Résumé
Between 2 and 6 % of the population harbour at least one intracranial aneurysm and around 0.5% ofthem are expected to rupture. Given the human and economic cost associated with cerebral vasculardiseases, a systematic medical screening of intracranial aneurysms would be worth organizing. However,the per-procedural risk being about 1%, no such screening is organized because a reliable assessment ofthe aneurysms vulnerability is still lacking. Nevertheless, with brain imaging being more frequently andwidely used, a growing number of intracranial aneurysms are being diagnosed, raising the problem ofwhich aneurysms harbour a sufficiently high risk of rupture to merit a prophylactic repair. This questionis still unsolved at the moment and therapeutic decision for unruptured aneurysms still a challenge.We develop, in this study, a way assessing the risk of rupture of an aneurysm. The method stems fromtwo recent results obtained within the IRRAs consortium (http://irras.net/) and supported by existingdata in the literature. First, by characterizing the mechanical properties of human aneurysms tissues andclassifying them with respect to the available epidemiological/histologic/medical data, Costalat et al.2011 demonstrated that the medical status of an aneurysm (undegraded, degraded, close to rupture orruptured) is strongly correlated with the aneurysmal tissue property (stiff, intermediate, soft). Second,as a follow up of the experimental study of Costalat et al. 2011, Sanchez et al. 2013 performed anumerical study of the blood flow in cerebral aneurysms under realistic in vivo conditions. The Fluid-Structure Interaction (FSI) computations showed a significant difference between the systo-diastolicaneurysmal volume variations corresponding to the soft (close to rupture or ruptured) and the stiff(undegraded) tissue. These results are not only robust with respect to the many uncertainties related toany biomechanical simulation performed under in vivo conditions, but they are also consistent with aclinical study by Hayakawa et al. 2005 who came to the conclusion that the detection of pulsation in anunruptured aneurysm is a clue of an important risk of rupture of the aneurysm. However, the differenceobserved in the simulations between stiff and soft tissues are large enough to be detected by advancedMagnetic Resonance Imaging protocols able to measure displacements as small as 0.04 mm (Karmoniket al., 2010).The presented method couples soft tissues measurements, advanced medical imaging and FSIcomputations in order to build a quantitative index of risk of rupture of cerebral aneurysms.