Application of Rotating RF Coil Array in B1 Shimming with Strict Local SAR Constraints

Jin Jin¹, Feng Liu¹, Adnan Trakic¹, Ewald Weber¹, Stuart Crozier²

This work investigated the possibility of using a four-channel mechanically rotating RF coil array (RRFCA) to shim the transmit magnetic fields for high-field MRI, while strictly controlling local specific absorption rate (SAR). Since the numerous available degrees of freedom in both the temporal and the spatial domain are exploited, a notably higher excitation accuracy was achieved compared with the stationary eight-channel phased-array coil. The results of this primarily theoretical study also signify that, since only a low channel count is required, the geometry of RRFCA can be optimised more flexibly to improve field penetration and therefore excitation efficiency and performance.