SU‐F‐I‐08: CT Image Ring Artifact Reduction Based On Prior Image

Abstract

Purpose:In computed tomography (CT) system, CT images with ring artifacts will be reconstructed when some adjacent bins of detector don't work. The ring artifacts severely degrade CT image quality. We present a useful CT ring artifacts reduction based on projection data correction, aiming at estimating the missing data of projection data accurately, thus removing the ring artifacts of CT images.Methods:The method consists of ten steps: 1) Identification of abnormal pixel line in projection sinogram; 2) Linear interpolation within the pixel line of projection sinogram; 3) FBP reconstruction using interpolated projection data; 4) Filtering FBP image using mean filter; 5) Forwarding projection of filtered FBP image; 6) Subtraction forwarded projection from original projection; 7) Linear interpolation of abnormal pixel line area in the subtraction projection; 8) Adding the interpolated subtraction projection on the forwarded projection; 9) FBP reconstruction using corrected projection data; 10) Return to step 4 until the pre‐set iteration number is reached. The method is validated on simulated and real data to restore missing projection data and reconstruct ring artifact‐free CT images.Results:We have studied impact of amount of dead bins of CT detector on the accuracy of missing data estimation in projection sinogram. For the simulated case with a resolution of 256 by 256 Shepp‐Logan phantom, three iterations are sufficient to restore projection data and reconstruct ring artifact‐free images when the dead bins rating is under 30%. The dead‐bin‐induced artifacts are substantially reduced. More iteration number is needed to reconstruct satisfactory images while the rating of dead bins increases. Similar results were found for a real head phantom case.Conclusion:A practical CT image ring artifact correction scheme based on projection data is developed. This method can produce ring artifact‐free CT images feasibly and effectively.