Huang P H, Kase K R, Bjärngard B E
Med Phys. 1982 Sep-Oct;9(5):695-702. doi: 10.1118/1.595131.
The use of transmission measurements with combinations of attenuating materials has been investigated as a method of determining the x-ray energy spectrum from a 4-MV linear accelerator. Simulation studies have been made with three 4-MV x-ray spectra of slightly different shapes. From each of these spectra, the narrow beam transmission curve was calculated, using lead to attenuate the beam for the first several points. Aluminum was then added to attenuate the beam to 0.001 of its initial intensity. A computer program using an iterative least-squares technique has been developed to analyze the transmission data and determine the spectrum by applying some physically reasonable sensible constraints. The calculated transmission values agreed with the simulated data within the estimated experimental uncertainties, and it is concluded that the technique is reliable for the spectral reconstruction and is sensitive to small spectral changes.
利用衰减材料组合进行透射测量，已被作为一种从4兆伏直线加速器确定X射线能谱的方法进行了研究。已针对三种形状略有不同的4兆伏X射线能谱开展了模拟研究。从这些能谱中的每一个出发，计算窄束透射曲线，在前几个点使用铅来衰减束流。然后添加铝将束流衰减至其初始强度的0.001。已开发出一个使用迭代最小二乘法技术的计算机程序，以分析透射数据，并通过应用一些物理上合理的明智约束来确定能谱。计算得到的透射值在估计的实验不确定度范围内与模拟数据相符，得出的结论是，该技术对于能谱重建是可靠的，并且对小的能谱变化敏感。
