An apparatus for improving the tomographic image quality by preventing the
tomographic image contrast from degrading and preventing artifact from
occurring even if many scattered radiations occur. An X-ray detection
array obtains first detection data using the X-ray detection elements
corresponding to an area not shielded by a collimator. Further, the X-ray
detection array obtains second detection data using the X-ray detection
elements corresponding to an area shielded by the collimator. A central
processing unit corrects the first detection data based on the detection
data including the first and second detection data. Finally, the central
processing unit generates a tomographic image for an imaging area of the
imaging object.