CT ring artifact reduction using an improved wavelet filtering in the sinogram domain

OBJECTIVE: Ring artifacts often appear in flat-panel detector-based CT images due to the malfunction or mis-calibration of the detector elements that result in stripe artifacts in the line integral projection (sinogram) data. The ring artifacts lower the image quality and affect image-based diagnoses. Here we propose a ring artifacts removal approach based on wavelet filtering in the sinogram domain. The line integral projection (sinogram) dataset were divided into 4 sub-sinogram dataset, and for each of them the wavelet decomposition operation was employed to produce the associated wavelet dataset, followed by filtering operation on the vertical detail band and the low-pass detail band. Wavelet reconstruction operation was then performed, and the weighted moving average filter was used to yield the filtered sinogram, which was processed using filtered back-projection (FBP) for image reconstruction. The results showed that the proposed approach could effectively remove the ring artifacts while preserving the structural information of the image.