质子治疗中靶区定位的蒙卡模拟

发布时间：2018-12-21 13:40

【摘要】：自质子治疗概念提出以来,质子放疗技术得到了广泛的关注并迅速地发展。精确放疗是当前的主流方向,其中“精确定位”的实现是精确放疗的良好开端,被更多的研究者所关注。目前,对靶区定位的在线监测一般采用湮灭伽马射线成像的方式。然而这种方式的定位偏差在几毫米甚至到厘米量级,误差较大,因此对“精确定位”提出了更高要求。近年来蒙特卡罗方法已成为医学研究中方案设计及优化的一种最常用手段,本文利用此方法对质子治疗中产生的湮灭光子进行图像重建,提出一种新的定位方式,极大地提高了定位的精准度。质子与人体中~(16)O反应生成正电子核素13N,衰变后释放的正电子与体内电子发生湮灭反应生成光子。通过追踪光子的位置和质子在路径上的能量沉积这两个信息进行靶区定位。本文利用MCNPX程序进行建模计算,模拟了能量为60 MeV-150 Me V的质子束在肌肉组织中的输运及能量为90 Me V的质子束在不同材料的GTV(肿瘤靶区)中的输运,讨论分析了质子入射能量及GTV材料对湮灭光子分布的影响。提出“湮灭光子峰”概念,定义湮灭光子通量下降梯度最大的位置为湮灭光子峰位置。重建湮灭光子通量一阶导数的图像,评估峰位置,模拟结果显示湮灭光子峰位置与Bragg峰位置相差无几,位置偏差小于1 mm,定位精准度高。本工作在验证新定位方式可行性的同时也为后续精准定位的研究提供了参考数据。
[Abstract]:Since the concept of proton therapy was put forward, proton radiotherapy technology has been widely concerned and developed rapidly. Accurate radiotherapy is the mainstream direction at present, and the realization of accurate positioning is a good beginning of accurate radiotherapy, which has been paid more attention by researchers. At present, annihilation gamma-ray imaging is generally used to monitor the target location on-line. However, the positioning deviation of this way is in the order of several millimeters or even to centimeters, and the error is large, so the "accurate positioning" is required higher. In recent years, Monte Carlo method has become one of the most commonly used methods in the design and optimization of medical schemes. In this paper, we use this method to reconstruct the image of annihilation photons produced in proton therapy, and propose a new localization method. The accuracy of positioning is greatly improved. Proton reacts with ~ (16) O to form positron 13N, and the released positron is annihilated with in vivo electrons to form photons. The target is located by tracking the position of the photon and the energy deposition of the proton on the path. In this paper, the transport of proton beam with energy of 60 MeV-150 Me V in muscle tissue and proton beam with energy of 90 Me V in GTV (tumor target region) of different materials are simulated by MCNPX program. The effects of proton incident energy and GTV material on the annihilation photon distribution are discussed and analyzed. The concept of "annihilation photon peak" is put forward, and the position of annihilation photon peak is defined as the position where the maximum drop gradient of annihilation photon flux is obtained. The image of the first derivative of annihilation photon flux is reconstructed and the peak position is evaluated. The simulation results show that the position of the annihilation photon peak is almost the same as that of the Bragg peak, and the position deviation is less than 1 mm,. This work not only verifies the feasibility of the new positioning method, but also provides reference data for the further research of precise positioning.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R815

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