Ct Image Variational Model Of Ring Artifact Removal

CT technology not only is able to show the structure relation and defect status of object interior details accurately and clearly, but also can quantitatively give the radiation density data and material composition. So it is widely applied in medical illness diagnoses and industrial defect recognition and property measurement. Because of the advantages of rapid scanning, the third generations scanning mode has become dominating in MCT and ICT fields. As one of the important problems of the third generations scanning mode, ring artifacts not only effect the image quality, but also hamper subsequent processing, such as image noise processing, image segmentation, and so on. Finally, image recognition ability and measurement accuracy is reduced. This problem is particularly outstanding in ICT imaging system. Therefore, ring artifact removing is the key step to precorrection of CT images.The ring artifact correction algorithms were proposed based on the sinogram by majority of scholars. Coordinate transformation is used by two times for the ring artifact correction algorithms based on the reconstruction images. high-pass filter was adopted to filter original projection data and reduce artifact information. ring artifact correction algorithms of this paper were proposed based on merits of the PDE, which is used the model of Variational model to correcte the ring artifact. The ring artifact correction algorithms can reduce the fault which is used by two times Coordinate transformation, because the ring artifact was corrected by the algorithms based on the reconstruction images.The main works are in the following areas:First, I describe the theoretical basis of the variational model for image processing, and the principle of its fast Split Bregman iterative algorithm. The Split Bregman algorithm is came true by transforming variational problems into simple Poisson equations and precise soft thresholding formulas through introducing an auxiliary variable. Second, I introduce the PDE method of contrast enhancement function, and design a region-based segmentation stretch function Third, I propose an energy function of the variational models of gradient, divergence, and the contrast enhancement function. Then I design the Split-Bregman, algorithm of the energy functional, and design a program through C and OpenCv library.The method introduced in this article is to remove the ring artifacts in the reconstructed image directly. A large number of experimental comparisons show that the variational model proposed in this article can effectively remove the ring artifacts in CT images, while maintaining image detail and contrast of the image.