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伽玛刀作为一种聚焦式的放射治疗设备,是立体定向放射外科的一个重要分支。它能将放射源(绝大部分为60Co)发出的伽玛射线几何聚焦,集中射于病灶,一次性、致死性地摧毁靶点内的组织。在对伽玛刀进行放射治疗剂量学研究时,一般有3种手段:实验方法测量、解析方法计算和蒙特卡罗方法计算。其中蒙特卡罗方法对放射疗法计划的作用早已被医学物理学界明确认识[1],加拿大国家研究委员会的Bielajew[2]指出,在放射治疗中,往往需要在较短时间内得出剂量场分布,而过去蒙特卡罗方法由于太消耗机时显得力不从心。近些年来,计算机运算速度的提升、蒙特卡罗算法的优化和减小方差技巧的开发,使得快速蒙特卡罗计算成为了可能[3-4]。本研究将针对我国自主生产的某型伽玛刀,利用蒙特卡罗核粒子输运程序(Monte Carlo N-Particle Transport Code,MCNP)系统建立一套快速、准确的剂量场分布蒙特卡罗算法模型,通过对比实验结果证明模型结果的准确性。并利用所建立的模型对伽玛刀剂量场特性进行研究,为改进伽玛刀的设计以及提高临床剂量估计的精度提供一定依据。
基于蒙特卡罗算法模拟的某型伽玛刀剂量场特性研究
Dose field characteristics study of Gamma knife based on Monte Carlo simulation
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摘要:
目的 针对我国自主生产的某型伽玛刀,建立一套快速、准确的蒙特卡罗算法模型,并利用所建立的模型对伽玛刀剂量场特性进行研究。 方法 利用蒙特卡罗核粒子输运程序建立伽玛刀的蒙特卡罗算法模型,并用实验结果对模拟结果进行验证。 结果 离轴比:和实验结果符合良好,随着准直器孔径的减小,顶部剂量率平台随之减小,半影区也有减小的趋势但不明显;等剂量曲线:旋转轴垂直平面上的剂量梯度最小。 结论 (1)所建立蒙特卡罗算法模型是准确有效的;(2)在制定治疗计划时,需要考虑到肿瘤和体表距离、肿瘤大小、形状以及射野不均匀性带来的影响。 -
关键词:
- 伽玛刀 /
- Monte Carlo方法 /
- 剂量场特性
Abstract:Objective To build a Monte Carlo model of a type of gamma knife independently produced in China, and prove the accuracy of this model and study dose field characteristics of the gamma knife. Methods Monte Carlo model was built based on Monte Carlo N-Particle Transport Code, and the simulation result was verified by the experiment results. Results Off Axis Ratio:the simulation result of Off Axis Ratios was in good agreement with the experiment results, the top dose rate platform decreased with the radium of the collimators reduced, penumbra decreased to some degree but not obviously; isodose curves:the dose gradient of the plane perpendicular to rotate axis was minimum. Conclusions (1) The Monte Carlo model was accurate and effective. (2)The distance between the tumor and body surface, the size, shape of the tumor and the heterogeneity of exposure field need to be considered when the treatment plan is developed. -
Key words:
- Gamma knife /
- Monte Carlo method /
- dose field characteristics
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