Research On Local Reconstruction Algorithm Of Low Dose X-ray CT

The X-Ray computed tomography(CT)is one of the most commonly used methods in clinical diagnosis.It plays an important role in the early screening and follow-up diagnosis and treatment of diseases.However,conventional X-ray CT scanning is often accompanied by a high dose of radiation,which will cause certain harm to human body.Although the local scanning method can reduce the radiation dose,the quality of reconstructed images will be seriously reduced due to the truncation of projection data.Therefore,it is of great significance to study the local reconstruction correlation algorithm of low-dose X-ray CT.Based on this,this dissertation firstly summarizes the research status of local reconstruction algorithms at home and abroad,and analyzes the imaging characteristics of low-dose X-ray CT and local tomography,and then summarizes the characteristics and methods of reconstruction algorithms.Next,the algorithm improvement and optimization are focused on the truncation artifact reconstruction from local truncated projection data.The main research contents of this dissertation are as follows:(1)CT local reconstruction of sinusoidal image restoration based on hough transform.On the basis of analyzing the features of the projection data,the dissertation proposes to extract the sinusoidal structure information of the projection data by Hough transform and repair the truncated projection data by linear interpolation,and uses the FBP algorithm to reconstruct the local image.Experimental comparison shows that the algorithm can suppress the ring artifacts obviously and the reconstructed local image boundary is clear.(2)Sinusoidal graph repair combining line process and total variational model.The edge information of the truncated projection data detected by the line process model is used as the extended boundary.In the restoration process,aiming at the problem of missing data in the neighborhood of the pixels to be restored,pre-interpolation is carried out according to the distance ratio weighting of the known projection data,and then the projection data is repaired according to the total variational model.The effectiveness of the algorithm is verified by local reconstruction of simulation data and real data.(3)CT local reconstruction algorithm based on prior image-compressed sensing.Unlike truncation sinogram repaired right,determine place truncated data FBP algorithm to line process model reconstruction image position ring artifact,and according to the boundary information by using the variational model for smoothing,and the processed image as transcendental image of PICCS,finally,the ART-TVM reconstruction image and the position of the PICCS reconstruction image based on ring artifacts in image fusion.The local reconstruction of the simulated data shows that the proposed algorithm achieves a good balance in the aspects of artifact suppression and edge preservation.