Universal "MaxTheMin" B1 Shimming: Robust Adiabatic Pulses at Ultra High-field

Synopsis Keywords: adiabatic pulses, UHF MRI, calibration-free B1 shim Motivation: In ultra high-field MRI, achieving complete magnetization inversion using adiabatic pulses is challenging. Goal(s): Develop robust calibration-free adiabatic pulses which fullfil the adiabatic condition throughout the entire brain. Approach: This study investigates a universal “MaxTheMin” B1 shimming technique, ensuring that the adiabatic condition is satisfied for robust pulse performance. By optimizing the lowest B1 level, we attain high inversion efficiency, even in regions where B1 is initially weak. As a practical application, MP2RAGE acquisitions were performed. Results: Simulations and in vivo experiments confirm that “MaxTheMin” B1 shimming enhances pulse efficacy at 7T, making it a valuable tool for imagingat ultra-high fields. Impact: Universal B1 shimming improves adiabatic pulse performance by enhancing inversion efficiency across the brain without increasing scan time or requiring calibration. This advancement paves the way for higher-quality, more reproducible imaging at UHF, expanding its clinical and research applications.