中文说明：此算法是Siddon提出的逐行求焦点算法，可以很快地计算出系统矩阵，对于初学者而言，有很好的学习作用，可以作为学习Matlab和图像重建的参考。
English Description：
This algorithm is proposed by Siddon to get the systematica metrics by find the focus line by line. It is a good reference for beginner if he want to know about the image rebuiding