Introduction. The present study aims to investigate the dosimetric and radiobiological impact of patient setup errors (PSE) on the target and organs at risk (OAR) of the cervix carcinoma stage IIB patients treated with volumetric-modulated arc therapy (VMAT) delivery technique using plan uncertainty parameters module of Varian Eclipse treatment planning system and in-house developed DVH Analyzer program.Materials and Methods. A total of 976 VMAT plans were generated to simulate the PSE in the base plan that varies from -10 mm to 10 mm in a step size of 1 mm in x- (lateral), y- (craniocaudal), and z- (anteroposterior) directions. The different OAR and tumor (PTV) volumes were delineated in each case. Various plan quality metrics, such as conformity index (CI) and homogeneity index (HI), as well as radiobiological quantities, such as tumor control probability (TCP) and normal tissue control probability (NTCP), were calculated from the DVH bands generated from the cohort of treatment plans associated with each patient case, using an in-house developed 'DVH Analyzer' program. The extracted parameters were statistically analyzed and compared with the base plan's dosimetric parameters having no PSE.Results. The maximum variation of (i) 2.4%, 21.5%, 0.8%, 2.5% in D2ccof bladder, rectum, small bowel and sigmoid colon respectively; (ii) 19.3% and 18.9% in Dmaxof the left and right femoral heads (iii) 16.9% in D95%of PTV (iv) 12.1% in NTCP of sigmoid colon were observed with change of PSE in all directions. TCP was found to be considerably affected for PSEs larger than 4 mm in x+, y+, z+directions and 7 mm in x-, y-and z-directions, respectively.Conclusion. This study presents the effect of PSE on TCP and NTCP for the cervix carcinoma cases treated with VMAT technique and also recommends daily image guidance to mitigate the effects of PSE.

中文翻译：

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使用Varian Eclipse治疗计划系统的计划不确定性参数模块，对接受容积调制弧光治疗的IIB期宫颈癌患者进行剂量分析。

介绍。本研究旨在利用计划不确定性研究采用容积调制弧光治疗（VMAT）递送技术治疗的IIB期宫颈癌患者的患者设置错误（PSE）对靶标和风险器官（OAR）的剂量和放射生物学影响Varian Eclipse治疗计划系统的参数模块和内部开发的DVH分析仪程序。材料与方法。总共生成了976个VMAT计划，以模拟基本计划中的PSE，x-（横向），y-（颅尾）和z-（前后）的步长为-10 mm至10 mm，步长为1 mm ）路线。在每种情况下都描绘了不同的OAR和肿瘤（PTV）体积。各种计划质量指标，例如合格指数（CI）和同质性指数（HI）以及放射生物学量，使用内部开发的“ DVH分析仪”程序，根据与每个患者病例相关的治疗计划队列生成的DVH谱带，计算出诸如肿瘤控制概率（TCP）和正常组织控制概率（NTCP）之类的信息。对提取的参数进行统计分析，并与基本计划中没有PSE的剂量参数进行比较。（i）膀胱，直肠，小肠和乙状结肠D2cc的最大变异分别为2.4％，21.5％，0.8％，2.5％；（ii）左右股骨头Dmax的Dmax分别为19.3％和18.9％（iii）PTV的D95％的Dmax为16.9％（iv）乙状结肠NTCP的12.1％随着PSE在各个方向的变化而变化。对于在x +，y +，z +方向上大于4 mm，在x-，y-和z方向上大于7 mm的PSE，TCP受到显着影响。