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Nonlinear Deviation CorrecTion for Ring-Artifact Removal With Cone-Beam Computed Tomography

In practice, cone-beam computed tomography (CT) images are usually tarnished by ring artifacts. To address this problem, in this article, we proposed a ring-artifact removal technique based on the nonlinear deviation correction of pixel response for flat panel detector (FPD), named Nonlinear Deviation CorrecTion (NDCT). Our proposed NDCT is a two-point fitting correction method of the local response from mean projection images. Its advantages lie in the following three aspects. First, it obtains correction coefficients by solving the correction equations based on the mean projection images without additional scanning, which improves efficiency. Second, it corrects all pixels of FPD at the same time, which eliminates the inconsistency of adjacent pixels and then the ring artifact within the 3-D CT image can be corrected. Third, the calculation is very simple so the correction speed is fast, which further improves efficiency in practice. Both numerical and real experiments showed that our NDCT method achieved excellent performance and fast speed in ring-artifact removal.