MR-ultrasound imaging registration using 2D spatial phase images

This paper deals with multimodal magnetic resonance (MR) - ultrasound (US) image registration. One of the major difficulties in such a registration is the lack of correspondence between the gray levels of the pixels in the two modalities. To tackle it, several authors proposed the use of the mutual information as similarity measure in the registration process. Moreover, a few papers proposed recently the use of spatial phase images instead of native intensity images. Phase images have the advantage to contain structural information on the images, free of the energetic information. Although very interesting, to our knowledge only subjective results have been reported concerning the gain of accuracy using phase images. The goal of this paper is to propose a quantitative approach for evaluating the contribution of spatial phase images obtained with monogenic and 2D isotropic analytic signal in MR-US registration.