Image registration in medical imagery is one useful technique with an important role especially for pathology survey and control, medical treatment, or for post-operative control. It is based essentially on the similarity criterion measurement because it defines the objective criterion used to estimate registration quality between the homologous structures of images. This paper describes one application of the SSIM method as a similarity metric in the image registration technique. Usually the SSIM method is used in the images' quality measurement, it consists in the combination of the comparison of luminance, the comparison of contrast, and the comparison of structure between two images. This property allowed us to adapt this approach in MR image monomodal registration and demonstrate its performance.