A Fast Method to Estimate Peak Local SAR under MRI With RF Shimming

Radio frequency (RF) shimming is widely used in magnetic resonance imaging (MRI) to improve the imaging quality by optimizing excitations of RF coil. However, the changes of RF excitations can significantly change the specific absorption rate (SAR) distribution, and thereby, the peak local SAR inside human bodies under MRI. It is important to estimate the peak local SAR for patients under MRI with RF shimming techniques in real time. In this study, a fast method is proposed to estimate the maximum local SAR under RF shimming. Numerical simulations were performed to model the SAR under different excitations of RF shimming, then space averaging filters were designed to estimate the local SAR. Results are compared with IEC standard method, as results suggested, this method is capable of estimating both location and value of mass averaged SAR under different excitation modes.