Investigation of characteristic hemodynamic parameters indicating thinning and thickening sites of cerebral aneurysms

Cellular and animal experiments and computational fluid dynamics (CFD) have revealed that mechanisms of the initiation, growth and rupture of a cerebral aneurysm are related to hemodynamics. By direct observation of a cerebral aneurysm during craniotomy, thinning or thickening sites can be found on the aneurysmal wall. The thinning site of a cerebral aneurysm is considered to be at high risk of rupture. In addition, the thickening site of a cerebral aneurysm is not necessarily in a stable state since arteriosclerosis may have occurred. Hence, information on wall conditions, i.e., thinning and thickening, of a cerebral aneurysm is beneficial for clinical diagnosis and treatment. In this study, a hemodynamic parameter to effectively estimate the thinness or thickness of cerebral aneurysmal walls was investigated. CFD of hemodynamics in cerebral aneurysms developed at the anterior communicating artery (ACoA), a common site of cerebral aneurysms, was performed, and characteristic distributions of hemodynamic parameters were investigated by comparing the computational results with clinical images. As a result, a high value of the time-averaged wall shear stress (TAWSS) was found to be present at thinning sites, while a low TAWSS and a high relative residence time (RRT) of an indicator of blood retention were observed at thickening sites. Thinning and thickening sites each have their own characteristics distribution of hemodynamic parameters.