Multi-echo Bloch–Siegert shift method for simultaneous B1 magnitude and phase mapping

Motivation: Requirement of separate magnitude and phase imaging for complex B1 mapping slows down electrical property tomography. Goal(s): Our goal was to develop a novel sequence to obtain the complex B1 field in a single acquisition. Approach: The Bloch-Siegert shift B1 mapping sequence was combined with the multi-echo gradient echo acquisition. The B1 magnitude and phase were separated by a voxel-wise linear regression. The developed sequence was implemented in a 7 T scanner and validated by phantom experiments. Results: The B1 maps acquired by the developed sequence were consistent with those of conventional methods that obtain B1 magnitude and phase separately. Impact: The developed sequence accelerates complex B1 mapping by enabling simultaneous acquisition of the magnitude and phase of the B1 field with equivalent accuracy to conventional methods in which these images are obtained separately, facilitating electrical property tomography.