1. An image processing apparatus comprising: an image mapping unit for generating a mapping image in which first radiation images of multi-energy bands with respect to a local region of a body are mapped to a second radiation image with respect to a thickness variable phantom; an image analyzing unit for analyzing a reference region corresponding to normal tissue in the local region and a peculiar region corresponding to abnormal tissue in the local region based on the mapping image; and an enhancement image generating unit for generating a tissue enhancement image that has a shape of the local region in the first radiation images and enhances regions of pixel positions, that are mapped to the peculiar region, of the first radiation images.