William A. Grissom1, Laura Sacolick1, Mika W. Vogel1
1GE Global Research,
3D parallel spokes excitation pulses have been proposed for compensating flip angle inhomogeneities induced by inhomogeneous B1+ at high field. While flip angle homogeneity improves with increasing spokes pulse duration and an increasing number of parallel excitation channels, competing desires to limit off-resonance sensitivity and system complexity limit these pulses' effectiveness in practice. We show that nonlinear gradient phase encoding is well-suited to this application and that simultaneous linear and nonlinear phase encoding can significantly improve spokes pulse performance, enabling shorter pulse durations and fewer transmit channels for a desired level of flip angle homogeneity.