Using the STIR Optimization Method to Determine the Optimal Rung Drives for Resonators in High Field Head MRI
++ =+ = , during the optimization, both the magnitude 1 || B + and phase φ are weighted differently in the target function for different frequencies/coils. We note that in this investigation, all the rung currents, including the empty case, are determined via the STIR method, instead of using any predefined values [7]. Simulations Using the STIR optimization algorithm, the source profiles of the birdcage coils can be determined within two minutes on a 3-GHz PC. Fig.2 shows comparative results in terms of B1 field distribution before and after the optimization. The results clearly indicate that the optimization is quite capable of improving the uniformity of the RF field. About 85% of the B1-inhomogeneity caused by loading effects can be compensated for by optimizing the rung drives. Discussions In this preliminary study, we restrict ourselves to 2D scenarios [10], but the formalism can be easily adapted to other situations including 3D volume resonators and phased array systems. Optimal RF pulse modulation schemes are also being investigated for use with these structures. In addition, the algorithm is being applied to transceiver phased-array coils. It is hoped that theses studies will offer insight into coil design and/or useful imaging schemes for high field MRI.