Normalized similarity measures for medical image registration

Two new similarity measures for rigid image registration, based on the normalization of Jensen’s difference applied to Rényi and Tsallis-Havrda-Charvát entropies, are introduced. One measure is normalized by the first term of Jensen’s difference, which in our proposal coincides with the marginal entropy, and the other by the joint entropy. These measures can be seen as an extension of two measures successfully applied in medical image registration: the mutual information and the normalized mutual information. Experiments with various registration modalities show that the new similarity measures are more robust than the normalized mutual information for some modalities and a determined range of the entropy parameter. Also, a certain improvement on accuracy can be obtained for a different range of this parameter.