Beernink K P, Nelson R F, Chilton A B
Radiat Res. 1983 Nov;96(2):429-34.
Two different sets of Monte Carlo computations were carried out for the study of dose penetration of monoenergetic, low-energy (10 to 100 keV) photon beams incident on slabs of tissue. One program took into account coherent scattering and considered electron binding when finding the angle of scattering during incoherent scattering; the other simpler program, customarily used at higher energies, largely ignored these effects. For calculations at the source photon energy of 100 keV, it was found that there was negligible difference in dose distribution in the slab between the more and less complex type of calculations. The same thing was found to be true for the 30 and 10-keV source photon energies only for shallow penetration distances; and at deeper penetrations the simple approach tended to overestimate the dose appreciably. It is concluded that for penetration of low-energy photon beams into tissue, accurate calculational results cannot be assured with the neglect of coherent scattering effects and electron binding considerations in determining the scattering angles except for shallow depths of penetration.
为了研究单能低能（10至100 keV）光子束入射到组织平板上的剂量穿透情况，进行了两组不同的蒙特卡罗计算。一个程序考虑了相干散射，并在非相干散射过程中寻找散射角时考虑了电子束缚；另一个更简单的程序，通常在较高能量下使用，很大程度上忽略了这些效应。对于源光子能量为100 keV的计算，发现平板中剂量分布在更复杂和较不复杂的计算类型之间差异可忽略不计。对于30 keV和10 keV的源光子能量，仅在浅穿透深度时情况相同；而在较深穿透时，简单方法往往会明显高估剂量。得出的结论是，对于低能光子束穿透组织的情况，除了浅穿透深度外，在确定散射角时忽略相干散射效应和电子束缚考虑因素，无法确保获得准确的计算结果。
