Droege R T, Bjärngard B E
Med Phys. 1979 Nov-Dec;6(6):515-8. doi: 10.1118/1.594615.
The MTF of metal screen film detectors used in radiation treatment verification has been measured at 4 and 8 MV x-ray energies. The results show that lead screens provide better resolution than copper screens, and a single-emulsion film offers considerable advantage over the traditional double-emulsion film. A rear lead screen was found to seriously degrade the resolution properties of a front lead screen single-emulsion film detector. The detector MTF was found to be energy dependent. In general, both the low and the high spatial frequency response decreased with increasing x-ray energy. This, in part, accounts for the noticeable image quality difference between 4 and 8 MV radiographs.
已在4兆伏和8兆伏的X射线能量下测量了用于放射治疗验证的金属屏片探测器的调制传递函数（MTF）。结果表明，铅屏比铜屏提供更好的分辨率，并且单乳剂胶片比传统的双乳剂胶片具有相当大的优势。发现后铅屏会严重降低前铅屏单乳剂胶片探测器的分辨率特性。探测器的MTF被发现与能量有关。一般来说，低空间频率响应和高空间频率响应都随着X射线能量的增加而降低。这在一定程度上解释了4兆伏和8兆伏射线照片之间明显的图像质量差异。
