Patient-specific flow analysis of brain aneurysms at a single location: Comparison of hemodynamic characteristics in small aneurysms

Division of Interventional Neuroradiology, David Geffen School of Medicine, University of California, 10833 LeConte Ave., Box 951721, Los Angeles, CA 90095, USA.
Medical & Biological Engineering (Impact Factor: 1.73). 10/2008; 46(11):1113-20. DOI: 10.1007/s11517-008-0400-5
Source: PubMed


The purpose of this study is to examine and compare the hemodynamic characteristics of small aneurysms at the same anatomical location. Six internal carotid artery-ophthalmic artery aneurysms smaller than 10 mm were selected. Image-based computational fluid dynamics (CFD) techniques were used to simulate aneurysm hemodynamics. Flow velocity and wall shear stress (WSS) were also quantitatively compared, both in absolute value and relative value using the parent artery as a baseline. We found that flow properties were similar in ruptured and unruptured small aneurysms. However, the WSS was lower at the aneurysm site in unruptured aneurysms and higher in ruptured aneurysms (P < 0.05). Hemodynamic analyses at a single location with similar size enabled us to directly compare the hemodynamics and clinical presentation of brain aneurysms. The results suggest that the WSS in an aneurysm sac can be an important hemodynamic parameter related to the mechanism of brain aneurysm growth and rupture.

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Available from: Aichi Chien, Dec 10, 2014
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    • "In aneurysms, areas of stasis can be observed in particular at sites close to the dome: the histological changes induced by local stagnation could lead to aneurysm growth and possibly subsequent rupture, since decreased wall shear stress is associated with inflammation and endothelial cell dysfunction. In addition, by using patient-based data to reconstruct aneurysms, computational fluid dynamic studies have exhibited considerable interindividual variability which is accompanied by different hemodynamic profiles [87] [88] [89] [90]. Therefore, it is challenging to discern the exact hemodynamic conditions inciting growth and predisposing these lesions to rupture. "
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    ABSTRACT: Atherosclerosis is the main cause of morbidity and mortality in the Western world. Inflammation and blood flow alterations are new markers emerging as possible determinants for the development of atherosclerotic lesions. In particular, blood flow exerts a shear stress on vessel walls that alters cell physiology. Shear stress arises from the friction between two virtual layers of a fluid and is induced by the difference in motion and viscosity between these layers. Regions of the arterial tree with uniform geometry are exposed to a unidirectional and constant flow, which determines a physiologic shear stress, while arches and bifurcations are exposed to an oscillatory and disturbed flow, which determines a low shear stress. Atherosclerotic lesions develop mainly in areas of low shear stress, while those exposed to a physiologic shear stress are protected. The presence of areas of the arterial tree with different wall shear stress may explain, in part, the different localization of atherosclerotic lesions in both coronary and extracoronary arteries. The measurement of this parameter may help in identifying atherosclerotic plaques at higher risk as well as in evaluating the efficacy of different pharmacological interventions. Moreover, an altered shear stress is associated with the occurrence of both aortic and intracranial aneurysms, possibly leading to their growth and rupture. Finally, the evaluation of shear stress may be useful for predicting the risk of developing restenosis after coronary and peripheral angioplasty and for devising a coronary stent with a strut design less thrombogenic and more conducive to endothelization.
    Atherosclerosis 09/2010; 214(2):249-56. DOI:10.1016/j.atherosclerosis.2010.09.008 · 3.99 Impact Factor
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    • "The 3D voxel data obtained by rotational angiography were then transferred to a Dell 490 hemodynamic analysis workstation in our division. Image-based computational fluid dynamics (CFD) software developed by the Department of Computational Sciences, George Mason University, was utilized for aneurysm flow simulation [6, 7]. The 3D computational model was constructed semiautomatically through segmentation, surface generation, and 3D grid generation for each ICA–Oph aneurysm. "
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    ABSTRACT: Various anatomical parameters affect on intra-aneurysmal hemodynamics. Nevertheless, how the shapes of real patient aneurysms affect on their intra-aneurysmal hemodynamics remains unanswered. Quantitative computational fluid dynamics simulation was conducted using eight patients' angiograms of internal carotid artery-ophthalmic artery aneurysms. The mean size of the intracranial aneurysms was 11.5 mm (range 5.8 to 19.9 mm). Intra-aneurysmal blood flow velocity and wall shear stress (WSS) were collected from three measurement planes in each aneurysm dome. The correlation coefficients (r) were obtained between hemodynamic values (flow velocity and WSS) and the following anatomical parameters: averaged dimension of aneurysm dome, the largest aneurysm dome dimension, aspect ratio, and dome-neck ratio. Negative linear correlations were observed between the averaged dimension of aneurysm dome and intra-aneurysmal flow velocity (r= -0.735) and also WSS (r= -0.736). The largest dome diameter showed a negative correlation with intra-aneurysmal flow velocity (r= -0.731) and WSS (r= -0.496). The aspect ratio demonstrated a weak negative correlation with the intra-aneurysmal flow velocity (r= -0.381) and WSS (r= -0.501). A clear negative correlation was seen between the intra-aneurysmal flow velocity and the dome-neck ratio (r= -0.708). A weak negative correlation is observed between the intra-aneurysmal WSS and the dome-neck ratio (r= -0.392). The aneurysm dome size showed a negative linear correlation with intra-aneurysmal flow velocity and WSS. Wide-necked aneurysm geometry was associated with faster intra-aneurysmal flow velocity.
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    ABSTRACT: Flow velocity field, vorticity and circulation and wall shear stresses were simulated by FSI approach under conditions of pulsatile flow in a scale model of the rabbit elastin-induced aneurysm. The flow pattern inside the aneurysm sac confirmed the in vitro experimental findings that in diastole time period the flow inside the aneurysm sac is a stable circular clock-wise flow, while in systole time period higher velocity enters into the aneurysm sac and during systole and diastole time period an anti-clock circular flow pattern emerged near the distal neck; in the 3-D aneurysm sac, the kinetic energy per point is about 0.0002 (m2/s2); while in the symmetrical plane of the aneurysm sac, the kinetic energy per point is about 0.00024 (m2/s2). In one cycle, the shape of the intraaneurysmal energy profile is in agreement with the experimental data; The shear stress near the proximal neck experienced higher shear stress (peak value 0.35 Pa) than the distal neck (peak value 0.2 Pa), while in the aneurysm dome, the shear stress is always the lowest (0.0065 Pa). The ratio of shear stresses in the proximal neck vs. distal neck is around 1.75, similar to the experimental findings that the wall shear rate ratio of proximal neck vs. distal neck is 1.5 to 2.
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