颅脑肿瘤放射治疗时射野外器官吸收剂量体模法测量与分析

Test and analysis of out-of-field organ dose in intracranial tumor radiotherapy using phantom

目的：在是否使用楔形板和照射野面积不同的情况下，测量和分析颅脑肿瘤放射治疗时射野外器官的吸收剂量。方法使用中国成人男性仿真人体模型，模拟颅脑肿瘤放射治疗，采用不使用楔形板的普通方野照射技术组和使用楔形板的三维适形照射技术（3D-CRT）组，普通方野照射技术组分别用2 cm×2 cm野和4 cm×4 cm野进行照射，3D-CRT组分别按等效方野面积分为2 cm×2 cm野和4 cm×4 cm野进行照射；使用热释光剂量计测量射野外器官的吸收剂量并进行分析。结果颅脑肿瘤靶区处方剂量为100 cGy时，射野外各器官吸收剂量范围为0．13-2．83 mGy。头颈部器官4 cm×4 cm野照射时的吸收剂量与2 cm×2 cm野比较，差异有统计学意义（t=-5．023， P=0．004）；胸腹部器官4 cm×4 cm野照射时的吸收剂量与2 cm×2 cm野比较，差异无统计学意义（t=-1．438， P=0．171）。普通方野照射组头颈部器官、腹部器官的吸收剂量与3D-CRT组比较，差异均有统计学意义（t 头=-2．805， P=0．038；t腹=-11．966，P=0．000）。结论接受颅脑肿瘤放射治疗的患者，射野外器官吸收剂量的大小与照射野面积、是否采用楔形板照射技术有关。接受大野照射的患者，靶区邻近器官吸收剂量越大；照射野面积和处方剂量相同时，使用楔形板的照射技术相对于不使用楔形板的射野外器官的吸收剂量增大。

Objective To test and analyze out-of-field organ dose in intracranial tumor radiotherapy with or without wedges and in different radiation field areas. Methods The absorbed doses of out-of-field organs were measured using a thermoluminescent dosimeter by intracranial tumor radiotherapy simulation in the domestic phantom. The tests were grouped according to radiation field areas and techniques. Common square field techniques do not use wedges, whereas 3D conformal radiotherapy（3D-CRT） uses wedges. The radiation field area was divided into 2 cm × 2 cm and 4 cm × 4 cm fields. Results The absorbed doses of out-of-field organs ranged from 0.13 mGy to 2.83 mGy per 100 cGy prescription dose. The doses of organs adjacent to the target area are higher after irradiation using the 4 cm × 4 cm field than after irradiation using the 2 cm × 2 cm field（t=-5.023, P=0.004）;however, no statistically significant（t=-1.438, P=0.171） difference can be found in organs non-adjacent to the target area. The doses of organs are higher after irradiation using 3D-CRT with a wedge than after irradiation using common square field techniques without a wedge regardless of whether the organs are adjacent to the target area or not （t 头=-2.805, P=0.038;t 腹=-11.966, P=0.000）. Conclusions The absorbed doses of out-of-field organs of the＆amp;nbsp;patients who received intracranial tumor radiotherapy are associated with radiation field areas and techniques. The doses of organs adjacent to the target area increase as the radiation field area increases in size. Given a uniform radiation field area and prescription dose, the absorbed doses of out-of-field organs irradiated by radiotherapy techniques with wedges are higher than those of organs irradiated by radiotherapy techniques without wedges.