Patent ID: 8094774

Claim:
An X ray computed tomography apparatus comprising: an X ray tube configured to generate X rays; an X ray detector configured to detect X rays generated from the X ray tube and transmitted through a subject placed on a top; a support unit configured to rotatably support the X ray tube and the X ray detector; a bed configured to include the top so as to allow the top to move along a direction substantially parallel to a body axis of the subject; a control unit configured to control the X ray tube, the X ray detector, the support unit, and the bed to scan the subject with X rays while moving the top along the direction and changing a speed of the top; an acquisition unit configured to acquire projection data via the X ray detector; an extraction unit configured to extract projection data necessary for reconstruction of image data associated with a predetermined slice position from the acquired projection data; a weighting unit configured to apply a weighting function to the extracted projection data, the weighting function being determined in accordance with the speed of the top during the scan of the subject, the extracted projection data including first projection data and second projection data, the first projection data being acquired within a predetermined period including a predetermined time at which projection data is acquired at the predetermined slice position, the second projection data being acquired outside the predetermined period, the weighting function having a weight distribution which applies a smaller weight to the second projection data than to the first projection data; and a reconstruction unit configured to reconstruct the image data on the basis of the first projection data and the second projection data to which the weights are assigned.