A computed tomography apparatus, including: an X-ray helical scanning device including an X-ray generator and an X-ray detector arranged in a gantry, the helical scanning device configured to provide a continuous scan and to obtain projection data of a scanned object arranged on a platform; and control unit configured to control at least one of the X-ray helical scanning device and the platform so as to generate the continuous scan with a helical pitch that is based on a height of a detector row of the X-ray detector projected onto an iso-center of the gantry.