Numerical Modeling of the Flow in Cerebral Aneurysms Can Predict Thrombus Deposition Regions Following Vascular Interventions

Giant intracranial aneurysms present a grave danger of hemorrhage, cerebral compression, and thromboembolism. Fusiform aneurysms present a particular challenge for interventional treatment since these lesions cannot be completely removed from the circulation by clipping or coiling without sacrificing flow to the distal vasculature. In some cases, these lesions can be treated by interventions eliminating pathological hemodynamics, such as indirect aneurysm occlusion or deployment of a flow diverter stent (FDS). The first approach consists of proximal occlusion, distal occlusion, or trapping, sometimes performed with a bypass supplying flow from collateral circulation. In the second approach, a flow diverter device is used to reconstruct the parent vessel geometry and redirect the flow away from the aneurysmal sac. This is achieved due to the denser struts of an FDS relative to a standard stent, which provide resistance to the flow across its walls. Both interventional approaches often result in thrombus deposition (TD) in the aneurysm sac that is considered protective. Despite their advantages, these treatments introduce complications related to thrombotic occlusion of vital perforators or branch arteries. A virtual model, that could predict TD regions that result from flow alteration could help evaluate various treatment options. In addition to biochemical factors, an important role in the TD process may be played by hemodynamics. Previous studies demonstrated that flow regions with elevated TD potential are characterized by low velocities and near-wall shear stresses as well as increased flow residence time [1, 2]. The current study extends this patient-specific CFD methodology to predict TD regions following vascular interventions, such as proximal vessel occlusion and FDS deployment.