Purpose

Patients receiving postoperative irradiation for uterine cervical cancer might not be able to eat during radiation therapy because of the effects of concurrent chemo-radiotherapy; this may lead to changes in the patient’s body shape during treatment. When performing image-guided radiotherapy, it is necessary to determine immediately whether treatment can be performed on the day or whether re-planning is required. The purpose of this study was to determine indicators for re-planning by examining the effects of changing body contours on radiation therapy dose.

Materials and methods

The original body contour was reduced by 1 cm in the front portion (structure-set 1). Based on the original dose distribution, the dose recalculation was performed with a structure set created using the body contour of structure-set 1. The difference between the original and recalculated dose distributions of structure-set 1 was evaluated through gamma analysis (GA).

Result

In the GA results for dose distribution obtained via recalculation with structure-set 1, a pass rate of 90% or more was obtained for a criterion of 2 mm/2% in all cases.

Conclusions

The results suggest that dose re-planning is rarely required when the body shape is reduced by only 1 cm in the front.

中文翻译：

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宫颈癌手术后身体轮廓的变化对放射治疗剂量分布的影响。

目的

由于同时放化疗的影响，接受子宫颈癌术后放射治疗的患者可能无法在放射治疗期间进食。这可能会导致患者在治疗过程中身体形态发生变化。在进行图像引导放射治疗时，有必要立即确定是否可以在当天进行治疗或是否需要重新计划。这项研究的目的是通过检查改变身体轮廓对放射治疗剂量的影响来确定重新计划的指标。

材料和方法

车身前部的原始轮廓减小了1 cm（结构组1）。基于原始剂量分布，使用结构集1的身体轮廓创建的结构集执行剂量重新计算。结构集1的原始剂量分布和重新计算的剂量分布之间的差异通过伽马分析（GA）进行评估。

结果

在通过结构集1的重新计算获得的剂量分布的GA结果中，在所有情况下，对于2 mm / 2％的标准，获得90％或更高的通过率。

结论

结果表明，当身体形状仅在前面减小1厘米时，很少需要重新规划剂量。