女性蹲姿曲面模型光子外照射剂量研究

Research on photon external irradiation dosimetry for female squatting posture BREP phantom

基于中国女性参考人曲面模型建立女性蹲姿曲面模型,采用蒙特卡罗方法,针对6种标准光子外照射几何,计算光子能量0.01~10 Me V范围内21个能量点的器官吸收剂量转换系数和有效剂量转换系数,并与直立姿势的剂量数据进行了对比。结果表明：两种姿势中某些器官的吸收剂量转换系数在前后、后前以及侧向照射方式下差异较大。其中,后前照射方式下,光子能量为0.03 Me V时,乳腺的吸收剂量转换系数比直立姿势高115.1%。在不同照射方式下,大部分能量点的有效剂量转换系数的差异在10%范围内。转换系数的差异主要是由于胳膊和腿位置的改变,以及蹲姿时因身体前倾造成器官在照射方向上厚度发生改变而产生的。

By establishing female squatting posture BREP phantom based on Chinese reference female BREP phantom,this paper researched the effects of posture change to photon dose conversion coefficients. Using Monte Carlo methods,the organ dose conversion coefficients and the effective dose conversion coefficients of 21 monoenergetic photon beams from 0. 01 to 10 Me V under six standard irradiation geometries were calculated. Furthermore,the differences were compared between squatting and standing postures. It is found that there were greater differences among the organ absorbed dose conversion coefficients in anterior-posterior,posterior-anterior,left and right lateral irradiation geometries.For example,the absorbed dose conversion coefficient of breast is 115. 1% higher than standing position under posterior-anterior irradiation geometry at 0. 03 Me V. However,the differences of the effective dose conversion coefficients are within 10% in most energy points. The differences in conversion coefficients are due to the position of arms,legs and the thickness changes in irradiation direction of rays for squatting position.