1. A method for multimodal image registration, the method comprising the steps of: providing a pair of images, each image of said pair acquired from a different imaging modality, each said image comprising a plurality of intensities corresponding to a domain of points on an N-dimensional grid; defining an intensity correction function that corrects the intensities of a first of said pair of images in terms of the intensities of the second of said pair of images; defining a registration transformation function that registers said second image with said first image, wherein said intensity correction function and transformation function are functions of a plurality of parameters; obtaining corrections to said plurality of parameters by minimizing an energy functional of a square difference of said intensity corrected first image and said registration transformed second image; and updating said intensity correction function and said registration transformation function based on said corrected plurality of parameters.