【作者】 黄魁东；

【导师】 张定华；

【作者基本信息】 西北工业大学 ， 航空宇航制造工程， 2006， 硕士

【摘要】 锥束CT利用面阵探测器获取物体的二维射线投影,并通过三维重建得到物体在扫描体积范围内的所有切片图象。它与传统的二维CT相比,具有扫描速度快、空间分辨率高和射线利用率高等优点,在工业无损检测和医学应用领域中都有广阔的应用前景,是当今国际CT研究领域的前沿课题之一。 锥束CT仿真是锥束CT研究的重要内容。本文重点研究了锥束CT仿真系统的数学建模、STL样本模型投影成像的并行快速仿真等关键技术,开发构建了一个支持混合样本、非点光源与多光谱投影仿真的锥束CT仿真系统平台。 主要研究内容和成果如下: 1.锥束CT仿真系统的数学建模。在分析X射线与物质的相互作用及其衰减规律的基础上,研究了锥束CT成像的物理原理。根据计算机仿真的一般模型和锥束CT系统的组成,提出了基于光线跟踪和X射线衰减定律的投影成像仿真总体思路。完成了射线源、探测器和检测样本等主要部件的数学建模,实现了通用锥束CT仿真系统的装配,并给出了投影仿真计算的算法流程。 2.STL样本模型投影成像的并行快速仿真。针对STL样本基元,根据锥束CT仿真投影的特点,研究了一套基于八叉树的锥束CT仿真投影快速计算方法。采用SIMD技术对投影计算中的关键部分进行并行计算,进一步提高了生成仿真投影图象的速度。实验结果表明,在保证投影图象精度的前提下,该方法较之于UG样本投影计算有60～90倍左右的加速比,极大地提高了锥束CT仿真投影的计算速度,增强了仿真系统的实用性。 3.锥束CT仿真系统平台研发。面向锥束CT仿真研究需求,研究了锥束CT仿真软件系统的功能划分、体系结构、系统数据模型、系统框架设计和组件集成方法。在集成CSG、UG、STL、Voxel四种样本独立仿真功能模块的基础上,提出并实现了混合检测样本的建模方法与仿真技术,开发了一个支持混合样本、非点光源与多光谱的锥束CT仿真系统;通过三个实例系统地验证了本文研究成果的有效性,为进一步开展锥束CT技术研究,提供了一个良好的研究开发和实验平台。更多还原

【Abstract】 Cone-beam CT refers to a technique for imaging all cross-sections of an object using 3D image reconstruction algorithms based on a series of X-ray projections captured by an area detector from different angles around the object. Owing to the advantages of faster scanning speed, higher spatial resolution and better utilization of X-ray photons compared with traditional 2D CT, cone-beam CT has a broad application perspective in industrial non-destructive testing and medical applications, and is an advanced research topic in the current international CT community.Cone-beam CT simulation is an important part of cone-beam CT research. The dissertation mainly studied the key techniques which are the mathematics modeling of cone-beam CT simulation system, and the parallel rapid simulation of the projection imaging with STL phantom models. Then a cone-beam CT simulation system platform was developed, which provided the projection simulation for compounding phantoms, non-point X-ray source and multiple X-ray spectrums.The main research contents and achievements are articulated as follows:1. Mathematics modeling of cone-beam CT simulation system. Based on analysing the interaction with substances and the attenuation law of X-ray, the physical principle of cone-beam CT imaging was studied. According to the common model of computer simulation and the structure of cone-beam CT system, a whole design of projection imaging simulation based on ray-tracing and on the X-ray attenuation law was proposed. The mathematics modelings for main components, including X-ray source, detector and phantom, were accomplished. After achieving the assembly of universal cone-beam CT simulation system, the algorithm flow of projection simulated computation was presented.2. parallel rapid simulation of the projection imaging with STL phantom models. In respect that the properties of cone-beam CT simulated projection, a suite of rapid algorithms based on octree was studied for STL phantom models. By parallely computing the key parts in the projection calculation with SIMD technique, the speed of creating simulated projection images was more heightened. The experimental result shows that the algorithms achieve a speedup of 60-90 times than UG phantom projection without any image quality loss, which greatly enhance the computed speed of cone-beam CT simulated projection and intensify the practicality of the simulation system.3. Research and develop the Cone-beam CT simulation system phantom. Aiming at the cone-beam CT simulation research requirement, the function partition, system architecture and data model of cone-beam CT simulation software system were studied, as well as general framework and component integration method. The modeling method and simulation technique of compounding phantoms were brought forward and realized based on integrating the independence simulation function models of CSG, UG, STL and voxel phantoms. Then a cone-beam CT simulation system was developed, which provided the projection simulation for compounding phantoms, non-point X-ray source and multiple X-ray spectrums. All the research achievements were tested and verified systematically by using three instances in the system. The simulation system provides a favorable experimental platform for further research and application of cone-beam CT.更多还原