Research On CT Image Reconstruction And Artifact Correction Algorithm

Computed tomography(CT)has the advantages of fast scanning speed and high imaging resolution,and can obtain the internal structure information of the object under examination without damaging it,which is widely used in medical clinical diagnosis and industrial nondestructive testing.However,due to the current technical means,it is difficult to achieve ideal data acquisition and projection reconstruction,which leads to various artifacts in the final CT images and affects the subsequent analysis and processing.Therefore,it is of great theoretical significance and practical value to study how to suppress CT image artifacts and improve image quality.The paper investigates the cone beam artifacts,windmill artifacts and metal artifacts that appear in CT images,and the main research work is as follows:(1)A spiral FDK(Feldkamp-Davis-Kress)reconstruction algorithm based on three-dimensional weighting and two-domain filtering is proposed for the cone-beam artifact and windmill artifact problems in spiral CT.The 3D weighted spiral FDK algorithm suppresses cone beam artifacts by giving unfavorable weights to rays with large cone angles,and the improved dual-domain filtering algorithm can remove windmill artifacts while retaining more details.The results of computer simulation experiments show that the algorithm can effectively suppress cone beam artifacts and windmill artifacts in the reconstructed images and improve the quality of CT images.(2)A normalized metal artifact correction algorithm based on top-hat operation and anisotropic diffusion filtering is proposed for the metal artifact problem in CT reconstructed images.The top-hat operation can recover the loss of skeletal structure caused by linear interpolation,and the anisotropic diffusion filtering has the effect of preserving the image edge details and reducing the noise,which can remove the residual artifacts in the image and thus obtain better quality a priori images.The experimental results show that the proposed algorithm can effectively reduce metal artifacts and avoid introducing secondary artifacts,while preserving the bone and fine structures around the metal implants compared with the classical metal artifact correction algorithm.(3)Aiming at the problem of residual artifacts in the general CT image metal artifact correction algorithm,a metal artifact correction algorithm based on directional total variation(DTV)is introduced,which calculates the TV of CT images from multiple directions,then solves the DTV using a gradient descent algorithm,and uses a projection domain iterative algorithm for artifact correction to improve the effectiveness of the TV algorithm.The effectiveness of the algorithm is verified by simulation experiments and practical experiments.