MR Fingerprinting with Dynamic Transmit Shims

Motivation: Transmit-inhomogeneities at ultra-high-field cause realized/effective flip-angles to strongly deviate from the nominal. In quantitative MRI, retrospective correction is possible but leads to spatially varying efficiency for parameter estimation. Parallel-transmit enables spatio-temporal modulation of excitation pulses in MR Fingerprinting (PTX-MRF), potentially improving encoding power by filling in regions of poor precision achieved with a static configuration. Goal(s): Investigate an MRF prototype sequence with temporal modulation of parallel-transmit shims. Approach: We sequentially apply different transmit-shims to modulate realized flip-angles and employ temporal low-rank for reconstruction of singular-component-images. Results: We explored the potential and key requirements for PTX-MRF, showing that parallel-transmit could prove advantageous for MRF. Impact: This work is an explorative step towards addressing transmit-field inhomogeneities at ultra-high-field. Its impact is mainly indicating new directions worthwhile investigating, supported by evidence from phantom experiments.