Patent ID: 7016465

Claim:
An X-ray CT apparatus comprising: an X-ray source for irradiating an X-ray on a subject; an X-ray detector arranged to be opposite to the X-ray source for obtaining an X-ray transmission data of the subject; a rotary stage holding the subject thereon and rotating around its rotation axis orthogonal to an optical axis of the X-ray, the rotary stage being disposed between the X-ray source and the X-ray detector; an image reconstruction calculation unit for obtaining a tomogram of the subject along a plane orthogonal to the rotation axis by using the X-ray transmission data of the subject obtained at each rotation of a predetermined angle of the rotary stage while rotating the rotary stage; an optical camera for photographing the subject placed on the rotary stage from a position on the rotation axis of the rotary stage or a position in vicinity of the rotation axis; a CT imaging region calculation unit for calculating a region where CT imaging is possible around the rotation axis based on information relating to a positional relation of the X-ray source, the X-ray detector and the rotary stage in a direction of the optical axis of the X-ray and information relating to a size of a light receiving surface of the X-ray detector; and a displaying unit for displaying the region calculated by the CT imaging region calculation unit being superimposed with an optical image of the subject photographed by the optical camera.