Large tip-angle, motion robust pulse design for parallel transmission at 7T using composite B1 distributions

Parallel-transmit (pTx) pulses can help overcome B1 inhomogeneity at ultra-high field, however their performance is sensitive to geometry, orientation and composition of the coil load. Head motion in pTx effectively alters the load, damaging pulse performance and reintroducing artificial contrast to images. Here, we introduce a versatile method to reduce in-plane motion sensitivity of large tip-angle, parallel transmit pulses by designing pulses based on weighted-average B1-distributions. These include B1-distributions from multiple head positions to effectively expand the area over which the pulse can function. Error in resulting inversion profiles is reliably reduced following most in-plane translations and rotations, demonstrating motion-robustness.