In vitro hydrodynamical study on aneurysmal morphology for treating intracranial aneurysms using particle imaging velocimetry

Low-porosity stents such as flow diverters and the flow isolator, which we developed in a previous study, are expected to provide an effective and minimally invasive treatment for intracranial aneurysms (IAs). After inserting a stent, thrombus formation is promoted by the stagnation of IA blood flow. Consequently, IA embolization can occur. Therefore, IA flow intensity significantly affects IA emboli zation treatment. IA morphology such as aneurysm size, aspect ratio, and bottleneck factor are important parameters as general indices of IA rupture. Meanwhile, existing litera-ture suggests that IA morphology is considerably affected by IA flow and IA embolization. Hence, this work investi gates the relationship between IA flow intensity and IA morphology by using particle imaging velocimetry (PIV) and in vitro flow simulation with IA and parent vessel models. The PIV results showed that the area mean shear rate (AMSR), a hemodynamical index of thrombus formation, was higher in IA models with higher neck widths, lower aneurysm heights, and smaller dome sizes. This implies that thrombus formation is inhibited in a wide-neck and small aneurysm. Moreover, stents with effective flow-reduction properties are required for a reliable IA embolization treat -ment. The AMSR was well expressed by a power function using the Reynolds number and IA morphology as parameters.