Improving signal homogeneity of whole-brain DWI at 7T with universal multiband GRAPE pTx pulses

Motivation: Uniform signal homogeneity in whole-brain DWI at ultra-high fields is challenging. PTx pulses optimized with the GRAPE algorithm may enhance $$$B_1$$$ homogeneity and improve robustness to off-resonance effects. Goal(s): To design universal slice-selective pTx pulses with the GRAPE algorithm for multiband-accelerated whole-brain DWI at 7T and evaluate their performance against CP mode pulses. Approach: PTx pulses were optimized with GRAPE and simulated using Bloch simulations, then tested in vivo on a 7T scanner with five different slice orientations. Additionally, slice profiles of all pulses were obtained. Results: GRAPE pulses demonstrated enhanced signal homogeneity, especially in the cerebellum, with robustness to moderate slice tilts. Impact: Universal slice-selective GRAPE pTx pulses in multiband whole-brain DWI at 7T significantly improve signal homogeneity in the brain and signal intensity in the cerebellum, while being robust to moderate slice tilts. This enables their routine use in neuroscientific studies.