角度变化对乳腺癌术后电子线放疗剂量分布影响研究

目的 探讨照射角度变化对乳腺癌术后电子线放疗剂量分布的影响。方法 使用仿真人体组织等效模型模拟典型成年女子左侧乳腺癌术后患者,以6 MeV电子束进行术后模拟照射,靶区单次照射2 Gy,选取350°、355°、0°、5°、10°五个角度作为照射角度,使用热释光剂量片测量靶区胸壁及敏感器官的剂量分布。结果 选取350°、355°、0°、5°、10°五个角度后,胸壁受照剂量没有明显变化,其中胸壁两侧部位在355°旋转时受照剂量变化差异高于中间部位,但差异无统计学意义(t=1.418,P > 0.05);敏感器官受照剂量有明显变化,其中对照组患侧肺、健侧肺受照剂量为(0.79±0.15) Gy和(0.21 ±0.08) Gy,5°旋转角度组患侧肺、健侧肺受照剂量为(1.06 ±0.23) Gy和(0.31 ±0.11) Gy,差异有统计学意义(t=2.42,t=3.14,P < 0.05)。结论 乳腺癌术后电子线放疗过程中,不同照射角度变化降低靶区边缘受照剂量,并在旋转5°时明显增加了患侧肺和对侧肺的受照剂量,临床摆位中值得注意。

The Dosimetric Effect of the Angle Change after Electron Beam Irradiation for the Patients after Breast Surgery

Objective To study the dosimetric effect of the rotational angle change after electron beam irradiation after breast surgery.Methods The standard manikins model was used to simulate the female patients'left breast cancer, and was irradiated by 6 MeV electron beam at the horizontal position. The irradiatves dosimetry of target was 2 Gy. The irradiation was set 350°、355°、0°、5°、10° rotational angle change and applied 0.5 mm tissue equivalent bolus. Thermoluminescence dose meters was used to measure the dosimetric effect of chest wall, two lungs and heart.Results After set 350°、355°、0°、5°、10° rotational angle change, the dose of chest wall had no significant change. The dose change of chest wall in two sides at 355° and 5°rotational was higher than that of the middle parts, but the differences have no significant change(t=1.418,P > 0.05); sensitive organs had significant change, the dose of the same lung and the contralateral lung in control group was(0.79 ±0.15) Gy and(0.21 ±0.08) Gy, and in 5° rotational angle change group was(1.06 ±0.23) Gy and(0.31 ±0.11) Gy,the differences have significant change(t=2.42,t=3.14,P < 0.05).Conclusion In the process of electron beam irradiation for the patients with breast cancer, the rotational angle change degrades the dosimetric coverage of target organs' edge, and the 5° rotational angle change increases dosimetric coverage in the same lung and the contralateral lung.