Collimator control method and apparatus, and X-ray CT apparatus

The present invention relates to a collimator control method and apparatus and an X-ray CT (computed tomography) apparatus, and more particularly to a method and apparatus for controlling a collimator for defining an impingement position of an X-ray beam on an X-ray detector, and an X-ray CT apparatus comprising such a collimator control apparatus. In order to control a collimator so that an X-ray impingement position on an X-ray detector is kept constant, an error of the impingement position of a fan-shaped beam () in the direction of side-by-side arrangement of a plurality of detector element rows in a detector element array () is detected (), and the collimator is controlled () based on the detected error so that the impingement position of the fan-shaped beam is kept at a constant position.