食管癌常规及两种适形照射方法剂量分布的比较

Comparison of the dose distribution in conventional and conformal radiotherapy by 3DRTP for esophageal carcinoma

目的采用三维治疗计划系统比较食管癌常规三野照射和两种三维适形放疗（3DCRT）计划中肿瘤和正常组织的剂量分布。方法随机选择食管癌患者10例，CT扫描定位。勾画肿瘤体积（GTV）、临床靶体积（CTV）和计划靶体积（PTV）。设计常规三野、三野适形、五野适形3种设野。结果（1）三野适形与常规三野比较：三野适形中GTV均在90％剂量线以内，而在常规三野计划中有50％（5／10）部分GTV在90％等剂量线以外；PTV的最小剂量、平均剂量差异均有统计学意义；脊髓剂量分布差异有统计学意义。（2）五野适形与三野适形比较：PTV最小剂量差异有统计学意义。五野适形中20、30Gv包绕的百分体积变小，10Gy包绕的百分体积增大，差异有统计学意义；脊髓最大剂量差异有统计学意义，但在安全范围内。结论（1）三野适形计划的肿瘤和脊髓剂量分布优于常规三野放疗计划，尤其在病变较长时更有优势；（2）五野适形较三野适形肿瘤剂量分布更趋均匀，双肺和脊髓剂量都在安全范围内。

Objective To assess the dose distribution in different plans of conventional radiotherapy （2DRT）and two 3-dimensional conformal radiation therapy （3DCRT） by three dimensional conformal radiation treatment.planning （3DRTP） for the primary lesion and normal surrounding tissues around esophageal carcinoma. Method 10 patients with esophageal carcinoma were enrolled randomly, they were marked simulated by CT. GTV, CTV and PTV were outlined, three treatment plans were designed： conventional technique, 3DCRT, 5DCRT. Results ①Comparing to 2DRT, the dose distribution of GTV in 3DCRT was in 90 % dose line, but 50 % was without that in 2DRT, the difference in Dmin,Dmean of PTV was obvious,the dose distribution of spinal cord was different obviously （P 〈0.05）. ② Dmin of PTV was obvious between 5DCRT and 3DCRT. The volumes was significantly discreased in 20 Gy, 30 Gy and increased in 10Gy in 5DCRT, Dmax of spinal cord was significantly discreased （P 〈0.05） and in the safety range. Conclusions ③ The dose distribution of tumor and spinal cord in 3DCRT is better than in 2DRT, especially when the length of the field increased.②SDCRT can achieve ideal tumor dose distribution compared with 3DCRT, the dose of bilateral lungs and spinal cord is in the safety range.