125I粒子治疗舌下腺恶性肿瘤的靶区剂量分布研究

目的 测量并计算¹²⁵I放射性粒子治疗舌下腺恶性肿瘤的放射剂量在口底靶区及靶区周缘黏膜、颌骨、皮肤等组织器官的分布,为临床治疗提供客观依据.方法 利用仿生物人体模型进行实验,分别使用活度为29.6、25.9 MBq/粒的¹²⁵I放射性粒子31粒,处方剂量(即周缘匹配剂量)120 Gy,模拟对单侧舌下腺恶性肿瘤进行组织间植入近距离放疗,采用热释光剂量计测量并计算口底靶区及周围组织器官的剂量值,采用辐射自显影胶片绘制剂量分布曲线.结果 靶区中心剂量达到390~500 Gy,靶区边缘剂量达到160~480 Gy,靶区边缘外1 cm剂量达到90~170 Gy.皮肤的接受剂量为25~81 Gy,下颌骨靶区外的接受剂量为7.9~67 Gy.靶区内剂量分布无明显冷区.结论 ¹²⁵I放射性粒子治疗口底区舌下腺恶性肿瘤,可以达到有效的靶区内治疗剂量分布.对周围组织的放射剂量在安全限值以下.对下颌骨的放射剂量较小,减少了放射性骨损伤的可能.

Study of dose distribution of sublingual gland carcinoma treating with 125I radioactive seeds

Objective To measure and calculate the dose distribution (tissue absorbed dose) of mouth floor area while using ¹²⁵I to treat sublingual gland carcinoma.Methods Phantom of head and neck was used to place the ¹²⁵I radioactive seeds to simulate the sublingual gland carcinoma treatment. ¹²⁵I radioactive seeds of 29.6 and 25.9 MBq per seed were used as two groups, with 31 seeds in each group, and prescribed dose (peripheral matched dose) was 120 Gy. Thermoluminescence dosimetry (TLD) was used to measure the absorbed dose value in the simulated target and adjacent area. Gafchromic Eriochrome Black T (EBT) film was used to draw the dose distribution curve.Results Dose absorbed in the target area, target area center and the adjacent area one centimeter away from target reached 160 Gy, 390-500 Gy, and 90-170 Gy, respectively. Dose of the skin ranged from 25 to 81 Gy, dose of mandible ranged from 7.9 to 67 Gy. No radiation cold spot was found.Conclusions ¹²⁵I seeds could achieve an effective therapeutic dose distribution of the target area for sublingual gland carcinoma. Dose absorbed in the adjacent tissue is under safety limit. The radiation dose at mandible is lower, reducing the possibility of radiation damage to the bone.