9MeV电子线照射技术治疗乳腺癌术后胸壁靶区的方案比较

目的：分析9 MeV电子线照射乳腺癌根治术后胸壁靶区的剂量学分布特点。方法：以椭圆柱型调强体模上模拟人体胸壁靶区，分别设计5种治疗方案：①单野垂直照射；②单野30度照射；③两野照射,机架角度15°和43°；④三野照射,机架角度为15°、30°和43°；⑤模拟拉弧照射,机架角度从15°到44°，每度一个射野。比较各计划剂量分布，肺V20，PTV 95%，Dmax以及高量图。结果：单野垂直照射剂量分布呈楔形分布。5种方案PTV 95%分别为：4172 cGy、4885 cGy、4923 cGy、4911 cGy、4900 cGy；肺V20分别为：14.23%、18.00%、17.82%、17.91%、17.93%；Dmax分别为：6081 cGy、6400 cGy、5661 cGy、5620 cGy、5598 cGy。结论：增加射野数目和变换射野入射方向是优化电子线治疗计划的2个有效手段。针对乳腺癌根治术后胸壁靶区PTV形状狭窄，弧度大且包绕肺面积广的病案，建议实施三野夹角电子线照射。

Comparison of irradiation plannings on postmastectomy chest wall target with 9 MeV electron beam

Objective：To analyze the characteristics of postmastectomy chest wall irradiation with 9 MeV electron beam. Methods：On IMRT phantom, five radiation plannings were designed with 9 MeV electron beam： ①single-field vertllal planning; ②single-field planning with the gantry of 30°;③double-field planning with the gantry of 15° and 43°; ④triple-field planning with the gantry of 15°,30°and 43°; ⑤simulate-arc planning with the gantry from 15° to 43°.Then the dose distribution, lung-V 20, PTV 95%and Dmax were compared. Results： The dose distribution of the single-field veryical planning were cuneate.For the 5 plannings, the lung-V20 were 4172 cGy、4885 cGy、4923 cGy、4911 cGy and 4900 cGy,the PTV95% were：14.23%, 18.00%、17.82%、17.91% and 17.93%,and the Dmax were 6081cGy、6400cGy, 5661 cGy,5620cGy and 5598cGy respectively. Conclusion： Increasing the field number and changing the incidence direction were the effective means to optimize the electron beam radiation planning and the triple-field planning was suitable for the paitent whose chest wall target was both narrow and long around the lung.