Dynamic pTx pulse design with accelerated B1+-mapping for cardiac imaging at 7T

Motivation: Subject-specific pTx methods can counteract excitation inhomogeneities in UHF body imaging, but require lengthy calibration times. Calibrationless universal approaches exist but yield reduced homogeneity for similar SAR levels. Goal(s): Our aim was to evaluate the possibility of shortening the calibration time by accelerating the B1+-mapping process. Approach: For 35 heart subjects, tailored pTx pulses were designed on B1+-maps with different undersampling and their performance was compared to universal approaches regarding flip angle homogeneity and SAR. Results: Tailored pulses designed on accelerated, undersampled B1+-maps (TA=30s) result in improved homogeneity compared to universal pulses or in a roughly 2.5-fold reduction of SAR at comparable homogeneity. Impact: Subject-specific pTx pulses optimized on accelerated, undersampled B1+-maps allow for improved homogeneity or reduced SAR compared to universal pulses. Reduced SAR could benefit body imaging at 7T, since SAR limitations often prevent the optimal choice of acquisition parameters at UHF.