Image-reconstruction algorithm based on constrained conjugate gradient for radiography

Based on the constrained conjugate gradient algorithm, a regularization preconditioned constrained conjugate gradient algorithm (RPCCG) was proposed for image-reconstruction for radiography. The RPCCG used the Tikhonov regularization criterions to get the reconstruction equation. The equation was solved by using the preconditioned conjugate gradient algorithm, constrained with prior knowledge. Numerical experiment results show that in comparison with the FBP algorithm, RPCCG based on least square + smoothness criterion is more efficient in reconstruction quality and noise removal.