北京大学学报（医学版）2018，Vol.50Issue(1)：131-135,5.DOI:10.3969/j.issn.1671-167X.2018.01.022
125I放射性粒子在骨介质中剂量分布的蒙特卡罗模拟
Simulation of dose distribution in bone medium of 125I photon emitting source with Monte Carlo method
摘要
Abstract
Objective: To present a theoretical analysis of how the presence of bone in interstitial brachytherapy affects dose rate distributions with MCNP4C Monte Carlo code and to prepare for the next clinical study on the dose distribution of interstitial brachytherapy in head and neck neoplasm. Methods: Type 6711,125I brachytherapy source was simulated with MCNP4C Monte Carlo code whose cross section library was DLC-200. The dose distribution along the transverse axis in water and dose constant were compared with the American Association of Physicists in Medicine (AAPM ) TG43UI update dosimetry formalism and current literature. The validated computer code was then applied to simple homogeneous bone tissue model to determine the affected different bone tissue had on dose distribution from 125I interstitial implant. Results: 125I brachytherapy source simulated with MCNP4C Monte Carlo code met the requirements of TG43UI report. Dose rate constant, 0. 977 78 cGy/(h · U), was in agreement within 1. 32％ compared with the recommended value of TG43UI. There was a good agreement between TG43UI about the dosimetric parameters at distances of 1 to 10 cm along the transverse axis of the 125I source established by MCNP4C and current published data. And the dose distribution of 125I photon emitting source in different bone tissue was calculated. Dose-deposition capacity of photons was in decreasing order: cortical bone, spongy bone, cartilage, yellow bone marrow, red bone marrow in the same medium depth. Photons deposited significantly in traversal axis among the phantom material of cortical bone and sponge bone relevant to the dose to water. In the medium depth of 0. 01 cm, 0. 1 cm, and 1 cm, the dose in the cortical bone was 12.90 times, 9.72 times, and 0.30 times of water respectively. Conclusion: This study build a 125I source model with MCNP4C Monte Carlo code, which is validated, and could be used in subsequent study. Dose distribution of photons in different bone medium is not the same as water,and its main energy deposits in bone medium surface,so we should consider the effect of bone medium when we design the target area adjacent to the bone tissue in 125I sources implantation plan.关键词
蒙特卡罗法/碘放射性同位素:骨/辐射剂量/近距离放射疗法Key words
Monte Carlo method/Iodine radioisotopes/Bone/Radiation dosage/Brachytherapy分类
医药卫生引用本文复制引用
叶克强,黄明伟,李君利,唐劲天,张建国..125I放射性粒子在骨介质中剂量分布的蒙特卡罗模拟[J].北京大学学报（医学版）,2018,50(1):131-135,5.基金项目
国家自然科学基金(81502652)资助 （81502652）
Supported by the National Natural Science Foundation of China (81502652) （81502652）
