RF shimming usually aims at uniform transmit field. For 7T human first-pass myocardial perfusion, maximizing the lowest transmit field strength is beneficial. The shimming optimization cost function corresponding to the lowest strength is not smooth, leading to impractically long shimming calculation if all transmit magnitudes and phases are optimized simultaneously. We evaluate several optimization strategies for static RF shimming for maximizing the lowest transmit field strength within a practical duration, and propose a two-stage method to accelerate in situ shimming calculation. In our experiments, this proposed method consistently found near optimal solutions in less than 10 seconds.
