Abstract #2907

Adiabatic B1 Shimming Algorithm for Multiple Channel Transmit at 7T

Priti Balchandani¹, Mohammad Mehdi Khalighi², Scott Sigao Hsieh^1,3, Kawin Setsompop⁴, John Pauly³, Daniel Spielman¹

¹Radiology, Stanford University, Stanford, CA, United States; ²Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States; ³Electrical Engineering, Stanford University, Stanford, CA, United States; ⁴A.A. Martinos Center for Biomedical Imaging, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, United States

Adiabatic B₁ shimming is a hybrid imaging approach which exploits the flexibility offered by multiple transmit channels to ensure the B₁-immunity of adiabatic RF pulses over the entire spatial region of interest. We developed a simulated annealing optimization algorithm to determine the amplitude and phase adjustments to adiabatic RF pulses played on individual transmit channels. The values were chosen to maximize uniformity of the flip angle while limiting RF amplitude and minimizing worst-case SAR. The final shimming algorithm was applied to 2-channel and 8-channel 7T B₁ transmit maps and the resultant values were tested in simulation. Highly uniform flip angles were achieved.