Patient-specific flow analysis of brain aneurysms at a single location: comparison of hemodynamic characteristics in small aneurysms.
ABSTRACT 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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ABSTRACT: Biofluid mechanics is increasingly applied in support of diagnosis and decision-making for treatment of clinical pathologies. Exploring the relationship between blood flow phenomena and pathophysiological observations is enhanced by continuing advances in the imaging modalities, measurement techniques, and capabilities of computational models. When combined with underlying physiological models, a powerful set of tools becomes available to address unmet clinical needs, predominantly in the direction of enhanced diagnosis, as well as assessment and prediction of treatment outcomes. This position paper presents an overview of current approaches and future developments along this theme that were discussed at the 5th International Biofluid Symposium and Workshop held at the California Institute of Technology in 2008. The introduction of novel mechanical biomarkers in device design and optimization, and applications in the characterization of more specific and focal conditions such as aneurysms, are at the center of attention. Further advances in integrative modeling, incorporating multiscale and multiphysics techniques are also discussed.Annals of Biomedical Engineering 03/2010; 38(3):1216-24. · 3.23 Impact Factor
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ABSTRACT: Flow impingement is regarded as a key factor for aneurysm formation and rupture. Wall shear stress (WSS) is often used to evaluate flow impingement even though WSS and impinging force are in two different directions; therefore, this raises an important question of whether using WSS for evaluation of flow impingement size is appropriate. Flow impinging behavior in a patient-specific model of a giant aneurysm (GA) at the internal carotid artery (ICA) was analyzed by computational fluid dynamics simulations. An Impingement Index (IMI) was used to evaluate the timing and size of flow impingement. In theory, the IMI is related to the WSS gradient, which is known to affect vascular biology of endothelial cells. Effect of non-Newtonian fluid, aneurysm size, and heart rate were also studied. Maximum WSS is found to be proportional to the IMI, but the area of high wall shear is not proportional to the size of impingement. A faster heart rate or larger aneurysm does not produce a larger impinging site, and the Newtonian assumption overestimates the size of impingement. Flow impingement at the dome occurs approximately 0.11 s after the peak of flow waveform is attained. This time delay also increases with aneurysm size and varies with heart rate and waveform.Medical & Biological Engineering 01/2011; 49(8):891-9. · 1.76 Impact Factor
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ABSTRACT: The purpose of this article is to review studies of aneurysm risk factors and the suggested hypotheses that connect the different risk factors and the underlying mechanisms governing the aneurysm natural history. The result of this work suggests that at the center of aneurysm evolution there is a cycle of wall degeneration and weakening in response to changing hemodynamic loading and biomechanic stress. This progressive wall degradation drives the geometrical evolution of the aneurysm until it stabilizes or ruptures. Risk factors such as location, genetics, smoking, co-morbidities, and hypertension seem to affect different components of this cycle. However, details of these interactions or their relative importance are still not clearly understood.Annals of Biomedical Engineering 12/2012; · 3.23 Impact Factor