Falco T, Fallone B G
Medical Physics Unit, McGill University, Montreal General Hospital, Canada.
Med Phys. 1998 Dec;25(12):2455-62. doi: 10.1118/1.598436.
Measurements of modulation transfer function (MTF) for front and back metal-plate/film portal detectors are reported for the Cobalt-60 and 10 MV spectra. The detectors consist of a double-emulsion portal film secured between plates of Al, Cu, brass, or Pb with thicknesses varying from 0 to 4.81 mm. Secondary electrons produced within the front plate generate the main signal, but the MTF decreases with an increase in front plate thickness greater than the maximum range of electrons Rmax because of photon scatter in the front plate. Because the decrease of MTF with backplate thickness ceases for backplate thickness greater than Rmax, the MTF is influenced more by the backscatter electrons than the backscatter photons.
报告了针对钴 - 60 和 10 兆伏能谱，对前后金属板/胶片型射野探测器调制传递函数（MTF）的测量结果。探测器由夹在铝、铜、黄铜或铅板之间的双乳剂射野胶片组成，板的厚度在 0 至 4.81 毫米之间变化。前板内产生的二次电子产生主要信号，但由于前板中的光子散射，当 front plate thickness（此处原文可能有误，推测为前板厚度）大于电子的最大射程 Rmax 时，MTF 会随着前板厚度的增加而降低。由于当背板厚度大于 Rmax 时，MTF 随背板厚度的减小停止，因此 MTF 受反向散射电子的影响比反向散射光子更大。
