Chord-based image reconstruction from clinical projection data

Chord-based algorithms can eliminate cone-beam artifacts in images reconstructed from a clinical computed tomography (CT) scanner. The feasibility of using chord-based reconstruction algorithms was evaluated with three clinical CT projection data sets. The first projection data set was acquired using a clinical 64-channel CT scanner (Philips Brilliance 64) that consisted of an axial scan from a quality assurance phantom. Images were reconstructed using (1) a full-scan FDK algorithm, (2) a short-scan FDK algorithm, and (3) the chord-based backprojection filtration algorithm (BPF) using full-scan data. The BPF algorithm was capable of reproducing the morphology of the phantom quite well, but exhibited significantly less noise than the two FDK reconstructions as well as the reconstruction obtained from the clinical scanner. The second and third data sets were obtained from scans of a head phantom and a patient's thorax. For both of these data sets, the BPF reconstructions were comparable to the short-scan FDK reconstructions in terms of image quality., although sharper features were indistinct in the BPF reconstructions. This research demonstrates the feasibility of chord-based algorithms for reconstructing images from clinical CT projection data sets and provides a framework for implementing and testing algorithmic innovations.