Feature-Sensitive Ring Artifact Correction for Computed Tomography

In computed tomography (CT) reconstruction, ring artifacts emerge from incorrectly normalized or defective detector elements. Correction algorithms often introduce blur or do not correctly accommodate the behaviour of those artifacts. Normalization errors stem from noise in the detector images during the normalization process and are always present to some degree. We propose a method for correcting ring artifacts from incorrectly normalized detector elements in the sinogram. Our approach compensates for errors both in the individual gain as well as offset of pixel values. We reduce blur by inferring gain and offset information for each pixel from its neighbors only in a subset of all projections. We show with datasets from real measurments that our method is effective at mitigating the shortcomings of purely offset based approaches and approaches using all projections. Furthermore, our method can be efficiently implemented compensating for most overhead times. Under usual circumstances, our method can be implemented to function with no additional time overhead at all.