Papers by Keyword: Cerebral aneurysm

Abstract: Threshold image intensity for patient vascular models is determined instinctively. In this study, we used the simple method of threshold resolve to evaluate the effect of threshold image intensity level on computational fluid dynamics (CFD) of patient-specific cerebral aneurysm. This investigation involved five patients with internal carotid aneurysms collected in retrospect between August 2010 and October 2012. In 3-dimensional rotational angiography with digital subtraction angiography (DSA) image data, we set five straight line probe across the parent of the internal carotid artery and deliberate the average profile curve of the image intensity along this line. To determine the threshold image intensity level objectively, we calculated the threshold coefficient C_thre using this profile curve. The effect of C_thre value on vascular model configuration and the wall shear stress (WSS) distribution of the aneurysm was evaluated. Result shows for the inlet area and volume of the vascular model decreased and WSS increased according to the C_thre value increase. In one stage, the pattern of WSS distribution changed strangely and the threshold image intensity level can result reflective effects on CFD. This finding necessary to advance a further understanding of problems in image segmentation and solving the patient-specific aneurysm problems.

Abstract: The purpose of this study is to present a comparative study between Newtonian and non-Newtonian blood viscosity models for simulating the hemodynamic wall shear stress (WSS) of cerebral aneurysms. The non-Newtonian blood viscosity was modeled using the Carreau-Yasuda nonlinear model. Two realistic cerebral aneurysm models, derived from 3D angiography imaging, were studied and simulated via computational fluid dynamics solver based on finite volume method, with a pulsating sinusoidal waveform boundary conditions. The maximum wall shear stresses were found at the aneurysm’s neck and apex, the inlet arteriole recorded an average wall shear stress and as for the blebs and tips the wall shear stress values were remarkably low. The comparison indicated that non-Newtonian blood viscosity model predicted a lower range of WSS than of the Newtonian model, which provides more accuracy for simulating aneurysm hemodynamics.

Abstract: The purpose of this study is to accumulate data to predict the ruptures of aneurysms on the bifurcation of the middle cerebral arteries at the base of the brain. Particular stress is laid on understanding the elemental nature of branch flows with/without an aneurysm. Therefore, “flow patterns” and “wall shear stress”, which are important factors for the causes of ruptures, are investigated by the three-dimensional experiments in vitro and the two-dimensional numerical simulations with simplified models. In the branch arteries without an aneurysm, there is a possibility of growing aneurysms at the location slightly away from a stagnation point. If an aneurysm forms into a centrosymmetric shape for the inlet axis, it is considered that they tend to grow further in a symmetrical plane. From the viewpoint of the risk of ruptures, recirculation flows become problematic with the lower Reynolds number, while the influence of wall shear stress becomes larger with the higher Reynolds number.