A computer tomograph (1) for mammographic x-ray imaging includes a MBFEX tube (20) and a flat-bed x-ray detector (30). Cathodes (40) are arranged in a fixed manner in rows in the MBFEX tube (20), the cathodes (40) being provided for the field emission of electrons. Geometry, radiation density and wavelength range of an x-ray beam (b) can be set. The MBFEX tube (20) is movable parallel (z) to the flat-bed x-ray detector (30). The flat bed x-ray detector (30) includes a moveable x-ray screen (31), the opening of which can be set. Using the x-ray screen (31), an imaging area (A) on the detector surface (D) of the flat-bed x-ray detector (30) can be selected and moved. Compared to conventional computer tomographs having rotating x-ray components, the computer tomograph (1) has a lighter and more compact design, with which a particularly small focal spot size is achieved.
