The Application Research On Statistical Reconstruction In X-ray Computed Tomography

Medical image system, especially X-ray CT, has been widely used for clinical diagnoses. It is fast and can get high quality image, so it is very popular in many hospitals. However, X-ray will cause great damage and the quality of image will be poor when reduce dose, which restrains its applications.We can get high quality images through statistical reconstruction when there are serious noises with the projective signal. So statistical reconstruction can be sued to reduce dose further. But because of much iteration, it cannot get real time images. As a result, it will restrain fast character of X-ray CT. Accelerating statistical reconstruction and applications in X-ray CT are research directionsThis thesis introduced the basic theories of X-ray CT, the basic concept of reconstruction and discussed the theories, methods, and result of statistical reconstruction used in X-ray CT reconstruction. As to the projection and reconstruction program, VC++ (Visual C++) was used for programming in this thesis. The main contents of this research are as follows:From the Filtered Back Projection algorithms, the theory of CT imaging were discussed; Introduced the statistical reconstruction algorithm, discussed and elaborated on the difficulty of statistical reconstruction used in X-ray CT; Reduced disk storage and increased iterative speed through introducing polar grids model; Achieved more accurate system matrix using weighting factor according to density of X-ray; Enhanced the convergence characteristic by combining the ordered subset algorithm and the complete ordered subset algorithm with a relaxation factor; Analyzed and evaluated the result of reconstruction.The innovations in this dissertation are as follows:Applied the polar grids model to statistical reconstruction, reduced disk storage and increased iterative speed; Combined the ordered subset algorithm and the complete ordered subset algorithm with a relaxation factor to enhance convergence characteristic of statistical reconstruction; Developed a method of introducing weighting factor to area system matrix for getting more accurate system matrix in fan beam X-ray CT; Wrote program for reconstruction with VC++.