A fast and accurate method to register medical images using wavelet Modulus Maxima

This paper presents a fast, accurate and automatic method to register image s of rigid bodies. It uses wavelets to obtain control points. Wavelets are not shift invariant but the structures determined by the wavelet high pass image, the Modulus Maxima Image, provide the information necessary for a fa st-rough convergence. These structures represent shapes from which we segme nt the invariant shapes for the images being registered, For example, the M RI and CT images of the brain can be considered as rigid bodies that do not undergo a change in shape over reasonable periods of time. By using a conv ex hull, we make the procedure insensitive to the internal changes in the o bject. Hence, even with the growth of tumors, the procedure registers brain images very accurately. The method uses the correlation coefficient to mea sure the similarity between images and to determine how well the images are registered. The method has been extensively tested with various types of i mages and in all cases the registration accuracy is very high. The correlat ion coefficient used to validate the registrations has deficiencies that oc casionally required a visual inspection to terminate the algorithm after a point of marginal improvement. (C) 2000 Elsevier Science B.V. All rights re served.