外扩胃和十二指肠轮廓提高放射治疗自动勾画安全性的效果

目的 探讨自动勾画的危及器官(Organs at risks, OAR)的外扩对各类型剂量评估参数的影响。方法 收集50例在2019年至2021年内接受过上腹部放疗的患者CT图像,自动和人工勾画胃和十二指肠的轮廓。Mann-Whitney U检验用于评估胃和十二指肠自动勾画结果在戴斯相似系数(Dice Similarity Coefficient, DSC)和95%豪斯多夫距离(95% Hausdorff Distance, HD95)方面的差异。结合临床使用的剂量分布,计算胃和十二指肠自动勾画引起的剂量差异。采用Wilcoxon秩和检验评估不同的外扩距离引起的剂量评估参数差异的变化。采用bootstrap法计算各差异均值95%置信区间的下限。寻找所需的最小外扩距离,使得外扩后的结构所对应的剂量评估参数大于或等于手动勾画OAR的剂量评估参数。结果 胃的DSC和HD95均优于十二指肠,Mann-Whitney U检验提示差异显著。外扩操作对最高剂量差异影响显著,采用Wilcoxon秩和检验比较任何相邻组之间的结果,p值均为0。外扩操作对平均剂量差异或V₃₀差异没有影响。在DSC大于0.8的情况下,外扩大约7mm时,可以保证外扩结构的最高剂量大于或等于手动勾画的OAR；外扩5mm时,可以保证即使外扩结构的最高剂量低于人工勾画的OAR,其差异也不会超过1Gy。结论 随着自动勾画OAR的外扩,最高剂量会发生变化,而平均剂量和DVH参数不会发生变化。研究证实,外扩一定距离,可以保证外扩后的结构所对应的最高剂量大于等于人工勾画OAR对应的最高剂量。

Effect of expanding stomach and duodenum to improve the safety of auto-contouring in radiotherapy

Objective To investigate how various dose evaluation parameters have changed because of the expansion of auto-contouring Organs at Risk (OAR). Methods The stomach and duodenum were automatically and manually contoured on the CT scans of 50 individuals who had upper abdominal radiotherapy within the previous three years. Mann-Whitney U test was used to assess the difference between stomach and duodenum auto contouring results in terms of Dice similarity coefficient (DSC) and 95% Hausdorff distance (HD95). To calculate the dose difference induced by auto contouring with the clinically applied dose distribution. The Wilcoxon rank sum test was utilized to evaluate the variation of the dose evaluation parameters caused by the different expansion distance. The calculation of the lower limits of the 95% confidence interval for each difference averages. To find the minimum expansion distance required when the dose evaluation parameter corresponding to the expanded structure was greater than or equal to that for the manual contoured OAR. Results The DSC and HD95 of stomach were superior to those of the duodenum and the Mann-Whitney U test revealed that there was a significant difference. The expansion procedure had a substantial impact on the difference in the maximum dose. The Wilcoxon rank sum test was employed to compare the results between any adjacent groups, and the p value was 0. The expansion procedure had no effect on the mean dose difference or V₃₀ difference. The maximum dose of the expanded structure can be guaranteed to be larger than or equal to the manually contoured OAR when the outer expansion is around 7mm, and it can be guaranteed that difference will not be greater than 1Gy, even if it is less than the OAR that was manually contoured when the outer expansion is 5mm and when the DSC is greater than 0.8. Conclusions The maximum dose will change as the auto contoured OAR expanded, and the mean dose and DVH parameters will not. Studies have confirmed that a certain distance of expansion can ensure that the maximum dose corresponding to the expanded structure is greater than or equal to the maximum dose corresponding to the manually contoured OAR.