Mutual Information-based Image Registration: Mutual Information-based Image Registration of Digitally Reconstructed Radiographs and Electronic Portal Images

Mutual information, in addition to having application in fields such as communication and computer vision, has resulted in fully automated image registration methods. Mutual information, in the context of image registration, is given by the difference between the sum of the entropies of individual overlapping images and the joint entropy of the combined images. It is a measure of the reduction in uncertainty about one image due to knowledge of the other. The book begins with a broad overview of medical image registration as the context in which to present the discrete mutual information-based registration method. The theory and mathematics of discrete mutual information and its origin in information theory is presented, followed by discussion of its application in image registration. Finally, a specific example of mutual information-based medical 2D-2D image registration is presented: registration of digitally reconstructed radiographs (DRRs) and electronic portal images (EPIs).