Impact of Number of Tx Channels for RF Shimming an in vivo Study

Alexander Childs¹, Shaihan J. Malik¹, Declan P. O'Regan¹, Joseph V. Hajnal¹

Multi-channel transmission allows individualised subject specific RF shimming to be used to mitigate B1+ inhomogeneity and improve image signal and contrast uniformity. Using a whole body 3T system with 8 transmit channels, we have performed a systematic study in vivo of RF shim performance in both the pelvis and thighs for coil configurations with 1, 2, 4 or 8 independent channels. As the number of channels was increased, B1+ homogeneity progressively and significantly increased, while total RF power requirements for the same homogeneity systematically decreased. T1w images also showed perceptible progressive improvement with number of channels used for shimming.