Motivation: B1+ maps are crucial for MRI applications at high field strengths, but existing methods are often limited by long acquisition times, high power requirements, or T1 saturation effects. Goal(s): To develop a rapid, low-power, phase-based B1+ mapping method using composite pulses. Approach: A phase-based method is proposed that uses optimized composite pulses to manipulate magnetization and achieve high phase accrual using low power and a 32-channel head coil. Results: Simulations, phantom, and in-vivo studies validate the proposed method. It enables rapid B1+ mapping with 4 mm isotropic resolution for the entire 3D brain in 10 seconds at high field strengths. Impact: The proposed rapid, low-power B1+ mapping method reduces acquisition time and SAR. This improvement enhances its utility in clinical and research settings. Future work aims to extend its application to 7T for pTx applications.
Santoro et al. (2025) studied this question.