B₁ Homogenization and Local SAR Reduction using a B₁-control Receive Array Coil at 3T Proceedings of the 2014 Young Investigator Award

B₁ inhomogeneity in the human body increases as the nuclear magnetic resonance (NMR) frequency increases. Various methods have thus been developed to reduce B₁ inhomogeneity, such as a dielectric pad, a coupling coil, parallel transmit, and radio-frequency (RF) shimming. However, B₁ inhomogeneity still remains in some cases of abdominal imaging. In this study, we developed a B₁-control receive array coil (B-RAC). Unlike the conventional receive array coil, B-RAC reduces B₁ inhomogeneity by using additional PIN diodes to generate an inductive loop during the RF transmit period. The inductive loop can generate dense and sparse regions of the magnetic flux, which can be used to compensate for B₁ inhomogeneity. B-RAC was modeled in the numerical simulation, and the spatial distributions of B₁ and local SAR in a human model were analyzed. It was demonstrated that B-RAC can reduce B₁ inhomogeneity in a human model. B-RAC can reduce the maximum local SAR, and maintain B₁ inhomogeneity in the case of RF shimming alone. Therefore, using the B-RAC with RF shimming is more effective in reducing B₁ inhomogeneity and local SAR than using RF shimming alone.