Towards Regional Elastography of Intracranial Aneurysms Simone Balocco 1,2 , Oscar Camara 1,2 , Alejandro F. Frangi 1,2 1 Center for Computational Imaging & Simulation Technologies in Biomedicine, Universitat Pompeu Fabra, Barcelona, Spain. 2 Networking Center on Biomedical Research (CIBER-BBN), Barcelona, Spain Abstract. Weak spots in the aneurysm could be identified estimating the re- gional stiffness of the wall. Our approach consists in defining a parametric biomechanical model of the vessel which, given the patient’s vascular mor- phology and the blood in- and outflow obtained from non-invasive imaging as well as parameters describing the local elasticity of the wall, enables the com- putation of the theoretical deformed wall position. The distance between this latter and the one obtained from the aneurysm pulsation is iteratively minimized in order to estimate the optimal set of stiffness parameters. In order to reduce the number of variables to estimate, the aneurysm morphology is clustered into a limited number of regions with uniform stiffness. A random noise perturba- tion (<5mm) is applied to the reference deformations and strains, showing that the robustness of the clustering decreases to 75% and errors of the stiffness es- timates remain below 10% of the reference values. 1 Introduction A cerebral aneurysm is a vascular disease in which the weakness of the cerebral artery wall causes a localized dilation of the blood vessel and occasionally its rupture thus leading to stroke. The assessment of the aneurysm elasticity may allow the iden- tification of potential rupture sites such as blebs [1] before a noticeable modification of the aneurysm shape and the periodical survey of structural changes of the wall pre- dict disease progression. Although non-invasive estimation of tissue elasticity in vivo in other vascular segments has been demonstrated [2], these techniques have limited applicability in intracranial segments due to limited imaging resolution [1] since aneu- rysmal wall motion would require high spatio-temporal accuracy in 3D to be detected. The elastic properties of vessels can be deduced indirectly using an inverse prob- lem formulation. In our application, the inverse problem framework will consist in estimating the mechanical parameters of a biomechanical model of the aneurysm based on non-invasive measurements of the dynamic pulsation and blood flow. The first theoretical framework addressed to the elasticity estimation of cerebral aneu- rysms has recently been proposed by Kroon and Holzapfel [3]. The authors present a numerical model characterized by a spherical shape discretized into a small number of mesh elements and by boundary conditions based on a uniform distribution of the pressure along the surface. The feasibility of their approach was shown on synthetic data. In this work, we present a more realistic approach for the estimation of regional aneurysmal stiffness where, for the first time, patient-specific morphology and inflow