The Research On Algorithms Of Image Reconstruction And Artifact Corrections Based On Prior Information

X-ray computerized tomography(CT)is has been widely used in many domains such as diagnosis medicine,non-destructive detection in industry etc.The actual reconstruction images,have lots of prior information,such as prior image related to reconstruction image,except for sparsity.X-ray phase-contrast imaging(PCI)is an emerging technique that utilizes a new imaging mechanism that provides high contrast and high resolution of biological soft tissues.Combined with computed tomography(CT),PCI has been successfully extended to CT mode recently,resulting in X-ray phase-contrast computed tomography(PCCT),which enables the visualization of the interior features within the samples non-invasively.Thus,PCCT has high research value and broad applications in the biomedical imaging.In this paper,we research a new CT image reconstruction technique based on guided image filtering.?an image enhancement technique and ring artifacts correction technique based on PCCT.The main contributions and innovations are listed as follows:(1)The challenge of computed tomography is to reconstruct high-quality images from few-view projections.To solve this,using a prior guidance image,guided image filtering smoothes images while preserving edge features.The prior guidance image can be incorporated into the image reconstruction process.We propose a new simultaneous algebraic reconstruction technique based on guided image filtering to improve image quality.To validate the algorithm practicality and efficiency,experiments were performed with numerical phantom projection data and real projection data.The results demonstrate that the proposed method is effective and efficient.(2)PCI combined with CT has been playing an important role in the structural investigation of biology samples.However,the biologic samples image with lower or uneven contrast is obtained invariably.In order to solve the problem,the interval mapping algorithm between FBP and SART is proposed,it is used as the basis for the content adaptive image detail enhancement.The results show that the method can not only reduce background noise but also enhance the image and get a higher contrast for real section synchrotron data.(3)CT reconstructed images are affected by a number of different artifacts.Although some of them(i.e.motion artifacts,beam hardening)are avoided or reduced thanks to the high degree of monochromatic radiation provided by synchrotron facilities,ring artifacts affect also synchrotron XPCT images.In this paper,a novel method ring artifacts correction was presented based on combining TV-L1 model with guided image filtering(GIF)in the reconstruction image domain.To validate the performance of this method,simulation data and real experimental synchrotron data are provided.The results demonstrate that TV-L1 model with GIF step can effectively correct ring artifacts for IL-PC-CT.(4)We develop an IL-PC-CT reconstruction method based on anisotropic total variation(TV)minimization.Numerical demonstrations of anisotropic TV algorithm are performed with real synchrotron data,the results show that SART-anisotropic TV reconstructs the liver features more precisely than both SART and SART-isotropic TV.Using this method,the ring artifacts are corrected during the reconstruction process.The correction results show that the proposed method can reduce visible ring artifacts while preserving the liver section details for real liver section synchrotron data.