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 D_2cc of bladder, rectum, small bowel and sigmoid colon respectively; (ii) 19.3% and 18.9% in D_max of the left and right femoral heads (iii) 16.9% in D_95% 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.

简介。本研究旨在研究患者体位误差 (PSE) 对使用计划不确定性的容积调制弧治疗 (VMAT) 递送技术治疗的宫颈癌 IIB 期患者的靶标和风险器官 (OAR) 的剂量学和放射生物学影响Varian Eclipse 治疗计划系统的参数模块和内部开发的 DVH Analyzer 程序。材料和方法. 总共生成了 976 个 VMAT 计划来模拟基本计划中的 PSE，在 x–（横向）、y–（头尾）和 z–（前后位）中以 1 mm 的步长变化从 -10 mm 到 10 mm ) 方向。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，如一致性指数 (CI) 和同质性指数 (HI)，以及放射生物学量，如肿瘤控制概率 (TCP) 和正常组织控制概率 (NTCP)，都是从生成的 DVH 波段计算得出的使用内部开发的“DVH Analyzer”程序，与每个患者病例相关联的治疗计划队列。对提取的参数进行统计分析，并与没有 PSE 的基本计划的剂量学参数进行比较。结果. (i)膀胱、直肠、小肠和乙状结肠的D _2cc中的最大变化分别为2.4%、21.5%、0.8%、2.5% ；(ii)左右股骨头的D _max分别为19.3% 和 18.9% (iii) PTV 的 D 为 16.9 _% (iv) 乙状结肠的 NTCP 中的 12.1% 观察到 PSE 在各个方向上的变化。^{发现对于在 x +}、 y ⁺、 z ⁺方向上大于 4 mm和在 x ^-、 y ^-和 z ^-方向上分别大于 7 mm 的 PSE，TCP 会受到相当大的影响。结论. 本研究展示了 PSE 对采用 VMAT 技术治疗的宫颈癌病例的 TCP 和 NTCP 的影响，并建议每天进行图像引导以减轻 PSE 的影响。