1. A method of reconstructing x-ray tomographic images comprising data from a circular orbit and data from a linear orbit, based on a shadow zone formed by projecting data of the circular orbit, such method comprising the steps of: representing the image obtained from the circular orbit in a circular horn-shaped volume; representing the image obtained from the linear orbit in a corresponding linear horn-shaped volume; converting 2D images in the vertical planes of each said circular horn-shaped volume and each said linear horn-shaped volume into a plurality of 2D Fourier planes; removing projections of a 3D shadow cone in each of said 2D Fourier planes from the circular orbit data and replacing said projections with the corresponding projections obtained from the linear orbit data, so as to generate a plurality of repaired 2D Fourier planes; conducting an inverse 2D Fourier Transform on said plurality of repaired 2D Fourier planes to obtain a respective plurality of 2D image planes, representing a resulting horn-shaped volume; and converting said resulting horn-shaped volume back to the x-ray tomographic image.