左乳癌根治术后胸壁电子线与X线和电子线混合照射的剂量学研究

Dosimetric Study on the Electron Beam Irradiation and the Mixed Irradiation of X-ray and Electron Beam 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X线和电子线混合照射的剂量学特点。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、X线和电子线混合照射两组计划,比较两种放疗计划的剂量学参数。结果:X+E计划D_(min)、D_(mean)、V_(90)、V_(95)、V_(100)升高,差异有统计学意义(P<0.05);D_(max)、V_(105)和V_(110)降低,其中D_(max)和V_(110)差异均有统计学意义(P<0.05);CI和D_(95)升高、D_5降低,差异均有统计学意义(P<0.05);危及器官左肺V_5、V_(10)、V_(15)、V_(20)、V_(30)、V_(40)和D_(mean)X+E计划低于E计划,差异均有统计学意义(P<0.05);右肺D_(mean)X+E计划稍高于E计划,差异无统计学意义(P>0.05);X+E计划心脏V_5、V_(10)、V_(15)、V_(20)和D_(mean)总体呈下降趋势,其中V_5、V_(10)、V_(15)差异均有统计学意义(P<0.05),V_(30)和V_(40)虽有升高但差异无统计学意义(P>0.05)。结论:X+E计划的靶区剂量分布和对患侧肺和心脏,尤其是对心脏低剂量体积保护优于E计划;并且胸壁表面垫0.5 cm厚的等效填充物既可使靶区剂量分布更加均匀又进一步降低了心肺的受照剂量。

Objective To compare the dosimetric characteristics of electron beam irradiation and the mixed irradiation of X - ray and electron beam on the chest wall for patients receiving left - sided modified radical mastectomy. Method 10 patients who had received left - sided modified radical mastectomy were enrolled. The pinnacle 3 9. 6 planning system was adopted to design two treatment plans on the chest wall,respectively,which were the electron beam irradiation （E plan） and the mixed irradiation of X - ray and electron beam （ X ＋ E plan） ; and the dosimetric parameters of the two radiotherapy plans were compared. Results In the X ＋ E plan, the minimal dose （ Dmin） , mean dose （ Dmean） , and the Dmean and percentage of volume receiving more than 90 Gy （V90）,95 Gy （ V95） and 100 Gy （ V100） irradiation were increased , with the differences being statistically significant （P 〈 0. 05） ;the maximal dose （Dmax） ,as well as the Dmean and percentage of volume receiving more than 105 Gy （V105） and 110 Gy （V110） irradiation were decreased,with the differences in Dmax and V110 being of statistical significance （P 〈0. 05） ; the conformi-ty index （Cl） and the dose of 95% CTV （ D95） were increased, while the dose of 5 % CTV （ D5） were reduced, and all the differences were statistically significant （P 〈0. 05）. With regard to the organs at risk,the V5, V10, V20 ,V30, V40 and Dmean of the left lung in the X ＋ E plan were lower than those in the E plan,with the differences being of statistical significance（P 〈0. 05）; the Dmean in the right lung was slightly higher in the X ＋ E plan than in the E plan,but the difference was of no statistical signifi-cance （P 〉 0. 05 ）. The V5, V10, V15, V20 and Dmean in the heart in the X ＋ E plan showed a decreasing trend on the whole, among which,the differences in the V5 ,V10 and V15 were of statistical significance （P 〈0. 05） ,while the V30 and V40 were increased, but the difference were of no statistical significance （P 〉 0. 05 ）. Conclusion The X ＋ E plan has more significant advantages over the E plan on the dose distribution of target volume and the protection of heart and lung in the affected side, especially on the low dose volume protection of heart. By using the 0. 5 cm - in - thickness equivalent filler upon the chest wall, the distribution of tar-get volume could be more uniform, which could reduce the exposure dose of heart and lung.