Spatial resolution enhancement in CT iterative reconstruction

Iterative reconstruction (IR) has recently been proposed to improve multiple aspects of image quality over conventional filtered backprojection (FBP) in X-ray computed tomography (CT). FBP reconstruction and its corresponding reconstruction kernels have been optimized for decades to provide the best possible image quality. IR does not have the notion of reconstruction kernels but uses other mechanisms to change the image resolution and image noise. This paper presents one computationally efficient technique to enhance the spatial resolution of IR images reconstructed from high resolution scans, based on the introduction of an enlarged voxel footprint in the forward model, combined with a band-suppression filter designed to eliminate any undesirable over- or under-shoot artifacts that may arise from the use of the enlarged voxels. The proposed technique achieves higher spatial resolution than high resolution FBP with significantly lower noise. Results are shown on both phantom and clinical patient data.