A method reconstructs a reconstruction data set containing virtual X-ray images of projection images of a target region recorded with an X-ray device. The projection images being recorded at different positions of an X-ray source along a scanning trajectory. The method includes defining an imaginary position of the X-ray source for each virtual X-ray image. For each virtual X-ray image and each pixel to be reconstructed in the X-ray image a virtual beam section, covering the target region, of the path between the imaginary position of the X-ray source and the pixel is defined. For each projection image, an integral is determined from the relationships between the forward projection and the filtered back-projection by re-parameterizing. A projection value of the virtual X-ray image from the integrals determined is combined.