Patent ID: 8094775

Claim:
An X-ray computer tomography apparatus comprising: an X-ray tube which generates X-rays; a two dimensional array type X-ray detector which detects the X-rays; a rotating mechanism which rotates the X-ray tube and the X-ray detector around a rotation axis; a pair of collimators which form X-rays from the X-ray tube into a cone beam shape; a collimator moving mechanism which separately moves the pair of collimators in a direction substantially parallel to the rotation axis; a reconstruction processing unit which reconstructs image data in a reconstruction range set by an operator based on an output from the X-ray detector; and a collimator control unit which controls a position of each of the collimators, wherein the collimator control unit controls the position of each of the pair of collimators in accordance with a distance between a central plane of the X-rays which corresponds to a cone angle of substantially 0° and an end face of the reconstruction range, and the collimator moving mechanism moves each of the pair of collimators in a range from an outermost position corresponding to a maximum cone angle corresponding to a width of the X-ray detector, beyond the central plane of the X-rays, at each edge of the reconstruction range, to an innermost position offset from a position corresponding to a cone angle of substantially 0° to an opposite side.