1. A method for registering a plurality of images, comprising the steps of: determining a spatial gradient magnitude for each pixel in each image to determine a corresponding energy image; transforming each energy image according to motion parameters associated with the energy image; maximizing an average sum of the transformed energy images; updating the motion parameters according to the maximized average sum; repeating the transforming, maximizing and updating steps until a predetermined termination condition is reached; and registering the plurality images with each other according to the updated motion parameters.