Patent Number: 
Section: claims

1. An X-ray diagnostic apparatus, comprising:a tabletop configured to support a subject;an X-ray tube configured to irradiate X-rays and disposed on one side of the tabletop;an X-ray detector configured to detect X-rays that penetrate the subject and disposed on the other side of the tabletop;four diaphragm blade units located between the X-ray tube and the tabletop, a first pair of diaphragm blade units configured to move antithetically in a longer direction of the tabletop, and a second pair of diaphragm blade units configured to move antithetically in a shorter direction of the tabletop, each of the four diaphragm blade units configured to form an exposure field on the X-ray detector;a beam-limiting drive unit configured to drive each of the four diaphragm blade units individually;a center transfer control unit configured to indicate a moving destination at a center of the exposure field;a beam-limiting control unit configured to receive information about a moving amount and a moving direction when the center of the exposure field moves, to control the beam-limiting drive unit to move each of the four diaphragm blade units individually, and to form the exposure field of the moving center that is concentric therewith; andan operating information processing unit configured to calculate the moving amount and the moving direction of the center of the exposure field when receiving an indication from the center transfer operation unit and to output the calculated moving amount and moving direction of the center of the exposure field to the beam-limiting control unit. 2. The apparatus according to claim 1, further comprising:a display control unit configured to display the exposure field on the display and the center position of the exposure field of the X-ray detector is made to correspond to a standard position in the display. 3. The apparatus according to claim 1, further comprising:a display control unit configured to display the exposure field on the display and the center position of the exposure field of the X-ray detector is made to correspond to a predetermined standard position in the display. 4. The apparatus according to claim 1, wherein each of the four diaphragm blade units narrows a detection range where X-rays of the X-ray detector are detected from the longer direction and the shorter direction of the tabletop, respectively, and forms the exposure field on the X-ray detector. 5. An X-ray diagnostic apparatus, comprising:a tabletop configured to support a subject;an X-ray tube configured to irradiate X-rays and disposed on one side of the tabletop;an X-ray detector configured to detect X-rays that penetrate the subject and disposed on the other side of the tabletop;four diaphragm blade units located between the X-ray tube and the tabletop, a first pair of diaphragm blade units configured to move antithetically in a longer direction of the tabletop, and a second pair of diaphragm blade units configured to move antithetically in a shorter direction of the tabletop, each of the four diaphragm blade units configured to form an exposure field on the X-ray detector;a beam-limiting drive unit configured to drive each of the four diaphragm blade units individually;an imaging system drive unit configured to drive the tabletop, the X-ray tube, and the X-ray detector, respectively, so that a detection range of X-ray detector is relative to movement in the longer direction and the shorter direction of the tabletop;an aperture information holding unit configured to hold aperture information about the longer direction of the tabletop and aperture information about the shorter direction of the tabletop;a center transfer operation unit configured to indicate the moving direction of a center of the exposure field; anda judgment unit configured to judge whether part or all of the exposure field exceeds the detection range of the X-ray detector or part or all of the exposure field enters an operation switching area formed at an edge of the detection range based on a moving amount and a moving direction information about the center of the exposure field and the aperture information held in the aperture information holding unit. 6. The apparatus according to claim 5, further comprising:an imaging system control unit configured to control the imaging system drive unit, to move the tabletop, the X-ray tube, and the X-ray detector, and to form an exposure field that is centered on a position of a moving destination when the judgment unit judges that part or all of the exposure field exceeds the detection range; anda beam-limiting control unit configured to control the beam-limiting drive unit to move the each of the four diaphragm blade units individually, and to form the exposure field that is centered on the position of the moving destination when the judgment unit judges that all of exposure field enters the detection range. 7. The apparatus according to claim 5, wherein the beam-limiting controls the imaging system drive unit to move the each of the four diaphragm blade units individually until the exposure field exceed the detection range of the X-ray detector, and the imaging system control unit controls the imaging system drive unit to move the tabletop, the X-ray tube, and the X-ray detector from the exposure field exceed the detection range of the X-ray detector. 8. The apparatus according to claim 5, wherein,the beam-limiting control unit controls the beam-limiting drive unit to move the each of the four diaphragm blade units individually until part or all of the exposure field enters the operation switching area and the imaging system control unit controls the imaging system drive unit to begin moving of the tabletop, the X-ray tube and the X-ray detector, andthe beam-limiting control unit controls the beam-limiting drive unit to decelerate the speed at which each the of the four diaphragm blade units is individually moved from part of the exposure field that enters the operation switching area and to form the exposure field that is centered on a position of a moving destination. 9. The apparatus according to claim 5, further comprising:a display control unit configured to display the exposure field on the display and the center position of the exposure field of the X-ray detector is made to correspond to a standard position in the display. 10. The apparatus according to claim 5, wherein the four diaphragm blade units narrow the detection range where X-rays of the X-ray detector are detected from the longer direction and the shorter direction of the tabletop, respectively, and forms the exposure field on the X-ray detector.