Cone-beam reconstruction by backprojection and filtering

A new analytical method for tomographic image reconstruction from cone-beam projections acquired on the source orbits lying on a cylinder is presented . By application of a weighted cone-beam backprojection, the reconstruction problem is reduced to an image-restoration problem characterized by a shif t-variant point-spread function that is given analytically. Assuming that t he source is relatively far from the imaged object, a formula for an approx imate shift-invariant inverse filter is derived; the filter is presented in the Fourier domain. Results of numerical experiments with circular and hel ical orbits are considered. (C) 2000 Optical Society of America [S0740-3232 (00)01111-X].