Development of a new three-dimensional image reconstruction algorithm to reduce cone-beam artifacts

We investigated an image reconstruction algorithm to reduce cone-beam artifacts in cone-beam CT. To examine the factors involved in the occurrence of cone-beam artifacts, micro-spheres phantom were arranged longitudinally at different positions and a computer simulation was performed. Due to differences in projection angle, data projected onto the detector surface were projected along trajectories shown as different periodic functions depending on the distance and position from the center of rotation. Therefore, projection along several detector channels based on different projection data resulting from different periodic functions is considered responsible for the increase in cone-beam artifacts associated with an increase in the distance of reconstruction planes from the center of rotation. Our new algorithm to reduce such artifacts features: 1) A change in weighting with respect to projection data obtained at different projection angles. 2) Distribution of correction coefficients so that they are larger near the center of the detector, while taking individual channel data for the detector into account, and smaller near the edges. 3) Three-dimensional backprojection of corrected projection data. The effect of the reduction in cone-beam artifacts of an object located at the edges markedly enhanced reconstruction planes at positions further from the center of rotation.