Research On Key Techniques Of Cone-Beam CT Simulation System

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.