To accurately discriminate normal and abnormal shadows, to improve the detection rate, and to reduce the number of pseudo-positive reactions as much as possible.

The subject device is for discriminating the normal and abnormal shadows using texture information on a tomogram. The normal and abnormal shadows are discriminated based on the texture information on both an original image and an interpolated image as one method for discriminating the normal and the abnormal. In addition, the normal and the abnormal shadows may be discriminated based on the texture information on the density between the original image and the interpolated image or based on the similarity of the shape of shadows between the original image and the interpolated image.