Approximate short-scan filtered-backprojection for helical CB reconstruction

Two approximate reconstruction algorithms are proposed for helical cone-beam CT. One involves rebinning of CB data into 2-D fan-beam sinograms, while the other one uses 3-D cone-beam backprojection. Both methods uses the short-scan idea of 2-D fan-beam CT to limit the obliqueness of the CB ray-sums involved in the reconstruction of each transaxial slice. Performances of the two algorithms are illustrated using the 3-D Shepp phantom and a disks phantom