A computed tomography system with an adjustable focal spot-to-detector distance has a gantry provided with a patient opening, an x-ray tube and a detector, respectively mounted at opposite sides of the gantry. The x-ray tube has a focal spot and the x-ray fan beam radiated from the focal spot exhibits a fixed aperture angle. The x-ray tube is installed on a linear track and can be moved along the rail of the linear track.