WE-G-217BCD-10: Shading Correction in Image Domain for Cone-Beam CT Without Prior Information

Medical Physics
Qiyong FanLei Zhu

Abstract

Cone-beam CT (CBCT) images contain severe shading artifacts mostly due to scatter. Many algorithms have been proposed to alleviate this problem by data correction on projections. Sophisticated methods have also been designed to further improve the image quality when prior patient information is available. In this work, we develop a novel algorithm for shading correction directly on CBCT images without any prior information. In CBCT, projection errors (mostly scatter) result in dominant low-frequency shading artifacts in image domain. Due to circular scan geometry, these artifacts often show global or local radial patterns. We first convert the uncorrected images into the polar coordinate system. Median filtering and polynomial fitting are applied on the transformed images to accurately estimate the low-frequency bias field of shading angle-by-angle and slice-by-slice. The estimated bias field is then converted back to the Cartesian coordinate system, followed by 3D low-pass filtering to eliminate possible high-frequency components. The shading-corrected images are finally obtained as the uncorrected volume divided by the shading bias field. The proposed algorithm has been evaluated on CBCT images of a pelvis patient and a head ...Continue Reading

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