B1inhomogeneity effect reduction for 2D spatial selective RF pulse using simulated annealing

With the development of the highfield MRI system, the RF field inhomogeneity becomes a challenging problem in high flip angle excitation. In this study, a new RF pulse design method is proposed, which combines the simulated annealing SA algorithm and the kspace method to attain a pulse which can compensate the RF field inhomogeneity effect. The RF pulse envelope is firstly initiated using the kspace method and a cost function which contains the passband error and stopband error is defined. Then the SA is applied to refine the RF pulse shape to achieve lowcost value. Finally, under inhomogeneous RF field an optimized RF pulse with improved flip angle accuracy can be obtained. Simulation results show that when compared with the pulse designed only using the kspace method, the passband error can be decreased by 28, 40, and 75 for 90° excitation pulse, refocusing pulse, and 180° inversion pulse, respectively. © 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part B Magn Reson Engineering 33B: 75–83, 2008