In the study, a local approach to setting reference tolerance values for the distance-to-agreement (DTA) component of the gamma index is proposed. The reference tolerance values are calculated in simulations, following a dose delivery model presented in a previous work. An analytical model for determining the quantiles of DTA distribution is also proposed and verified. It is shown that the distributions of DTA values normalized with either quantiles or standard deviation of DTA distributions are universal over analyzed plans and points within a single plan. This enables statistically sound inference about the quality of dose delivery. In particular, based on the normalized distributions the comparison of planned and delivered doses can be formulated within the framework of statistical inference as a problem of multiple statistical testing. For every evaluated point P of a plan, one may formulate and test a null hypothesis that there is no delivery error against an alternative hypothesis that there is a delivery error in P. It is also shown that the proposed approach is more sensitive than the current standard approach to shift errors in high dose gradient regions.

在这项研究中，提出了一种本地方法来设置伽马指数的距离一致 (DTA) 分量的参考容差值。参考公差值是在模拟中计算的，遵循先前工作中提出的剂量输送模型。还提出并验证了确定DTA分布分位数的分析模型。结果表明，用分位数或 DTA 分布的标准差归一化的 DTA 值分布在分析的计划和单个计划内的点上是通用的。这使得能够对剂量输送的质量进行统计上的合理推断。特别是，基于归一化分布，计划和交付剂量的比较可以在统计推断的框架内制定，作为多重统计测试的问题。对于一个计划的P，人们可以制定并检验一个零假设，即没有交付错误，而另一种假设是P中存在交付错误。还表明，所提出的方法比当前标准方法对高剂量梯度区域中的偏移误差更敏感。