X射线成像系统可以通过其点扩展函数来表征,其点扩展函数分为一次射线点扩展函数和散射点扩展函数两部分。在分析点扩展函数各个影响因素的基础上,建立了以物体厚度、物体到探测器距离以及成像几何设置为参量的解析模型。利用该模型推导出了特定入射射线能谱和射线源到探测器距离情况下散射比的计算公式。它是以物体厚度和物体到探测器距离为变量的函数。在利用实验数据对模型参量进行最优估计的基础上,利用散射比实验验证了模型的正确性。为散射和几何不清晰度的消除提供了一种实用的模型依据。

The functioning of an X-ray imaging system is well characterized by its point spread function (PSF). The point spread function consists of prime point spread function and scatter point spread function. A point spread function model is developed for X-ray imaging system. Parameters in the model include part thickness, source to detector distance and geometric parameters. Based on the model, an analytical expression for the scatter fraction is derived and it is a function of part thickness and source to detector distance. Experiment result proves correctness of the model by comparing calculated scatter fraction and the one measured from experiment. The model gives an estimation of scatter and geometric blur for their removal and is an effective model for X-ray imaging.