【作者】 周金斌；

【导师】 李国丽；

【作者基本信息】 合肥工业大学 ， 电工理论与新技术， 2008， 硕士

【摘要】 剂量计算是放射治疗计划系统(TPS,Treatment Planning System)的核心模块,其计算精度直接影响放射物理师制定治疗计划的质量。快速高精度剂量计算方法的研究始终是放疗计划系统研究的主要内容之一。三维适形调强放疗(IMRT,Intensity Modulated Radiation Therapy)逆向治疗计划中,精确、快速、可计算小截面照射束的剂量分布,是对剂量计算模型的基本要求。蒙特卡罗(MC,Monte Carlo)剂量计算程序在放射治疗医学领域,被公认为是模拟粒子输运的最强有力的工具,但由于其收敛速度慢、计算模拟时间长的致命弱点,目前仅能作为一些先进治疗计划系统的计划验证工具。随着三维适形调强放疗需求的不断增长和计算机运行速度的飞速发展,TPS系统对于剂量计算工具的速度和精度的要求也越来越高,因此改进和发展快速精确的剂量计算方法对精确放疗计划系统具有十分重要的意义。本论文开展了基于Monte Carlo模拟的矩阵模型fsPB(finite size PencilBeam)算法研究,利用Monte Carlo模拟有限笔束的剂量分布,并对不同入射角度的有限笔束的剂量分布数据进行直接矩阵存储,完全束的剂量分布基于原始数据的叠加得到。基于若干典型算例,比较分析了本算法计算结果与MonteCarlo直接模拟的实际剂量分布,并进行了误差分析,结果表明本算法的计算精度和速度达到预期效果。Batho组织不均匀性修正方法可以将纯水模中的剂量分布修正为人体中的剂量分布,方法是根据病人医学影像(例如CT)中的组织密度分布信息计算出修正因子。本文在以上基于Monte Carlo模拟的矩阵模型fsPB算法研究的基础上,编程实现了基于Batho修正的快速有限笔束算法,以水肺水模型为算例,用蒙特卡罗程序EGS4的计算结果为参考标准,对算法的计算结果进行了比较分析,表明了算法的实用性,为IMRT逆向计划过程提供了更多算法选择。更多还原

【Abstract】 Dose calculation plays a vital role in a radiotherapy treatment planning system(RTS), whose precision has great influence upon the quality of the therapy plan druw up by radiation physicists. The research on fast and accurate dose calculation method is always one of the main contents of the RTS research work. Accurate, fast, quantifiable small section of the beam irradiation dose distribution is the basic requirements for IMRT dose calculation model in IMRT Treatment Plan System.Monte Carlo method is a stochastic arithmetic, which can accurately simulate particle transport in radiation therapy process and obtain the rigor dose result. Whereas its extensive application in clinic radiotherapy plan is limited for consuming too much time. With the continuous growth of demand on Intensity Modulated Radiation Therapy and the rapid development of computer speed, TPS system needs more rapid and accurate dose algorithm. Therefore improving and developing a fast and accurate method of dose calculation for Accurate Radiation Therapy System is of great significance.A finite-size Pencil Beam algorithm of matrix model based on Monte Carlo procedure was presented. The dose distribution of a series of finite size pencil beams with different incident angles simulated by Monte Carlo code were directly stored as matrix. The full beam dose distribution would be obtained by direct superposing. Some test examples including both regular and irregular field were verified by this algorithm with Monte Carlo simulation. Results showed that it can satisfy the requirement in accuracy and speed for IMRT TPS.The Batho inhomogeneity correction can modify the dose distribution of pure water to human body by the patient medical images like CT. Based on the resrarch of matrix model fsPB algorithm, the Batho inhomogeneity correction method is programmed, tested by the water-lung-water examples, compared with the result of the EGS simulation, which provides more choice for the dose calculation algorithm for IMRT TPS.更多还原