Motivation: The performance of dynamic pTx pulses might be affected by patient motion, especially in the case of long scanning sessions. Goal(s): To examine the actual impact of motion on the flip angle map of a pTx pulse optimized with a fast online customization (FOCUS) strategy. Approach: B0 and multi-channel B1+ maps were acquired at multiple head positions, and the application of the pulse optimized on the first position was simulated on the subsequent positions. Results: For various ranges of motion measured in this study, FOCUS pTx pulses are demonstrated to be robust to motion occurring after the acquisition of the field maps. Impact: Fast online customized pTx pulses suffer from motion during long scanning sessions, mainly due to changes in B1+ field distribution. However, for motion amplitudes comparable to what was measured, the negative impact on low flip angle non-selective pulses is negligible.
Philippe et al. (Tue,) studied this question.