject-specific dynamic pulses with non-selective 5kT-point trajectories improves flip-angle homogeneity in the kidney and enable imaging with homogeneous excitation. Impact: Our study evaluated universal and subject-specific kT-point pulses for kidney MRI at 7T. kT-point pulses substantially improve flip-angle homogeneity and universal pulses enable calibration-free imaging at ultra-high field, promising advances in high-resolution renal imaging.