Improved 2D rebinning of helical cone-beam CT data using John´s equation

This paper describes a method to improve the accuracy of the rebinning algorithms for helical cone-beam CT. Rebinning algorithms separate the 3D field-of-view into independent oblique slices. Each ray-sum in the sinogram of an oblique slice is approximated by a measured ray-sum that diverges from the helix segment. Because the measured ray-sum does not generally lie within the oblique slice, the method is approximate. John´s partial differential equation is a consistency condition for the 3D X-ray transform. We show how John´s equation can be used to compute a first order correction to the advanced single slice rebinning algorithm. The improved rebinning algorithm is evaluated using simulated data.