Department of Radiation Oncology and Medical Physics, Graduate School of Medicine, Sapporo Medical University, S1 W6 Chuo-ku, Sapporo, Japan.
J Radiat Res. 2012 Jul;53(4):615-9. doi: 10.1093/jrr/rrs003. Epub 2012 Jun 6.
We investigated the uncertainty in patient set-up margin analysis with a small dataset consisting of a limited number of clinical cases over a short time period, and propose a method for determining the optimum set-up margin. Patient set-up errors from 555 registration images of 15 patients with prostate cancer were tested for normality using a quantile-quantile (Q-Q) plot and a Kolmogorov-Smirnov test with the hypothesis that the data were not normally distributed. The ranges of set-up errors include the set-up errors within the 95% interval of the entire patient data histogram, and their equivalent normal distributions were compared. The patient set-up error was not normally distributed. When the patient set-up error distribution was assumed to have a normal distribution, an underestimate of the actual set-up error occurred in some patients but an overestimate occurred in others. When using a limited dataset for patient set-up errors, which consists of only a small number of the cases over a short period of time in a clinical practice, the 2.5% and 97.5% intervals of the actual patient data histogram from the percentile method should be used for estimating the set-up margin. Since set-up error data is usually not normally distributed, these intervals should provide a more accurate estimate of set-up margin. In this way, the uncertainty in patient set-up margin analysis in radiation therapy can be reduced.
我们使用包含少数临床病例且时间跨度较短的小型数据集来研究患者摆位误差分析中的不确定性，并提出了一种确定最佳摆位误差的方法。对 15 例前列腺癌患者的 555 次配准图像的患者摆位误差进行了正态性检验，采用了分位数-分位数 (Q-Q) 图和柯尔莫哥洛夫-斯米尔诺夫检验，假设数据不是正态分布的。摆位误差范围包括整个患者数据直方图 95%区间内的摆位误差，并且对它们的等效正态分布进行了比较。患者摆位误差呈非正态分布。当假设患者摆位误差分布呈正态分布时，在一些患者中会低估实际摆位误差，但在另一些患者中会高估。当使用仅包含短时间内少数病例的小型数据集来分析患者摆位误差时，应该使用百分位数法从实际患者数据直方图的 2.5%和 97.5%区间来估计摆位误差。由于摆位误差数据通常不是正态分布的，因此这些区间可以更准确地估计摆位误差。通过这种方式，可以降低放射治疗中患者摆位误差分析的不确定性。
