Varian Clinac iX 15 MeV光子束能谱重建  

Reconstruction of 15MeV Photon Spectrum of Varian Clinac iX Linac

作　　者：陈元华[1] 周正东[1] 王东东[1] 

机构地区：[1]南京航空航天大学核科学与工程系,南京210016

出　　处：《中国医学物理学杂志》2013年第6期4503-4506,共4页Chinese Journal of Medical Physics

摘　　要：目的:精确重建Varian Clinac iX 15 MeV光子束能谱。方法:利用先验模型和遗传算法,以光子束中轴百分深度剂量(PDD)为基础数据实现医用直线加速器光子能谱重建。1.EGS模拟仿真Varian Clinac iX治疗头和标准水模体,获得15MeV光子束的模拟能谱以及单能光子中轴PDD数据;2.根据测量得到的中轴PDD数据以及模拟得到的单能光子中轴PDD数据,运用遗传算法优化求解先验模型的参数;3.将优化后的先验模型所计算的结果作为初始化种群,再用遗传算法二次优化重建光子能谱。结果:重建能谱与蒙特卡洛模拟得到的能谱具有良好的一致性,相关系数为0.9970;重建能谱的平均能量与由相空间文件分析所得平均能量的相对误差为1.16%;根据重建能谱计算得到的中轴PDD数据与实际测量的中轴PDD数据之间的相关系数为0.9999。结论:利用先验模型和遗传算法进行光子束能谱重建可靠有效,具有实用价值。Objective： To reconstruct 15 MeV photon beam＇s spectra of Varian Clinac iX accelerator precisely. Methods： The prior model and genetic algorithm were used to derive photon spectra from percentage depth dose （PDD） data of photon beam central axis. Firstly, the spectra of 15 MeV photon beams of Varian Clinac iX treatment head and PDD data of mono- energetic photon beams were calculated by Monte Carlo simulation. Secondly,the genetic algorithm was employed to optimize the parameters of the prior model according to both measured and simulated PDD data. Then, the obtained result was taken as initial population of the genetic algorithm to reconstruct photon spectra. Results：The reconstructed spectra is in good agreement with that calculated by Monte Carlo simulation, the correlation coefficient being 0.9970. The mean energy of reconstructed spectra is close to those derived from phase-space file, relative error of is about 1.16%. The derived PDD data calculated from the reconstructed spectra agree well with Monte Carlo simulated PDD data, and the correlation coefficient is 0.9999. Conclu- sions： The proposed method is reliable and effective for photon spectra reconstruction.

关 键 词：光子能谱 先验模型 遗传算法 百分深度剂量 蒙特卡罗模拟 

分 类 号：TP391[自动化与计算机技术—计算机应用技术]