基于蒙特卡罗法的三源锥束X线CT散射和辐射剂量的分析

发布时间：2018-06-08 02:07

本文选题：蒙特卡罗 + 三源CT　；参考：《上海交通大学》2012年硕士论文

【摘要】：计算机断层成像技术（CT）是一种重要的医学成像技术，从诞生到现在的数十年的时间里经历了几代进步，仍在不断地发展和变革。自从2005年西门子公司率先推出了双源CT后，，多源CT的概念逐渐被人接受和认可。作为双源CT的延伸，三源CT将带来更快的数据采集速度和更高质量的重建图像，其精确重建算法也早已得到证明。作为评判CT设备性能的重要指标，散射和剂量是在CT研发中不可不考虑和研究的问题。散射带来的问题是使重建图像的值发生偏移，产生伪影或降低图像对比度，这些都会给医学诊断带来困难。而剂量则是涉及到辐射安全的问题。日益增加的医疗检测辐射问题使得放射安全和防护的重要性显得更加突出，设备给受检者带来的辐射剂量水平是每一台CT研制中都要考虑的。因此本论文就这两个问题，通过基于蒙特卡罗法的仿真技术，构建出虚拟的三源锥束X线CT系统，分析和研究了三源CT的散射和剂量情况。本文的主要内容包括：在开源蒙特卡罗仿真工具EGSnrc的基础上开发了CT仿真系统SimProj。该软件可根据需要定制系统结构、扫描的方式、轨迹、物理参数等，具备很强的扩展性和复用性；通过对三源锥束CT的仿真，我们分析了在不同锥角下散射光强的变化，比较了由各个光源引起的散射光及其引起的图像质量问题，对重建值偏移、图像对比度等问题做了量化的分析；对三源CT扫描数字人体模型的辐射剂量分析发现，尽管增加了两套影像系统同时工作，但是由于扫描方式的改变，三源CT和单源CT在扫描等距离范围时，对人体产生的辐射剂量是等量的。这些研究成果为三源CT的实际研发提供了帮助，同时也是为今后的仿真研究奠定了基础。
[Abstract]:Computed Tomography (CT) is an important medical imaging technology, which has undergone several generations of progress from its birth to now, and is still developing and reforming. Since Siemens introduced dual source CT in 2005, the concept of multi-source CT has been accepted and accepted. As an extension of dual-source CT, three-source CT will bring faster data acquisition speed and higher quality reconstruction image, and its accurate reconstruction algorithm has been proved. As an important index to evaluate the performance of CT equipment, scattering and dose are important problems in CT research and development. The problem of scattering is to offset the reconstructed image, produce artifacts or reduce the contrast of the image, which will bring difficulties to medical diagnosis. The dose is related to the problem of radiation safety. The increasing medical detection radiation problem makes the importance of radiation safety and protection more prominent. The radiation dose level brought by the equipment to the examinees is considered in every CT development. Therefore, in this paper, a virtual three-source cone-beam X-ray CT system is constructed based on Monte Carlo simulation technology, and the scattering and dose of three-source CT are analyzed and studied. The main contents of this paper are as follows: a CT simulation system SimProj. based on the open source Monte Carlo simulation tool EGSnrc is developed. The software can customize the system structure, scanning mode, trajectory, physical parameters and so on according to the need, and has strong expansibility and reusability. Through the simulation of three-source cone beam CT, we analyze the variation of scattering light intensity at different cone angles. The scattering light caused by each light source and the image quality problems caused by each light source are compared, the reconstruction value offset and image contrast are analyzed quantitatively, and the radiation dose analysis of three source CT scanning digital human body model is found. Although two sets of imaging systems are added to work simultaneously, due to the change of scanning mode, the radiation dose produced by three-source CT and single-source CT is equal to that of human body in the same range of scanning distance. These results are helpful for the practical research and development of three source CT, and also lay a foundation for future simulation research.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R142

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