Priti Balchandani1, Mohammad Mehdi Khalighi2,
Scott Sigao Hsieh1,3, 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.