Subject-Specific Modeling of Intracranial Aneurysms Juan R. Cebral* a , Monica Henandez b , Alejandro Frangi b , Christopher Putman c , Richard Pergolesi c , James Burgess c a School of Computational Sciences, George Mason University, Fairfax, VA 22030 b Aragon Institute of Engineering Research, University of Zaragoza, 50015 Zaragoza, Spain c Inova Fairfax Hospital, Falls Church, VA 22042 ABSTRACT Characterization of the blood flow patterns in cerebral aneurysms is important to explore possible correlations between the hemodynamics conditions and the morphology, location, type and risk of rupture of intracranial aneurysms. For this purpose, realistic patient-specific models are constructed from computed tomography angiography and 3D rotational angiography image data. Visualizations of the distribution of hemodynamics forces on the aneurysm walls as well as the intra-aneurysmal flow patterns are presented for a number of cerebral aneurysms of different sizes, types and locations. The numerical models indicate that there are different classes of intra-aneurysmal flow patterns, that may carry different risks of rupture. Keywords: cerebral aneurysm, hemodynamics, computational fluid dynamics, CT angiography, 3D rotational angiography 1. INTRODUCTION Intracranial aneurysms are pathological dilatations of cerebral arteries. They tend to occur at or near arterial bifurcations, mostly in the circle of Willis [1]. They can be roughly classified into terminal, lateral or bifurcation aneurysms depending on their relation to the parent vessel. The most serious complication happens when the aneurysm breaks, since this has fatal consequences in 2.6 - 9.8% of the patients and serious consequences in 10.9% of the patients due to intra cranial bruise, subsequent recurrent bleeding, hydrocephaly and spasms in brain vessels [2,3,4]. The reasons for genesis, growth and rupture of saccular aneurysms are not clear. However, hemodynamic factors, such as wall shear stress, pressure, residence time and flow impingent, are thought to play a role in the pathogenesis of aneurysms and thrombosis [5]. Since measuring hemodynamic quantities in vivo is difficult, various modeling approaches have been considered in the past [6]. In vitro studies allow very detailed measurement of hemodynamic variables, but cannot be used in a straight manner for clinical evaluation of individual cases. In vivo image-based computational models have only since recently been attempted with promising results [7, 8]. In this paper, a methodology for realistic patient-specific modeling of the hemodynamics in cerebral aneurysms is described. Using this methodology, the flow dynamics in several models constructed from computed tomography angiography and 3D rotational angiography images are analyzed. 2. METHODS Subject-specific models of cerebral aneurysms are constructed from 3D anatomical image data obtained with computed tomography angiography (CTA) and 3D rotational angiography (3DRA). Each of these imaging modalities has some advantages and disadvantages. For instance CTA images contain bright bone structures that in some cases are difficult to separate from the vasculature. In 3DRA images this problem is greatly reduced by the use of intra-arterial contrast. However, aneurysms located in the anterior communicating artery require special attention