阴道多通道柱状施源器旋转的剂量学影响研究

Study on the dosimetry effect of rotational errors of a multi-channel cylinder applicator of vagina

目的:探究子宫内膜癌术后阴道内照射中多通道柱状施源器旋转误差的剂量学影响。方法:选取2022年6-12月北京协和医院收治的18例行子宫内膜癌术患者,回顾性分析采用阴道多通道柱状施源器治疗的患者计划,保持与临床计划相同驻留模式,分别顺时针旋转22.5°和45.0°,模拟临床分次间施源器置入存在旋转误差的状态,分析两种旋转幅度下靶区和危及器官(OAR)的剂量学变化。结果:当施源器旋转22.5°时与临床计划相比,90%靶区体积接受的最小剂量(D_(90))降低了2.03%,差异有统计学意义(t=5.86,P<0.05),膀胱、直肠接受最大照射剂量的2cc体积内的最小剂量(D_(2cc))分别增加2.35%和2.71%,差异有统计学意义(t=-3.49、-2.40,P<0.05);当施源器旋转45°时与临床计划相比,靶区D_(90)降低了5.75%,差异有统计学意义(t=14.07,P<0.05),膀胱、直肠D_(2cc)分别增加6.50%和9.49%,差异有统计学意义(t=-7.72、-6.9,P<0.05);施源器旋转22.5°和45.0°后计划中乙状结肠和小肠的受量与原计划差异较小,且差异无统计学意义。结论:多通道柱状施源器在阴道内照射中可提供个体化的剂量分布,但在患者实施分次治疗时,需关注施源器的置入状态,避免与初始计划中施源器位置产生角度差异影响靶区及OAR剂量。

Objective:To investigate the dosimetry effect of rotational errors of multi-channel cylinder vaginal applicator of intravaginal irradiation after surgery of endometrial cancer.Methods:A total of 18 patients who underwent surgery of endometrial cancer at Peking Union Medical College Hospital from June to December 2022 were selected.The plans of patients who adopted the treatment of multi-channel cylinder applicator of vagina were retrospectively analyzed,which maintained the same retained mode with clinical plan.The applicator was rotated clockwise by 22.5°and 45.0°,respectively,simulating the rotational errors that occurred in placing the applicator among clinical inter-fractions.And then,the changes of dosimetry of target area and organs at risk(OAR)under two kinds of rotation amplitudes were further analyzed.Results:When the applicator was rotated as 22.5°,the minimum doses to 90%volumes of CTV by 2.03%than that of clinical plan,which was significantly different(t=5.86,P<0.05),and the maximal doses to 2cc of OARs of bladder and rectum respectively increased 2.35%and 2.71%,and the differences of them were statistically significant(t=-3.49,-2.40,P<0.05),respectively.When the applicator was rotated as 45°,the D_(90) of the target area decreased by 5.75%than that of clinical plan,which was statistically significant(t=14.07,P<0.05).The D_(2cc) values of the bladder and rectum increased respectively by 6.50%and 9.49%than that of clinical plan,which were statistically significant(t=-7.72,-6.9,P<0.05).The differences of the exposed doses of sigmoid colon and small intestine after the applicator was rotated by 22.5°and 45.0°between the plan and original plan were respectively less,which were not statistical significance.Conclusion:The multi-channel cylinder applicator can provide individualized dose distribution in intravaginal irradiation.However,attention should be paid to the placement of the applicator when patients undergo inter-fractional treatment,in order to avoid deviations in the angular alignment from the original plan.This can impact the dosages of the target area and OARs.