双能计算机层析成像(CT)投影分解是双能CT预处理重建算法的关键步骤,在采用迭代算法求解双能投影积分方程组时,迭代初值的选择对迭代的收敛性影响很大。为了解决双能投影积分方程组迭代求解的初值选择问题,提出一种优化迭代算法。该算法在计算双能基材料投影查找表以及进行系统标定时,依据高低能投影数据的数值范围,设置一定的步长,按照高低能投影值的大小依次求解对应的基材料投影,并以上次的收敛结果作为下次迭代的初值。结果表明,该优化迭代算法有效改善了迭代的收敛性,提高了双能CT系统标定的效率,验证了算法的有效性。

Projection decomposition of dual-energy computed tomography (CT) is a key step for dual-energy CT pre-reconstruction algorithm. The selection of iterative initial values has great influence on the convergence of the iteration when an iterative algorithm is use to solve the dual-energy projection integral equations. To solve the problem of selecting initial values in solving dual-energy projection integral equations, an optimized iterative algorithm is proposed. For calculating projection lookup tables of dual-energy basis materials and calibrating the system, a certain step length is set based on numerical ranges of high-energy and low-energy projection data. Thus the corresponding basis materials projection can be solved according to the order of the projection values. The convergent result of last time is taken as the initial value of next iteration. The results show that the proposed algorithm can effectively improve the convergence of the iteration and the efficiency of calibration of the duel-energy CT system, which proves the validity of the algorithm.