光子射野剂量计算参数研究  

The Study of Parameters for Photon Beam Dose Calculations

作　　者：刘胜堂[1] 顾熹豪[1] 文万信[1] 

机构地区：[1]苏州大学医学部放射医学与防护学院江苏省放射医学与防护重点实验室,苏州215123

出　　处：《中国医学物理学杂志》2014年第2期4723-4726,4755,共5页Chinese Journal of Medical Physics

基　　金：江苏高校优势学科建设工程资助项目(PADD);江苏省环保科技项目(201020)

摘　　要：目的:介绍医用加速器常规光子射线的机器数据测量方法及剂量计算模型中基本参数的计算过程。以百分深度剂量与散射因子为基础数据,根据原散射线模型通过测量数据推导出原射线组织最大剂量比、散射最大剂量比、原射线在水中线性衰减系数、能量注量等,为进一步还原射野在水模体中的剂量分布提供方法与理论。方法:用Blue Phantom三维水箱在医科达Synergy加速器上测量6 MV光子线的百分深度剂量、离轴比剂量、总散射因子、准直器散射因子,先从测量的百分深度剂量曲线中按照原散射模型剥离出原射线百分深度剂量,然后在Matlab软件中拟合处理测量的散射因子数据,外推出零野的模体散射因子,从而按照给定公式计算出组织最大剂量比、散射最大剂量比。按照离轴比剂量,利用平方反比规律推出最大开野在模体表面的能量注量。结果:计算出准直器散射因子、总散射因子的拟合公式,外推零野模体散射因子(Sp)、根据原射线的百分深度剂量曲线计算出原射线在水中线性衰减系数,组织最大剂量比(TMR)、散射最大剂量比(SMR)、以及射野能量注量分布(Fluence Matrix)。结论:这些基本参数是剂量计算建模的关键,也是进一步研究各种剂量计算模型的基础。Objective： To introduce basic measurement methods of linear accelerator＇s photon beam parameters and process of data for photon beam dose calculations model.According to measured primary depth dose and sactter factor based on primary and scatter model we calculate primary depth dose and tissue maximum ratio,sactter maximum ratio,attenuation factor and flu- ence matrix,thus give method for redistribution of beam dose in water phantom. Methods： IBA Bule Phantom is chosen as mea- suring. We fixed it under Elekta＇s Synergy linear accelerator and the 6 MV X-ray was used and fiunaly we got the percent depth dose, off axis dose, scatter factor of all selected beams.We first substract primary percent depth dose from those beams percent depth dose, and then make exponent function fit for total sactter factor and collimator sactter factor, so zero beam＇s phantom sactter factor can be derived from fit results.Finally fluence matrix can be calculated from offset axis ratio dose using law of in verse squares. All works would be processed with Matlab. Results： Exponent function fit results of total scatter factor, collimator scatter factor, extapolation zero field phantom scatter factor will be showed after calculated, primary percentage depth dose ,Tis sue-Maximum Ratio,Scatter-Maxmum Ratio and fluence matrix were calculated with all selected beam percent depth dose and offset axis ratio dose. Conclusions： Those parameters play important part role in dose calculate models and algorithms,and make the foundation for further study in various kinds photon beam dose calculation models.

关 键 词：光子射野参数 原射线百分深度剂量 能量注量 

分 类 号：R811.1[医药卫生—放射医学]