俄歇电子发射核素靶向治疗中细胞平均吸收剂量的计算

目的 给出一种新的方法，计算俄歇电子发射核素在细胞中均匀分布和非均匀分布时细胞和细胞核的平均吸收剂量以吸引剂量在细胞内的分布。方法 俄歇电子单位路径的能量损失用多项式拟合，用解析方法给出点源在细胞或细胞核内的能量沉积，从而得到不同源－靶组合的S值。放射性核素在细胞中径向线性分布和指数分布，分别计算了细胞和细胞核的平均吸收剂量；以及放射源距细胞中心不同距离时对细胞吸收剂量的影响。光子对细胞或细胞核的剂量贡献忽略不计。结果 平均吸收剂量及其在细胞内的分布和细胞的大小、俄歇电子能谱、核素的空间分布密切相关。细胞核内的核素对细胞核吸收剂量的贡献远大于细胞质中的核素。结论 俄歇电子在生物组织中的射程短，单位路径的能量损失高，能产生非常高的局部能量沉积。我们给出的细胞平均吸收剂量的解析计算方法计算速度快，结果可靠。

Mean absorbed dose calculation at cellular level for targeted radiotherapy using Auger-electron-emitters

Objective\ To calculate the mean absorbed doses at celluar and subcellular levels for uniformly and non\|uniformly distributed Auger electron emitters. Methods\ The energy deposited in cell or nucleus by Auger electrons was analytically calculated using the polynomial representation of energy loss.S\|values were subsequently computed for several target\|source combinations.The absorbed dose and dose distribution were calculated for spherically symmetric radionuclide distributions depending linearly and exponentially on the radial position.The dose profile as a function of the source radial coordinate was also evaluated for typical cell sizes.The contributions of photon radiation to absorbed dose in cells were ignored. Results\ The mean absorbed dose and dose distribution depend largely on the size of target cells,the radiation spectrum and intracellular localization and distribution of radionuclides.The contribution of intranuclear radionuclides to mean absorbed dose was larger than that of extranuclear ones. Conclusion\ Auger electrons can produce high local energy deposition in cells because of their very low energies and extremely short ranges.Our dose calculation method is simple.The results are reliable and can be used in many fields.