Dual‐energy approach to reduce cone‐beam artefacts in a circular orbit cone‐beam CT system

The authors propose a dual‐energy approach to reduce cone‐beam artefacts in a circular orbit cone‐beam computed tomography (CT) system. When there exist multiple dense structures within a large cone angle, two‐pass algorithm is ineffective for reducing cone‐beam artefacts because high‐density materials are incorrectly segmented with simple thresholding. The proposed algorithm utilises projection data obtained with dual‐energy X‐ray spectra to estimate projections of the high‐density materials from multi‐density anatomical structures. Using bone and water as two of basis functions, the projection data of bone materials can be precisely estimated via dual‐energy scans. Then, bone‐only images are reconstructed by a constrained total‐variation minimisation‐based iterative algorithm. The reconstructed bone images are used to generate cone‐beam artefacts and the final corrected images are acquired by subtracting the generated cone‐beam artefacts from the original Feldkamp, Davis, and Kress images. The proposed method was validated using an extended cardiac‐torso phantom with complex vertebral anatomy and compared with the two‐pass algorithm. The results show that the proposed method restores distorted bony structures and intensity values, especially in regions with large cone angles. A qualitative evaluation of the mean‐squared errors and structural similarities demonstrates the effectiveness of the proposed method compared to the two‐pass algorithm.