1. A method for reconstructing an image of an object in a three-dimensional coordinate system with an x-ray computed tomography system, the method comprising the steps of: conducting a partial scan of the object by rotating an x-ray beam having a cone beam geometry around a portion of the object or rotating the object in the x-ray beam, the x-ray beam forming a scanning trajectory through a plurality of projection lines from a plurality of successive focal point locations; detecting the x-ray beam, attenuated by the object during the scan, to produce detector values; integrating the detector values along the projection lines to obtain intermediate data; and calculating three-dimensional Radon values representing substantially accurate or approximate plane integrals of the object from the intermediate data using a Grangeat relationship.