Fast B1 Mapping using a STEAM-Based Bloch-Siegert Preparation Pulse

Kay Nehrke¹, Peter Brnert¹

Fast B1-mapping is an essential prerequisite for multi-element transmit applications like e.g. RF-shimming or multi-dimensional RF pulse design. However, the acquisition speed of B1-mapping sequences is typically limited by SAR constraints, relaxation times, or characteristic sequence properties. In this work, a novel STEAM-based preparation sequence is presented, which employs the recently introduced Bloch-Siegert B1-mapping approach. The preparation sequence stores the Bloch-Siegert phase shift along the longitudinal magnetization, which allows the fast readout of the stimulated echo by a subsequent train of small angle pulses. The flexibility and versatility of this concept is demonstrated in experiments on phantoms and in vivo.