Accurate B1 measurement is important in many MR related applications. In this study, we proposed and optimized a phase-sensitive approach for B1 mapping that relies on a multi-gradient-echo sequence with two successive orthogonal RF pulses used for signal excitation. We also proposed optimized methods for combining multi-channel data, allowing for optimal parameters’ estimation. The method was validated on phantoms and tested on human participants. By applying this method on SMART (Simultaneous Multi-Angular Relaxometry of Tissue) MRI, we reaffirmed the importance of the B1 correction for quantifying biological tissues relaxation and magnetization transfer parameters.