Improving RF Shimming Via Non-Linear Sub-Image Combination

Ulrich Katscher¹, Peter Vernickel¹, Kay Nehrke¹, Ingmar Graesslin¹

RF shimming is able to overcome B1 inhomogeneities at high main fields via optimizing the drive weights of multiple transmit channels. However, due to the limited degrees of freedom in this approach, residual B1 inhomogeneities might occur for particular anatomies. This study tries to mitigate residual B1 inhomogeneities by a suitable, non-linear combination of images obtained from different sub-images. The sub-images have been acquired using different drive weights of the transmit channels, leading to complementary inhomogeneities in the different sub-images. The subsequent combination of the sub-images can be optimized with respect to constant total B1 and constant image contrast.