Patent Number: 
Section: claims

1. A method for obtaining an x-ray image of a subject, comprising the steps:irradiating a subject with x-rays produced in an x-ray tube by emitting electrons from a cathode onto a focal spot on a surface of an anode while rotating the anode around a rotation axis to cause an x-ray beam to be emitted from said focal spot, said surface being inclined relative to said rotation axis and thereby causing said x-ray beam to have a varying image resolution/definition within said x-ray beam from a side of said x-ray beam facing said cathode to a side of said x-ray beam facing said anode, with an x-ray beam of highest image resolution/definition being at said side of said x-ray beam facing said anode;gating said x-ray beam to produce a fan-shaped x-ray beam therefrom;moving said fan-shaped x-ray beam through an examination region, containing said subject, substantially in a direction of the rotation axis of said rotary anode by tilting said x-ray tube relative to said focal spot to cause said fan-shaped x-ray beam to always to be gated from said region of highest image resolution/definition during movement of said fan-shaped x-ray beam through the examination region; anddetecting x-rays in said fan-shaped x-ray beam attenuated by said subject and generating an x-ray image of the subject therefrom. 2. A method as claimed in claim 1 comprising gating said x-ray beam with a slit-shaped diaphragm to produce said fan-shaped x-ray beam, and displacing said slit-shaped diaphragm through said examination region in said direction of said rotation axis synchronized with the movement of the fan-shaped x-ray beam through the examination region. 3. A method as claimed in claim 1 comprising gating said x-ray beam with a slit-shaped diaphragm having a displaceable opening therein to produce said fan-shaped x-ray beam, and displacing said opening within said slit-shaped diaphragm in said direction of said rotation axis synchronized with the movement of the fan-shaped x-ray beam through the examination region. 4. A method as claimed in claim 1 wherein said rotary anode has a radial direction associated therewith, and comprising controlling operation of said cathode to selectively enlarge a cross-section of said electron beam to enlarge said focal spot in said radial direction. 5. A method as claimed in claim 1 comprising rotating said x-ray tube around an axis proceeding through said focal spot and perpendicular to said examination region while moving said fan-shaped x-ray beam through said examination region. 6. A method as claimed in claim 5 wherein said axis is a first axis, and additionally rotating said x-ray tube around a second axis disposed in a plane of said fan-shaped x-ray beam and being perpendicular to said rotation axis, said second axis being disposed outside of said focal spot at a side of said focal spot facing away from said examination region. 7. A method as claimed in claim 1 comprising detecting said fan-shaped x-ray beam attenuated by said subject using a radiation detector comprising a detector row extending through only a portion of said examination region transverse to a direction of movement of said fan-shaped x-ray beam through said examination region, by electronically moving said detector row through said examination region. 8. A method as claimed in claim 7 comprising gating said x-ray beam with a slit-shaped diaphragm having a slit-opening with a center point to produce said fan-shaped x-ray beam, and wherein said detector row has a center point, and orienting said x-ray tube, said slit-shaped diaphragm and said detector row relative to each other to place said focal spot, said center point of said opening and said center point of said row detector on a straight line that is moveable through said examination region. 9. A method as claimed in claim 1 comprising gating said x-ray beam with a first slit-shaped diaphragm to produce said fan-shaped x-ray beam before said fan-shaped x-ray beam passes through said examination region, and detecting said fan-shaped x-ray beam attenuated by said subject with a radiation detector, and gating said fan-shaped x-ray beam with a second slit-shaped diaphragm disposed approximate said radiation detector, and moving said second slit-shaped diaphragm through said examination region in said direction of said rotation axis synchronized with the movement of said fan-shaped x-ray beam through said examination region. 10. A method as claimed in claim 1 comprising gating said x-ray beam with a slit-shaped diaphragm, comprising two diaphragm plates disposed opposite each other that define an opening that gates said x-ray beam, to produce said fan-shaped x-ray beam, and selectively moving said diaphragm plates toward and away from each other to selectively define a width of said opening, and thus a width of said fan-shaped x-ray beam. 11. A method as claimed in claim 10 comprising detecting said fan-shaped x-ray beam attenuated by said subject using a radiation detector and, in said radiation detector, converting the attenuated x-rays into an electrical image signal, and also detecting scatter radiation, associated with said fan-shaped x-ray beam, with said radiation detector, and automatically determining a ratio of said scatter radiation to radiation converted into said electrical image signal and controlling displacement of said diaphragm plates relative to each other to widen said opening as said ratio decreases and to narrow said opening as said ratio increases. 12. A method as claimed in claim 1 wherein said fan-shaped x-ray beam has a dose rate associated therewith, and comprising automatically calculating a radiation exposure to the subject in said examination region from said dose rate and comprising detecting said fan-shaped x-ray beam attenuated by said subject with a radiation detector and, in said radiation detector, converting the attenuated radiation into an electronic image signal representing an image having an image contrast associated therewith, and automatically controlling said dose rate dependent on said radiation exposure and said image contrast to increase said dose rate upon a low image contrast and to decrease said dose rate upon a high radiation exposure. 13. A method as claimed in claim 1 wherein said subject is a female breast, and comprising detecting said fan-shaped x-ray beam attenuated by said female breast using a radiation detector disposed in a support plate, and compressing said female breast between said support plate and a compression plate disposed above said support plate while moving said fan-shaped x-ray beam through said examination region.