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Abstract #0642

Local SAR Reduction in Multi-Slice PTx Via SAR Hopping Between Excitations

Bastien Guerin1, Elar Adalsteinsson2, 3, Lawrence L. Wald1, 3

1Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, United States; 2Dept of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States; 3Harvard-MIT Division of Health Sciences Technology, Cambridge, MA, United States

The time scale of RF transmission being much smaller than the time scale of temperature changes, only SAR averaged over several pulses needs to be constrained, not the SAR of individual pulses. In this work, we propose a multislice excitation strategy using pulses with minimally overlapping SAR distributions and jointly optimized so as to minimize their average local SAR. This strategy is not affected by ghosting since a given slice is always excited by the same pulse. It allows reduction of pulse-averaged local SAR by 35% for RF shimming and pTx arrays with two rows compared to pulses designed independently.