1. A method for registering a set of dual energy images comprising first and second images, comprising: generating first and second Gaussian pyramids for said first and second images, respectively, each of said first and second Gaussian pyramids comprising a plurality of pyramid images, each corresponding to one of a plurality of pyramid levels; initializing an optical flow value for a first pyramid level; sequentially updating the optical flow value for each pyramid level based on the corresponding pyramid images of the first and second Gaussian pyramids based on an optimization function comprising a similarity measure and a regularizer; and registering said first and second images based on a final optical flow value.