CT定位增强扫描对中下段食管癌放疗剂量的影响

Effect of Positioning-enhanced CT on Dose Calculations in 3-dimensional Conformal Radiotherapy of Mid-lower Thoracic Esophageal Cancer

目的观察静脉造影剂对中下段食管癌三维适形放疗剂量的影响。方法 8例中下段食管癌患者分别进行平扫和增强定位CT扫描,分别进行相同的靶区勾画和三维计划设计,记录增强CT计划每个照射野的跳数,然后在平扫CT计划中以相同的跳数计算剂量,比较肉眼肿瘤靶区(GTV)、计划靶区(PTV)以及危及器官的剂量。结果与增强CT比较,平扫CT的GTV、PTV平均剂量分别增加了2.06%和1.99%,差异有统计学意义(P<0.05)。肺、心脏、脊髓的平均剂量以及脊髓的最大剂量比较差异无统计学意义(P>0.05)。结论增强扫描对中下段食管癌三维适形放疗的剂量有显著差异,说明CT增强扫描对中下段食管癌放疗剂量有一定的影响,在治疗中必须考虑其影响。

Objective To evaluate the effect of an intravenous contrast agent on dose calculations in 3- dimension conformal radiotherapy of mid-lower thoracic esophageal cancer. Methods 8 patients with mid- lower thoracic esophageal cancer were given two sets of CT in the same position before and after intravenous contrast agent injections. Target volumes and organs at risk were delineated on the enhanced CT and all plans were copied on the non-enhanced CT. The radiation doses calculated from the two sets of CT were compared with regard to planning volumes（ FFV and GTV）, and the organ at-risk. Results The plans of the non-en- hanced CT increased the mean doses of PTV and GTV with significant differences（ P 〈 0.05 ）. The mean do- ses of GTV and PTV were increased 2.06% and 1.99% ,respectively. There were no statistically sigrfificant difference for the mean dose of lungs, heart and spinal cord and maximum dosage of spinal cord between two sets of plan （ P 〉 0.05 ）. Conclusion The contrast agent has significant effect on the dosage of 3-dimension- al conformal radiotherapy of mid-lower thoracic esophageal cancer. It should be taken into account in radio- therapy.