An image processing method for processing image data comprises the steps of obtaining scanpath data corresponding to original image data, determining regions of interest for the original image data based on the obtained scanpath data, and mapping tone values of the original image data corresponding to each region of interest in order to obtain tone-mapped image data. The heat dissipating device includes a heat sink and a fan generating airflow. The present invention is provided with a knee lifter mechanism which is disposed upon a right lower end of the bed, which is equipped with a knee operation lifter, and which has a knee lifter drive arm which rotates by a swing of the knee operation lifter, wherein the knee lifter drive arm is joined to the lifter operating plate. The bandpass filters filter the detected electrical signal.