Ring Artifacts Elimination Method in Computed Tomography using Sparsity-Induced Norms

Ring artifacts degrade the visibility of computed tomography images, where they appear as concentric circles in the reconstructed image. They are usually generated due to some limitations/failure associated with imaging hardware. Ring artifacts may destruct effective information in the image, and hence they should be carefully identified and eliminated without damaging other image structures. In this paper, we propose a ring artifacts elimination method that works within the image reconstruction process. With the existence of ring artifacts, the projection data can be represented as a sum of two components. The first contains perfect ideal projection data and the second contains imperfect elements causing the ring artifacts. We propose to minimize sparsity-induced norms such as a combination of ℓ
0
and ℓ
1
-norms of the imperfect elements to remove the ring artifacts efficiently. The proposed algorithm is generated through optimizing the cost function with the alternative direction method of multipliers. The efficiency of the proposed method is tested qualitatively and quantitatively using simulation studies. Results of the reconstructed images show significant elimination of the artifacts.