Patent Number: 
Section: claims

1. A tomography apparatus comprising:a filter configured to adjust distribution of a radiation dose;a radiation detection unit configured to detect a radiation dose transmitted through the filter and through an object,wherein the filter comprises:a plate filter including plate-shaped materials; anda slope filter having two materials each having a slope surface, and disposed, at a predetermined interval, symmetrically with respect to a straight line connecting a focal point of a radiation source and the radiation detection unit, andwherein the shape of the filter is obtained by combining the plate filter and the slope filter. 2. A tomography apparatus according to claim 1, further comprising:an acquisition unit configured to acquire information about the object; anda control unit configured to control the distribution of the transmitted radiation dose according to the information about the object acquired by the acquisition unit. 3. The tomography apparatus according to claim 2, wherein the control unit controls the distribution of the transmitted radiation dose by selecting one filter from a plurality of filters. 4. The tomography apparatus according to claim 2, further comprising:a holder configured to hold the object,wherein,the acquisition unit acquires information about the holder andthe control unit controls the distribution of the transmitted radiation dose according to the information about the holder acquired by the acquisition unit. 5. The tomography apparatus according to claim 4, wherein the control unit controls the distribution of the transmitted radiation dose by determining a combination of a plurality of materials absorbing radiation according to the information about the holder and changing the shape of the filter. 6. The tomography apparatus according to claim 4, wherein the holder holds a breast as the object in a predetermined shape,the acquisition unit acquires information about a shape of the holder, andthe control unit controls the distribution of the transmitted radiation dose according to the information about the shape of the holder. 7. The tomography apparatus according to claim 6, wherein, the holder comprises:an insertion hole configured to receive the breast;an insertion unit configured to cover the breast; anda suction unit connected to the holder, the suction unit configured to suck air in the insertion unit to hold the breast on an inner peripheral surface of the insertion unit. 8. The tomography apparatus according to claim 7, further comprising:a rotation unit configured to rotationally move the radiation source, the filter, and the radiation detection unit along an outer periphery of the holder; anda fixing unit configured to fix the holder,wherein the fixing unit fixes the holder to align an axis perpendicular to a center point of a plane having the insertion hole of the holder with a rotation axis of the rotational movement. 9. The tomography apparatus according to claim 7, wherein the breast sucked by the suction unit has a circular cross-sectional shape. 10. The tomography apparatus according to claim 2, wherein the control unit controls a thickness of the plate filter by combining a plurality of the plate-shaped materials according to the information about the holder. 11. The tomography apparatus according to claim 2, wherein the control unit controls the predetermined interval according to the information about the holder. 12. The tomography apparatus according to claim 2, wherein the slope filter, according to the information about the holder, absorbs radiation and forms the slope surface having a predetermined angle by combining the plurality of materials each having a slope surface. 13. The tomography apparatus according to claim 2, wherein the control unit controls the distribution of the transmitted radiation dose to a uniform distribution of radiation detected by the radiation detection unit.