闪光照相系统的散射分布与降散射的数值模拟

 对法国试验客体（FTO）的3 m照相系统建模，利用Monte-Carlo方法模拟X光子输运过程，得到了系统的散射分布和系统器件对散射的贡献。结果表明：后保护锥是系统散射的主要来源，对于任意一点，后保护锥的散射占总散射的75%以上。FTO的散射主要是FTO外层材料和边缘的散射，这部分散射占客体总散射的90%以上。利用坡度准直器对系统散射严重的区域进行的降散射，表明坡度准直器是一个很好的降散射器件，能有效提高图像质量。

Numerical simulation of distribution of scattered exposure and reduced scatter in flash radiographic system

A Monte-Carlo method is used to simulate the transport process of X-ray photons in a model which is made by a 3 m radiographic system for FTO. The scatter distribution of system and the contribution of each cell to the scatter are obtained. It is shown that the back-protected-cone(BPC) is the main source of the scatter in the system.For any pixel, the scattered exposure from the BPC is more than 75% of the total exposure. The outer materials and the edge of FTO produce the main scatter of the object. In order to reduce the scatter of the edge of FTO and BPC, a graded collimator is used in the radiographic system. The graded collimator can reduce the scatter exposure effectively and effectively improve the image quality.