The Research On Reconstruction Image Quality Improvement Of Large Cone Angle CT Scans

Cone beam computed tomography is a kind of equipment which utilizing different algorithm to reconstruct the whole 3D image through X-ray projection of different angles.Cone beam CT attracts much more attention because of its high efficiency and higher reconstruction image distinguishability.Filter backprojection algorithm(FDK)is an important algorithm of circular trajectory cone beam CT reconstruction.Because the FDK algorithm can realize accurate reconstruction image quality in the center plane.it also has a reasonable reconstruction image quality in the case of small angle,it has much significant implications.But,with the increasing angle and lacking of data,it will cause reconstruction image quality decreasing and artifacts enlargement.Based on the original FDK algorithm,using of cone angle weighting function to improve original FDK algorithm which can establish a relationship between cone angle and reconstructed point can weight points in the other planes except the center plane to decrease the artifacts.Then making a simulation experiment based on Shepp-Logan model with 30 degree cone angle reduces artifacts effectively.In addition,this article proposes an algorithm based on concentric double trajectory FDK algorithm,which means two different radiuses of circular scans.Then utilizing this results to corrects reconstruction image quality though probabilistic calculation.Subsequently,making a simulation of 30 degree cone angle and comparing with the original FDK reconstruction image,it can prove the modified FDK algorithm has a better reconstruction image quality.Finally,in view of the CT reconstruction filter function;this article presents a mixed filter function.And making free noise and noise simulations respectively,compared with R-L filter function.S-L filter function and cosine filter function.based on the value of criterion of mean square distance criterion,absolute distance and image similarity coefficient,it can be considered that the mixed filler function can restrain noise and increase reconstruction image quality effectively(In the case of noise conditions,the mixed filter function can improve the effect of noise inhibition).