Application Research On Several New Technologies Of Computed Tomography

Computerized Tomography as a technique to accurately and intuitively display the internal structure of objects has been widely used in clinical applications and industrial inspection. Particularly in the medical field, it plays an irreplaceable role. However, with clinical requirements getting higher, traditional absorption-based CT has begun to show limitations in imaging of certain matter, such as light elements or matter with same attenuation values and so on. Therefore, it is of great significance to develop a new imaging technique.Phase contrast imaging techniques could solve problems that imaging of light elements. Phase contrast CT is able to get high contrast images of certain sample according to the change of its phase information after x-ray passed through. Among all existing phase contrast imaging methods, grating-based differential phase contrast CT (DPC-CT) is the most promising one in clinical use for it could use conventional x-ray. However, DPC-CT hits its bottleneck when applied to clinical use for it has a major problem in terms of radiation dose. In response to the problems above, this paper presents a DPC-CT iterative image reconstruction algorithm——DD-L1, which combines CS theory with CT iterative reconstruction technique and introduces distance driven forward and backward projection computation strategy. The experimental results show that DD-L1algorithm can generate tomographic images of higher quality even when the projection data is incomplete, so the method is helpful to promoting the process of DPC-CT stepping into clinical applications.Dual energy CT (DECT) can accurately reconstruct effective atomic number and electron density image so that matter with same attenuation values can be distinguished. The mainstream DECT is preprocessing reconstruction algorithm, in which projection decomposition is the key step. Given the traditional projection decomposition algorithm inefficiency of speed and complexity of computation, this paper uses a projection decomposition algorithm based on projection matching algorithm. Besides, there are another two problems in DECT image reconstructing:first, real dual-energy projection data is difficult to obtain; second, the current research work on complete numerical simulation method of DECT image reconstructing has not yet been reported. Therefore, this paper presents a simulation method to perform numerical simulations for every part of projection decomposition algorithm and then dual-energy reconstruction is completed. The results of the simulation method show its effectiveness and reliability, proving that such a method can benefit the development of dual-energy imaging technology.In addition, although phase contrast imaging technique has achieved considerable success, it remains difficult to be applied in clinical use due to its rather stringent experimental conditions and process. Optical theory indicates that there is a liner relationship between phase term and electron density. Therefore, in this paper, phase contrast imaging method based on DECT is proposed. And this research is helpful to promoting phase contrast imaging technique stepping into clinical applications.