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为了准确地获得直线加速器的光子能谱,根据测量的百分深度剂量和蒙特卡洛模拟的单能光子百分深度剂量,采用先验约束模型和遗传算法来进行优化求解.首先,将光子能谱建模为一个包含2个参数α和Ep的先验解析函数,采用遗传算法对该模型进行优化求解;然后,将光子能谱建模为一个离散约束优化模型,并利用遗传算法进行优化求解,初始解由第1步获得的解析函数产生.将该方法应用于瓦里安iX直线加速器来计算其6和15 MV光子束的能谱,实验结果表明,采用该方法重建获得的光子能谱以及百分深度剂量与蒙特卡洛模拟计算的结果具有良好的一致性.
In order to obtain the photon spectrum of the linear accelerator accurately, a priori constraint model and genetic algorithm are used to optimize the solution based on the measured percent depth dose and the Monte-Carlo simulation of single-energy photon depth fraction.Firstly, the photon energy The model is modeled as a priori analytic function containing two parameters α and Ep, and the genetic algorithm is used to optimize the model. Then, the photon energy spectrum is modeled as a discrete constrained optimization model and optimized by using genetic algorithm , The initial solution is generated from the analytic function obtained in step 1. This method is applied to the Varian iX linear accelerator to calculate the energy spectra of its 6 and 15 MV photon beams. The experimental results show that this method can reconstruct the photon spectrum As well as the percentage depth of dose and Monte Carlo simulation results have good consistency.