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目的探讨胸中段食管癌在三维适形放疗(3DCRT)中靶区移位的变化及放疗过程中复位对靶区剂量学、正常组织剂量学的影响,讨论3DCRT中复位的必要性及可行性。方法选择15例胸中段食管癌患者接受40Gy治疗后进行复位,利用图像融合观察肿瘤靶区移动范围。制定定位和复位两套放疗计划,对比复位后对靶区D100、D95及肺平均、心脏平均、脊髓最大剂量的影响。结果胸中段食管癌患者在放疗40Gy后,肿瘤计划靶体积(PTV)边缘头脚方向平均移位0.5cm(0.41～0.45),前后方向平均移位0.2cm(-0.3～0.6cm),左右方向平均移位0.2cm(-0.7～0.5cm),差异均无统计学意义(P<0.05),头脚方向回缩最明显。肿瘤靶区D100及D95两个指标比较具有统计学意义。肺平均、心脏平均、脊髓最大剂量指标变化无统计学意义,但其数值上比较,复位计划(plan 2)中正常组织受照剂量均比定位计划(plan 1)小。结论胸中段食管癌患者在三维适形放疗中进行复位可减少靶区移位影响,同时更改放疗计划可减少正常组织的受照剂量,有必要进行复位。
Objective To investigate the changes of target area displacement in esophageal cancer of the middle and lower esophagus in three-dimensional conformal radiotherapy (3DCRT) and the influence of reduction on dosimetry and normal tissue dosimetry during the course of radiotherapy. To discuss the necessity and feasibility of reduction in 3DCRT. Methods Fifteen patients with esophageal cancer of the thoracic segment underwent 40 Gy treatment and then were resected. Image fusion was used to observe the movement range of the target tumor. To establish two sets of radiotherapy and positioning plans and reset plans to compare the target area D100 and D95 after reset and lung average, average heart and spinal cord maximum dose. Results After esophageal cancer was treated with 40Gy of radiotherapy, the mean PTV displacement of the head and toe of the tumor was 0.5cm (0.41-0.45) and the average displacement was 0.2cm (-0.3-0.6cm) in the anterior and posterior directions. The mean displacement was 0.2cm (-0.7 ~ 0.5cm), with no significant difference (P <0.05). The retraction of head and toe direction was the most obvious. Tumor target area D100 and D95 two indicators were statistically significant. Mean lung, mean heart, and maximum spinal cord dose did not change statistically, but numerically, the normal tissue exposure dose in plan 2 was less than that in plan 1. Conclusions The reduction of target area shift in patients with esophageal carcinoma of the thorax in the course of three-dimensional conformal radiotherapy can reduce the dose of the normal tissue. It is necessary to reset the esophageal cancer patients.