1. A method of enhancing an image of an object so as to increase the visibility in the image of at least one skeletal structure within the object, wherein the image is characterized by a plurality of pixels, each pixel having an associated pixel value that represents the image intensity of a corresponding unit volume of the object, the method comprising: generating a two-dimensional (2D) reconstructed image from a three-dimensional (3D) scan of the object, wherein the 2D reconstructed image includes the skeletal structure; generating a 2D x-ray image of the object, wherein the 20×-ray image includes the skeletal structure; for each of the 2D reconstructed image and the 2D x-ray image a) selecting at least a first neighborhood and a second neighborhood within the image, b) constructing an operator configured to select, within the first and second neighborhoods, one or more pixels having an optimal pixel value, and to eliminate the remaining pixels in the neighborhoods; c) applying the operator to the selected neighborhoods so that only the pixels having the optimal pixel values remain in the selected neighborhoods, and the remaining pixels in the selected neighborhoods are eliminated to produce an enhanced image; and registering the enhanced 2D x-ray image with the enhanced 2D reconstructed image by deriving a transformation between a coordinate system of the enhanced 2D xray image and a different coordinate system of the enhanced 2D reconstructed image.