title: Experimental insights into flow impingement in cerebral aneurysm by stereoscopic particle image velocimetry: transition from a laminar regime.
abstract: This study experimentally investigated the instability of flow impingement in a cerebral aneurysm, which was speculated to promote the degradation of aneurysmal wall. A patient-specific, full-scale and elastic-wall replica of cerebral artery was fabricated from transparent silicone rubber. The geometry of the aneurysm corresponded to that found at 9 days before rupture. The flow in a replica was analysed by quantitative flow visualization (stereoscopic particle image velocimetry) in a three-dimensional, high-resolution and time-resolved manner. The mid-systolic and late-diastolic flows with a Reynolds number of 450 and 230 were compared. The temporal and spatial variations of near-wall velocity at flow impingement delineated its inherent instability at a low Reynolds number. Wall shear stress (WSS) at that site exhibited a combination of temporal fluctuation and spatial divergence. The frequency range of fluctuation was found to exceed significantly that of the heart rate. The high-frequency-fluctuating WSS appeared only during mid-systole and disappeared during late diastole. These results suggested that the flow impingement induced a transition from a laminar regime. This study demonstrated that the hydrodynamic instability of shear layer could not be neglected even at a low Reynolds number. No assumption was found to justify treating the aneurysmal haemodynamics as a fully viscous laminar flow.
authors: Center for Advanced Biomedical Sciences, Waseda University, Tokyo, Japan. takanobu_yagi@aoni.waseda.jp
authors: Takanobu
authors: T
authors: Yagi
authors: Ayaka
authors: A
authors: Sato
authors: Manabu
authors: M
authors: Shinke
authors: Sara
authors: S
authors: Takahashi
authors: Yasutaka
authors: Y
authors: Tobe
authors: Hiroyuki
authors: H
authors: Takao
authors: Yuichi
authors: Y
authors: Murayama
authors: Mitsuo
authors: M
authors: Umezu
mesh_terms: D001783:Blood Flow Velocity; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000473:pathology / Q000503:physiopathology*; D008875:Middle Aged; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D012212:Rheology