Portal Vein Registration for the Follow-Up of Hepatic Tumours Arnaud Charnoz, Vincent Agnus, and Luc Soler IRCAD, 1, place de l’Hˆopital - F67091 Strasbourg Cedex - France Arnaud.Charnoz@ircad.u-strasbg.fr Abstract. In this paper, we propose an original method which permits a follow-up of intra-patient evolution of tumours in the liver by using a registration of the portal vascular system. First, several methods to segment the liver data structures (liver, vascu- lar systems and tumours) on computed tomography scans are presented. Secondly, the skeleton of the vessels is computed and transformed into a graph representation. Then, the intra-patient graph registration is com- puted to determine an approximation of liver deformation. Finally, the deformation permits to match tumours to diagnose their evolution. For each step, we present the methods we used and their results on CT- scan images. 1 Motivations Liver surgery is a field in which computer-based surgery planning has great impact on selection of therapeutic strategy. In this paper, we focus on the follow- up of tumours from the same patient between two acquisitions. We propose an automatic method which permits to show how tumours evolve. The main purpose is to match tumours between two different moments. Tumour matching provides an automatic framework to diagnose their evolu- tions. The comparison amongst matched tumours permits to see their evolutions by comparing their volumes. A tumour cannot be matched if it appeared or dis- appeared between the two acquisitions. Tumour matching can not be accurately performed by using only their lo- calization information. Indeed, between two acquisitions, their localization and shape can vary a lot. The shape deformation is due to disease development and the localization changes are due the deformation of liver. The liver deformation gives an estimate of tumour displacement that helps to track them. The liver is lacking of reference points allow the estimation of its deformation, so its inner vascular system is preferred, particularly the portal system. On the CT-scan images, hepatic vessels are enhanced with a contrast medium. The vascular system gives a better reference point set in two respects: a) topologically, by providing junction points as reference points, b) geometrically, with diameter and orientation information of incident branches. C. Barillot, D.R. Haynor, and P. Hellier (Eds.): MICCAI 2004, LNCS 3216, pp. 878–886, 2004. c  Springer-Verlag Berlin Heidelberg 2004