中文说明：CT图像的重建过程就是图像处理机解方程的过程，理论上的方法很多，但实际使用最多的只有几种。直接反投影法也称累加法，是最简单，最老式的方法。直接反投影所产生的图像边缘的云晕状伪影在数学上称为对原图像的一次褶积，要去除伪影就需要再做褶积解除，这一数学修正，它也叫滤波，就是在每一个投影波形上加上一个修正用的函数波形。
English Description：
CT image reconstruction process is the process of solving equations of image processing machine, in theory, many methods, but only a few of the most used. Method of direct back projection method, also known as cumulative, is the simplest, most old-fashioned way. Direct back-projection of the edge of the cloud Halo artifact is mathematically known as the convolution of the original image to remove artifacts need further convolution lifted, a mathematical correction, which is also called filtering, is in every add a revision to projected wave function waveform.