Research On CT Image Reconstruction Algorithm At Low Dose

Computed Tomography(CT)imaging technology has many advantages,such as painless,non-invasive,clear pathological development,low cost and so on.Nowadays,CT has become a modern technology which was applied widely in the field of clinical diagnosis and treatment.However,due to the security risks of high X-ray scanning dose,it has gradually attracted people's attention.The quality assurance of CT scan imaging at low doses has become a practical problem that needs to be solved urgently in clinical applications.The decrease of radiation dose of X-ray is easy to lead to poor imaging quality,which will affect the clinical diagnosis results of doctors.Therefore,reducing the CT scan dose as much as possible on the premise of meeting the image quality standard has important scientific research value and clinical practical value.Based on the principle of CT technology,this paper studies the statistical iterative reconstruction algorithm under low-dose scanning.The main work of this paper is as follows:(1)Penalized Weighted Least-Squares(PWLS)algorithm will have a great noise effect in low-dose scan reconstruction,and TV(Total Variation)regularization processing can achieve a better noise reduction effect.Therefore,Therefore,this paper designs a PWLS-TV(PWLSTotal Variation)CT reconstruction algorithm,which performs TV regularization on the basis of PWLS algorithm.The analysis and reconstruction FBP(Filter Back Projection)algorithm is combined with the statistical iterative algorithm.The FBP algorithm is used to preprocess the initial image estimation,and then the statistical iterative algorithm is used for reconstruction.The results of simulation and physical experiments show that the PWLS-TV algorithm is better than the PWLS algorithm in reconstructing images.(2)The traditional reconstruction method is based on pixel reconstruction.This paper fuses the pixels one by one to obtain the neighborhood block patch,and then proposes a patch-based PWLS-PR(PWLS-Patch based Regularization)algorithm.Traditional pixel-based reconstruction methods cannot accurately distinguish the edge structure and noise fluctuations of the image when there is noise.The neighborhood patch method is to obtain more image features through the calculation of the entire domain block.In addition to the edge preservation feature,it can also maintain the features or textures in the neighborhood block.Simulation and physical experiment results show that the PWLS-PR algorithm not only can effectively suppress artifacts and better preserve edge characteristics and image detail structure information when reconstruction at low doses,but also can achieve noise reduction.The reconstruction quality of images is better than PWLS and PWLS-TV algorithms at low doses.(3)The interface of CT image reconstruction system is designed for users.The system interface provides three algorithms: PWLS,PWLS-TV,and PWLS-PR to realize image reconstruction.After logging in,the user can select the corresponding algorithm and set the parameters as needed,then read in the image and display the reconstructed image result.The system provides users with a platform with friendly interface,simple operation and complete functions.