左乳癌根治术后胸壁电子线和3D-CRT照射的剂量学研究

Dosimetric Study on the Electron Beam Irradiation and the 3D-CRT on the Chest Wall After Left-sided Radical Mastectomy

目的探讨左乳腺癌改良根治术后胸壁电子线照射和三维适形照射的剂量学特点。方法选取左乳腺癌改良根治术后10例患者,采用pinnacle3 9.6计划系统分别设计胸壁电子线照射和三维适形照射计划,比较两种放疗计划的剂量学参数。结果三维适形放疗靶区剂量Dmax、Dmin、Dmean、V90、V95、V100和D95比电子线放疗明显增大,两组比较差异有统计学意义(P<0.05);V105、V110和D5差异不明显,两组比较差异无统计学意义(P>0.05);CI电子线放疗优于三维适形放疗,HI三维适形放疗明显优于电子线放疗,两组比较差异有统计学意义(P<0.05);危及器官左肺V5、V10、V15、V20、V30、V40和Dmean,心脏V5、V10和V15三维适形放疗比电子线放疗明显降低,两组比较差异均有统计学意义(P<0.05),心脏V20和Dmean三维适形放疗比电子线放疗略下降,而V30和V40则略有升高,但两组比较差异无统计学意义(P>0.05);右肺Dmean三维适形放疗比电子线放疗略有升高,两组比较差异无统计学意义(P>0.05)。结论三维适形放疗的靶区剂量分布以及对患侧肺和心脏的保护明显优于电子线放疗,在胸壁表面放置0.5 cm厚的等效填充物既能使靶区剂量分布更加均匀又降低了心肺的受照剂量。

Objective To compare the dosimetric characteristics of three dimensional conformal radiation therapy（3 DCRT） and electron beam irradiation on the cheat wall for patients receiving left-sided modified radical mastectomy. Methods 10 patients who received left-sided modified radical mastectomy were enrolled. The pinnacle 39. 6 planning system was adopted to design two treatment plans on the chest wall,respectively,which were the electron beam irradiation and the 3 DCRT plan; and the dosimetric parameters of the two radiotherapy plans were compared. Results In terms of the target volume dose,the maximum dose（ Dmax）,minimal dose（Dmin）,mean dose（Dmean）,V90,V95 and V100 irradiation were obviously higher than those of electron beam radiotherapy,with statistically significant differences（ P〈 0. 05）; there were no significant differences in V105 and V110 and D5,with no significant differnces（ P〉 0. 05）. The conformity index（ CI） of electron beam was better than that of 3 DCRT,while the homogeneity index（ HI） of3 DCRT was superior to that of electron beam,and the differences between electron beam and 3 DCRT were statistically significant（ P〈 0. 05）. Regarding the organs at risk,the V5,V10,V15,V20,V30,V40 and Dmeanof left lung,as well as V5,V10 and V15 of heart,were remarkably lower in 3 DCRT than those in electron beam radiotherapy,and the differences were statistically significant（ P〈 0. 05）; the V20 and Dmeanof heart in 3 DCRT group were slightly lower than those in electron beam radiotherapy,whereas the V30 and V40 of heart in 3 DCRT were slightly higher than those in electron beam radiotherapy,and there was no statistical significance（ P〉 0. 05） between the two groups. The Dmeanof right lung in 3 DCRT was slightly higher than that in electron beam radiotherapy,but there was no statistical significance between the two groups（ P〉 0. 05）. Conclusion 3 DCRT has more significant advantages over the electron beam radiotherapy on the distribution of target volume and the protection of heart and left lung. By using the 0. 5 cm-in-thickness equivalent filler upon the chest wall,the distribution of target volume can be more uniform,which can reduce the exposure dose of heart and lung.