Simulations of Flow Diverters for Cerebral Aneurysms

Aneurysm refers to irreversible dilation of the artery, which, if left untreated, can be fatal. Although aneurysms can occur in any artery in the human cardiovascular system, most of them are found in the cerebral arteries, the thoracic and abdominal aorta. Once identified, they are typically treated through minimally invasive endovascular aneurysm repair (EVAR) surgeries, where a stent-graft is deployed at the aneurysm site using a catheter. Once deployed, this stent-graft relieves the weakened arterial wall from the hemodynamic loads and thus prevents the future of the aneurysmal artery. Some of the most common post-surgical complications associated with EVAR are stent-graft related, including thrombosis due to non-physiologic flow conditions, device migration, endoleaks and, in extreme cases, complete device failure. Computational fluid dynamics (CFD) and fluid-structure interaction (FSI) simulations offer a very lucrative pathway to quantitatively assess during the surgical planning phase if such complications can arise for a given patient or not, as elaborated below.

Simulations of Flow Diverters for Cerebral Aneurysms

Aneurysms found within the cerebral arteries or arteries of the brain are known as cerebral aneurysms. Unlike thoracic and abdominal aortic aneurysms, cerebral aneurysms are traditionally treated using flow diverters. Flow diverters are specialized braided structures that are designed to create favorable flow conditions within the aneurysm sac to promote thrombosis. The idea here is that once the aneurysm sac is fully thrombosed, the risk of aneurysm rupture will be low as the blood can no longer enter the aneurysm. As mentioned earlier, with the framework of FSI simulations, Navier-Stokes equations can be coupled with advection-diffusion equations to model the thrombosis process. In this manner, it is possible to model, on a patient-specific basis which flow diverter can lead to the complete occlusion of the cerebral aneurysm by rapid formation of thrombus.

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