Camgöz B, Yeğin G, Kumru M N
Ege University Institute of Nuclear Sciences, Izmir, Turkey.
Celal Bayar Univesity Science Faculty-Physics Depatment, Manisa, Turkey.
Rep Pract Oncol Radiother. 2010 May 26;15(3):69-74. doi: 10.1016/j.rpor.2010.04.003. eCollection 2010.
This work provides an improvement of the approach using Monte Carlo simulation for the Amersham Model 6711 (125)I brachytherapy seed source, which is well known by many theoretical and experimental studies. The source which has simple geometry was researched with respect to criteria of AAPM Tg-43 Report. The approach offered by this study involves determination of differential dose contributions that come from virtual partitions of a massive radioactive element of the studied source to a total dose at analytical calculation point. Some brachytherapy seeds contain multi-radioactive elements so the dose at any point is a total of separate doses from each element. It is momentous to know well the angular and radial dose distributions around the source that is located in cancerous tissue for clinical treatments. Interior geometry of a source is effective on dose characteristics of a distribution. Dose information of inner geometrical structure of a brachytherapy source cannot be acquired by experimental methods because of limits of physical material and geometry in the healthy tissue, so Monte Carlo simulation is a required approach of the study. EGSnrc Monte Carlo simulation software was used. In the design of a simulation, the radioactive source was divided into 10 rings, partitioned but not separate from each other. All differential sources were simulated for dose calculation, and the shape of dose distribution was determined comparatively distribution of a single-complete source. In this work anisotropy function was examined also mathematically.
这项工作改进了使用蒙特卡罗模拟法处理安捷伦6711型（125）碘近距离治疗籽源的方法，许多理论和实验研究都熟知该籽源。针对美国医学物理师协会（AAPM）Tg - 43报告的标准，对这种几何结构简单的籽源进行了研究。本研究提出的方法涉及确定来自被研究籽源的大量放射性元素的虚拟分区对分析计算点处总剂量的微分剂量贡献。一些近距离治疗籽源含有多种放射性元素，因此任何一点的剂量都是各元素单独剂量的总和。对于临床治疗而言，充分了解位于癌组织中的籽源周围的角向和径向剂量分布非常重要。籽源的内部几何结构对剂量分布特征有影响。由于健康组织中物理材料和几何结构的限制，无法通过实验方法获取近距离治疗籽源内部几何结构的剂量信息，因此蒙特卡罗模拟是本研究所需的方法。使用了EGSnrc蒙特卡罗模拟软件。在模拟设计中，将放射性源划分为10个环，这些环相互分隔但不分离。对所有微分源进行剂量计算模拟，并与单个完整源的剂量分布进行比较，以确定剂量分布的形状。在这项工作中，还从数学角度研究了各向异性函数。
