Das I J, Kahn F M
Department of Therapeutic Radiology, University of Minnesota Hospital, Minneapolis 55455.
Med Phys. 1989 May-Jun;16(3):367-75. doi: 10.1118/1.596345.
Most computer algorithms used clinically for photon beam treatment planning are unable to predict the effect of electron backscattering on dose distribution from high atomic number materials. It has been observed that there is a significant dose enhancement at such an interface. We define the dose enhancement in terms of backscatter dose factor (BSDF), which depends on the energy of the photon beam, thickness and width of the inhomogeneity, distance from the interface, and the atomic number of the inhomogeneity. For all energies studied, the dose fall-off is initially very rapid and disappears beyond a few millimeters upstream from the interface. Empirically derived equations are presented for dose calculation at the interfaces of various media, including bone and soft tissue, for photon energies in the range of Co-60 gamma rays to 24 MV x rays.
临床上用于光子束治疗计划的大多数计算机算法无法预测电子反向散射对高原子序数材料剂量分布的影响。据观察，在这样的界面处会有显著的剂量增强。我们根据反向散射剂量因子（BSDF）来定义剂量增强，该因子取决于光子束的能量、不均匀性的厚度和宽度、距界面的距离以及不均匀性的原子序数。对于所有研究的能量，剂量下降最初非常迅速，并且在距界面上游几毫米之外消失。给出了经验推导的方程，用于计算在包括骨和软组织在内的各种介质界面处的剂量，适用于钴 - 60γ射线至24兆伏X射线范围内的光子能量。
