A novel passive shimming method for 0.7T biplanar superconducting MRI

A novel passive shimming method is proposed for 0.7T biplanar superconducting MRI. Conventional methods usually have some errors because of engineering approximation and nonlinear magnetization characteristic of shimming pieces. A magnetic-coupling model is adopted to calculate the magnetizations in each shimming piece, which is more reasonable. Niching genetic algorithm is applied to solve this complex and large-scale optimization problem. The theoretical results show that the homogeneity is effectively improved from 2284 ppm to 254 ppm and this method has superiority in accuracy and convergence. Experimental result is presented and analyzed at last.