Niemierko A
Department of Radiation Oncology, Massachusetts General Hospital, Boston 02214, USA.
Med Phys. 1997 Jan;24(1):103-10. doi: 10.1118/1.598063.
Modern treatment planning systems for three-dimensional treatment planning provide three-dimensionally accurate dose distributions for each individual patient. These data open up new possibilities for more precise reporting and analysis of doses actually delivered to irradiated organs and volumes of interest. A new method of summarizing and reporting inhomogeneous dose distributions is reported here. The concept of equivalent uniform dose (EUD) assumes that any two dose distributions are equivalent if they cause the same radiobiological effect. In this paper the EUD concept for tumors is presented, for which the probability of local control is assumed to be determined by the expected number of surviving clonogens, according to Poisson statistics. The EUD can be calculated directly from the dose calculation points or, from the corresponding dose-volume distributions (histograms). The fraction of clonogens surviving a dose of 2 Gy (SF2) is chosen to be the primary operational parameter characterizing radiosensitivity of clonogens. The application of the EUD concept is demonstrated on a clinical dataset. The causes of flattening of the observed dose-response curves become apparent since the EUD concept reveals the finer structure of the analyzed group of patients in respect to the irradiated volumes and doses actually received. Extensions of the basic EUD concept to include nonuniform density of clonogens, dose per fraction effects, repopulation of clonogens, and inhomogeneity of patient population are discussed and compared with the basic formula.
现代三维治疗计划系统可为每位患者提供三维精确剂量分布。这些数据为更精确地报告和分析实际输送到受照射器官及感兴趣体积的剂量开辟了新的可能性。本文报道了一种总结和报告非均匀剂量分布的新方法。等效均匀剂量（EUD）概念假定，如果任何两种剂量分布产生相同的放射生物学效应，则它们是等效的。本文介绍了肿瘤的EUD概念，根据泊松统计，假定局部控制概率由存活克隆原细胞的预期数量决定。EUD可直接从剂量计算点或相应的剂量体积分布（直方图）计算得出。选择2 Gy剂量下存活的克隆原细胞分数（SF2）作为表征克隆原细胞放射敏感性的主要操作参数。在临床数据集上展示了EUD概念的应用。由于EUD概念揭示了所分析患者组在受照射体积和实际接受剂量方面的更精细结构，观察到的剂量反应曲线变平的原因变得明显。讨论了基本EUD概念的扩展，包括克隆原细胞密度不均匀、分次剂量效应、克隆原细胞再增殖以及患者群体的不均匀性，并与基本公式进行了比较。
