Influence of wall elasticity in patient-specific hemodynamic simulations Ryo Torii a, * , Marie Oshima b , Toshio Kobayashi c , Kiyoshi Takagi d , Tayfun E. Tezduyar e a Department of Chemical Engineering, Imperial College, London SW7 2AZ, United Kingdom b Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan c Japan Automobile Research Institute, 2530 Karima Tsukuba-shi, Ibaraki 305-0822, Japan d Department of Neurosurgery, Ogura Hospital, 4-2-5 Nakamachi, Setagaya-ku, Tokyo 158-8585, Japan e Mechanical Engineering, Rice University—MS 321, 6100 Main Street, Houston, TX 77005, USA Received 25 February 2005; accepted 20 July 2005 Abstract Recent reports indicate that the rupture risk for cerebral aneurysms is less than the risk of surgical complications. Being able to predict the rupture of aneurysms would help making better-informed decisions and avoiding unnecessary surgical operations. The wall shear stress is known to play an important role in vascular diseases. We carry out computational fluid–structure interaction analyses to investigate the influence of the arterial-wall deformation on the hemodynamic factors, including the wall shear stress distribution. The results show various patterns of this influence, depending very much on the arterial geometry. Ó 2005 Elsevier Ltd. All rights reserved. 1. Introduction In the year 2000, nearly 15,000 people died in Japan because of subarachnoid hemorrhages [1]. It is also reported that 95% of the subarachnoid hemorrhages are caused by the rupture of cerebral aneurysms [2]. Although the rupture risk for aneurysms is reported to be under 0.1% if their diameters are less than 10 mm [3], most aneurysms can be operated on if they are detected. On the other hand, it is also reported in [3] that the risk of postoperative sequelae is over 10%. There- fore, it is important to identify the cases where the aneu- rysm is exposed to a high risk of rupture, and avoid unnecessary surgical operations in other cases. Deter- mining the risk factors for rupture is also important in preventing it from happening. Because of the recent developments in medical imaging technology, more aneurysms are detected in physical examinations. In par- ticular, it is reported that 6% of the population in Japan have cerebral aneurysm [4]. As the medical imaging diagnoses become more improved and popular, more aneurysms will be identified. While the risk estimation for the rupture of aneurysm mostly relies on the experi- ence of the neurosurgeons now, more objective ways of risk estimation would be very helpful. In predicting the rupture of aneurysms, the mecha- nisms of growth and rupture need to be investigated. Hemodynamic factors, such as the blood pressure and wall shear stress (WSS), have been deemed to be impor- tant factors in cerebral aneurysm [5]. Recently, it was also shown through physiological experiments [6] that hemodynamic forces play a role in other vascular dis- eases, such as atherosclerosis. In vivo measurements or experiments cannot estimate the WSS directly, and their spatial and temporal resolutions are currently not suffi- cient to investigate the transient behavior of the pulsatile 0045-7930/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.compfluid.2005.07.014 * Corresponding author. E-mail address: r.torii@imperial.ac.uk (R. Torii). Computers & Fluids xxx (2005) xxx–xxx www.elsevier.com/locate/compfluid ARTICLE IN PRESS