A post-processing method for improving contrast and reducing cupping artifacts in low-energy CBCT images

X-ray scattering in the cone beam computed tomography system can lead to undesirable reduction in contrast and overall image quality of reconstructed images. The scatters inside the object cause a serious problem, especially when the object is large and contains a lot of materials, such as bones and soft tissues. In this paper, the amount of X-ray scattering is numerically estimated using the Monte Carlo method based on the GEANT4 software. A new procedure that employs the numerical result to improve the contrast and the overall quality of the actual reconstructed images produced by a prototype dental CBCT system is introduced. The procedure has been primarily tested on various simple geometry CT objects, and found to be able to improve the contrast and the cupping artifacts of the reconstructed images. Further analysis also shows that the calculated CT numbers of the materials derived from the corrected image are more in line with the documented values than those from the uncorrected one.