OSEM has good reconstructed image quality and uses less computation time.Overrelaxation technique has adjustable relaxed parameters and speeded convergence function.

• 有序子集最大期望法(OSEM)具有较高的重建图像质量和较短的计算时间，超松弛因子(OR)有可灵活调节超松弛因子和加速收敛两种功效。