Relaxation compensation in preparation-based cardiac B1+ mapping

Motivation: Cardiac MR at high field strengths offers increased SNR, but suffers from RF field inhomogeneities. Preparation-based B1+ mapping techniques are promising for robust mapping but are susceptible to confounders. Goal(s): Zero-degree hyperbolic secant (HS) pulses are evaluated to mitigate bias due to T1ρ relaxation in preparation-based B1+ mapping in the heart. Approach: A zero-degree HS pulse is introduced as a baseline measurement and tested in simulations and phantoms. B1+ map quality is evaluated in vivo. Results: Thorough compensation is achieved with confounder correction in simulations and reduced error slope in phantom. Preparation-based B1+ mapping achieves superior in vivo mapping quality compared with DREAM. Impact: Confounder-corrected preparation-based B1+ mapping enables robust B1+ map quality in the human heart. Confounder correction can help to further reduce bias, which may be particularly important for assessing B1+ trends across tissue boundaries with different T1rho times.