Mutual Information: A Similarity Measure for Intensity Based Image Registration

Mutual information (MI) was independently proposed in 1995 by two groups of researchers (Maes and Collignon of Catholic University of Leuven (Collignon et al. 1995) and Wells and Viola of MIT (Viola and Wells 1995)) as a similarity measure for intensity based registration of images acquired from different types of sensors. Since its introduction, MI has been used widely for a variety of applications involving image registration. These include medical imaging (Holden et al. 2000; Maes et al. 1997; Studhilme et al. 1997; Wells et al. 1996), remote sensing (Chen et al. 2003ab), and computer vision (Chen and Varshney 2001a). The MI registration criterion states that an image pair is geometrically registered when the mutual information between the two images reaches its maximum. The strength of MI as a similarity measure lies in the fact that no assumptions are made regarding the nature of the relation between the intensity values of the image, as long as such a relationship exists. Thus, the MI criterion is very general and has been used in many image registration problems in a range of applications.