CR、DR倾斜中心线摄影斜射效应的对比研究

An experimental comparison of parallactic unsharpness for DR and CR with oblique central ray projection

目的 探讨计算机X线摄影（computerized radiography,CR）和数字X线摄影（digital radiography,DR）在倾斜中心线摄影时的斜射效应状况。方法 对于CR和DR两种摄影方式,分别把中心线倾斜0、15、30、45对矩形波测试卡曝光,然后测定预采样调制传递函数（modulation transfer function,MTF）并绘制MTF曲线。结果 1）对于CR,不同中心线倾角的MTF曲线随中心线倾角的增大而略微降低,极限分辨率无变化;2）对于DR,不同中心线倾角的MTF曲线随中心线倾角的增加而略有明显降低,极限分辨率保持不变。结论 在中心线倾斜0-45°的角度范围内,CR和DR仅存在比较小的X线斜射效应,而且前者还略好于后者。

Objective To study on the parallactic unsharpness of computerized radiography （CR） and digital radiography （DR） with oblique central ray projection. Methods For CR and DR system, square wave test chart was exposed with oblique central ray projection angled of 0, 15, 30, and 45, respectively, and then, we measured pre-sampling modulation transfer function （MTF） and draw the MTF curves. Results 1 ） For CH, the MTF curve of different central ray angle drops slightly with the eentral ray angle increases, but the limiting resolution is not changed ; 2 ） For DR, the MTF curve of different central ray angle drops slightly obviously with the center ray angle increases, but the limiting resolution is also not changed. Conclusion There is only slight parallactic unsharpness for CR and DR with the central ray angled 0 -45° , and the former is slightly better than the latter.