Improved Phase-Based Adiabatic B1 Mapping

Franciszek Hennel¹, Sascha Khler¹

A method for the mapping of the radio-frequency transmission field is proposed that derives B1 values from the phase of the signal. The sequence consists of a block pulse to produce a B1-dependent nutation, followed by an inverse adiabatic half passage (IAFP) that converts the nutation phase to signal phase. Two ways to compensate the undesired dephasing caused by the IAFP are proposed: a rewinder RF pulse, or a matched adiabatic echo. The method provides an increased dynamic range compared to known phase-based B1-mapping sequences.