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研究医用电子直线加速器产生的9MeV电子束和6MV-X射线对乳腺癌放射治疗时靶外组织的受照剂量,探讨减少靶外组织受照剂量的方法,为临床优化治疗计划提供剂量学依据。借助非均匀组织等效拟人体模型,模拟乳腺癌放射治疗,处方剂量是胸壁照射总剂量50 Gy、淋巴引流区域照射总剂量60 Gy,每次照射2.0 Gy;采用GR-200A LiF(Mg,Cu,P)TLD,将TLD预置于照射野外所关心的组织或器官中作间接剂量测量。在胸壁照射区域,以9 MeV电子束单独照射时,靶外组织剂量从29.0cGy到295.5cGy;以6MV—X射线单独照射时,靶外组织剂量从32.0 cGy到206.7 cGy;在淋巴引流区域,6MV-X射线照射时靶外组织剂量从22.5 cGy到1650.9 cGy。阴影屏蔽可使电子束造成的靶外组织剂量下降9.4％～53.6％,使X射线造成的靶外组织剂量下降19.7％～56.6％;接触屏蔽可使X射线对靶外组织的剂量贡献下降44.2％～65.6％。胸壁照射采用电子束与X射线的混合比为2:3的照射比单纯用电子束或X射线照射可使靶外高剂量组的组织或器官的受照剂量明显下降。
To study the doses of 9MeV electron beam and 6MV-X rays produced by medical electron linear accelerators for the target tissue during radiation therapy for breast cancer, and to explore ways to reduce the dose of irradiated tissues outside the target, so as to provide dosimetric basis for optimizing clinical treatment plans. Using a non-uniform tissue-equivalent manikin model to simulate breast cancer radiation therapy, the prescribed dose is a total dose of chest wall irradiation of 50 Gy, a total dose of 60 Gy in the lymphatic drainage area, and 2.0 Gy per irradiation; GR-200A LiF (Mg, Cu) P) TLD, TLDs are pre-positioned in tissues or organs of interest outside the irradiated field for indirect dose measurement. In the chest wall irradiation area, when the 9 MeV electron beam was irradiated alone, the target tissue dose was from 29.0 cGy to 295.5 cGy; when irradiated with 6MV-X rays alone, the target tissue dose was from 32.0 cGy to 206.7 cGy; in the lymphatic drainage area, The dose of off-target tissue at 6MV-X irradiation ranged from 22.5 cGy to 1650.9 cGy. Shadow shielding can reduce the dose of extra-target tissue caused by electron beam by 9.4% to 53.6%, and decrease the dose of extra-target tissue caused by X-ray by 19.7% to 56.6%; contact shielding can reduce the dose contribution of X-ray to target tissue 44.2 %~65.6%. Chest wall irradiation with a 2:3 ratio of electron beam to X-ray radiation is significantly lower than the irradiation dose of tissues or organs outside the target high-dose group compared with electron beam or X-ray irradiation alone.