Subarachnoid hemorrhage is a life threatening condition, caused by rupture of an intracranial aneurysm. Unruptured aneurysms are often found incidentally, making prophylactic treatment an option. Currently, risk-assessment of unruptured aneurysms is not s pecific enough for decision making in many patients, and does not include evaluation of shape. Biomechanically, the aneurysm ruptures when wall tension exceeds the strength of the wall tissue. Both wall tension and other hemodynamic factors are greatly in fluenced by vascular geometry, but studies are difficult because of complex anatomy, making simplified physics inaccurate. Computer assisted simulation have recently been applied on studies of hemodynamics, and we recently published two studies reporting simulation results supporting clinical knowledge.The primary objective of the project is to investigate whether fluid dynamics simulations based on patient-specific imaging can be used to quantify risk for development and rupture of intracranial aneurys ms. This involves development and utilization of novel numerical algorithms for simulations of fluid-structure interaction in cerebral vessels and aneurysms. The simulation results will be compared with clinical data to evaluate the predictive ability of the method. We aim to develop custom software suits that are efficient and reliable enough to be used on desktop computers. The project will also generate better knowledge of cerebrovascular hemodynamic patophysiology and new tools for further research in this area.The project is an inter-disciplinary collaboration between neurosurgeons at the University hospital of North Norway, scientists in applied mathematics and scientific computing at the Centre of Excellence ?Center for Biomedical Computing?, S imula Research Laboratory and SINTEF ICT, Trondheim. Furthermore, we have established collaboration with internationally leading experts in fluid-structure interaction in Texas and imaging technology in Italy.