Hemodynamics of small aneurysm pairs at the internal carotid artery (original) (raw)
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The effect of aneurysm geometry on the intra-aneurysmal flow condition
2010
Introduction Various anatomical parameters affect on intraaneurysmal hemodynamics. Nevertheless, how the shapes of real patient aneurysms affect on their intra-aneurysmal hemodynamics remains unanswered. Methods 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.
Hemodynamic Patterns of Anterior Communicating Artery Aneurysms: A Possible Association with Rupture
American Journal of Neuroradiology, 2008
BACKGROUND AND PURPOSE: The anterior communicating artery (AcomA) is a predilect location of aneurysms which typically carry higher rupture risks than other locations in the anterior circulation. The purpose of this study was to characterize the different flow types present in AcomA aneurysms and to investigate possible associations with rupture. MATERIALS AND METHODS: Patient-specific computational models of 26 AcomA aneurysms were constructed from 3D rotational angiography images. Bilateral images were acquired in 15 patients who had both A1 segments of the anterior cerebral arteries, and models of the whole anterior circulation were created by fusing the reconstructed left and right arterial trees. Computational fluid dynamics simulations were performed under pulsatile flow conditions measured on a healthy subject. Visualizations of flow velocity, instantaneous streamlines, and wall shear stress (WSS) were performed. These were analyzed for flow patterns, size of the impaction zone, and peak WSS and then correlations were made with prior history of rupture. RESULTS: Aneurysms with small impaction zones were more likely to have ruptured than those with large impaction zones (83% versus 63%). Maximum intra-aneurysmal WSS (MWSS) for the unruptured aneurysms ranged from 10 to 230 dyne/cm 2 (mean, 114 dyne/cm 2) compared with ruptured aneurysms, which ranged from 35 to 1500 dyne/cm 2 (mean, 271 dyne/cm 2). This difference in MWSS was statistically significant at 90% confidence levels (P ϭ .10). CONCLUSIONS: Aneurysms with small impaction zones, higher flow rates entering the aneurysm, and elevated MWSS are associated with a clinical history of previous rupture.
Impact of aneurysmal geometry on intraaneurysmal flow: a computerized flow simulation study
Neuroradiology, 2008
Introduction This study was performed to assess the effect of aneurysm geometry on parameters that may have an impact on the natural history of intracranial aneurysms, such as intraaneurysmal flow pressure and shear stress. Methods Flow was simulated in 21 randomly selected aneurysms using finite volume modeling. Ten aneurysms were classified as side-wall aneurysms, with either singlesided or circumferential involvement of the parent artery wall, and 11 as bifurcation aneurysms (symmetric or asymmetric), with an axis either perpendicular or parallel to the parent artery. The flow patterns were classified as either jet or vortex types (with regular or irregular vortex flow). Pressures and shear stresses were characterized as evenly or unevenly distributed over the aneurysm wall and neck. Results All side-wall and four of the bifurcation aneurysms with a perpendicular axis had a vortex type flow pattern and seven bifurcation aneurysms with a parallel axis (four symmetric and two asymmetric) had a jet flow pattern. Jet type flow was associated with an uneven pressure distribution in seven out of seven aneurysms. Vortex type flow resulted in an even pressure distribution in five out of six aneurysms with an irregular flow pattern and six out of eight with a regular flow pattern. No firm relationship could be established between any geometrical type and shear stress distribution. Only 1 of 14 aneurysms with a perpendicular axis, but 4 of 7 aneurysms with a parallel axis, had ruptured. Conclusion Aneurysm geometry does have an impact on flow conditions. Aneurysms with a main axis parallel to the parent artery have a tendency to have a jet flow pattern and uneven distribution of unsteady pressure. These aneurysms may have a higher rate of rupture as than those with a main axis perpendicular to the parent artery.
Hemodynamics and Rupture of Terminal Cerebral Aneurysms
Academic Radiology, 2009
Rationale and Objectives. The objective of this study was to investigate the relationship between hemodynamics patterns and aneurysmal rupture in cerebral aneurysms of the same morphology regardless their location. Particularly, terminal aneurysms in both the anterior and posterior circulation were studied. Materials and Methods. A total of 42 patient-specific vascular models were constructed from three-dimensional rotational angiography images. All patients had terminal aneurysms at different arteries: a) middle cerebral; b) anterior communicating; c) internal carotid (terminus); d) internal carotid-posterior communicating; e) basilar; or f) anterior cerebral. Hemodynamics information (intra-aneurysmal velocity and wall shear stress distributions) was derived from image-based computational fluid dynamics models with realistic patient-specific anatomies. Results. The group of aneurysms with an inflow jet that splits in two secondary jets, one of which enters the aneurysm before reaching one of the daughter vessels (type B), had the highest peak wall shear stress (WSS) and the highest rupture rate. The peak WSS averaged over each flow type showed a higher value in the ruptured group. The average peak WSS in the ruptured group (all types) was 188 dyn/cm 2 (compared to 118 dyn/cm 2 for the unruptured). Conclusions. This finding is in agreement with a previous work in which only anterior communicating artery aneurysms were investigated. The significance of these findings is that, if they are statistically confirmed with larger number of cases, flow types could be directly observed during angiographic examinations and linked to WSS categories that may help evaluate which aneurysms are more likely to rupture.
Srpski arhiv za celokupno lekarstvo, 2013
Introduction. Natural course of aneurysms that occur on blood vessels of the brain singles out the need for understanding the mechanism of the occurrence of aneurysm wall rupture and identification of anatomic characteristics as predictive factors for hemorrhage to occur. Objective. In this study we comparatively present results of our researches and experimental models on animals. Methods. We made a comparative analysis of anatomical characteristics of blood vessels of the brain and aneurysms obtained on the basis of digital subtraction angiography and intraoperative finding. In this article we review recent research in the anatomic characteristics of intracranial aneurysms and parent blood vessels. We present a series of 185 aneurysms (ruptured and unruptured) dissected at the Neurosurgical Clinic of Clinical Center of Serbia in Belgrade. Results. Inclination angle may be considered as the vital predesposing factor for intracranial aneurysm rupture. In aneurysms that ruptured it w...
2012
BACKGROUND AND PURPOSE: EL associated with ruptured aneurysms is higher than that for unruptured aneurysms. In this study, the effect of arterial morphologic variation of bifurcation aneurysms on EL was investigated in idealized models of middle cerebral artery aneurysms. MATERIALS AND METHODS: Bifurcation angle configuration and DA ratio were evaluated in 6 idealized numeric models. Type A and B bifurcation models were defined with symmetric and asymmetric bifurcation angles of 136°, and 57°and 79°, respectively. Three models with DA ratios of 1, 1.3, and 2 were constructed for each type. EL was calculated as the energy difference between aneurysm inflow and outflow at the aneurysm neck. Three growth paths (R1, R2, and R3) were proposed. RESULTS: The highest EL and influx occurred in bifurcations with DA ratios of 1 for both types A and B. As the DA ratio increases, flow distribution between branches becomes more asymmetric, resulting in a reduction of EL and intra-aneurysmal flow. No strong relation was found between bifurcation angle configuration, inflow flux, and EL. EL decreased with an increase in the AR and DA ratio and increased with an increase in the AR and reduction of DA ratio. CONCLUSIONS: EL determined in idealized models is less dependent on bifurcation angle configuration than on DA ratio, and the stability of the aneurysm strongly depends on variation of the daughter artery morphology after aneurysm growth. ABBREVIATIONS: AR ϭ aspect ratio; DA ϭ daughter artery diameter; EL ϭ energy loss; LSA ϭ low shear stress area; R1 ϭ increasing the AR and DA ratio; R2 ϭ increasing the AR and reducing the DA ratio; R3 ϭ increasing the AR with a constant DA ratio; WSS ϭ wall shear stress
Basic principles of hemodynamics and cerebral aneurysms
World Neurosurgery, 2016
Rupture is the most serious consequence of cerebral aneurysms, and its likelihood depends on non-modifiable and modifiable risk factors. Recent efforts have focused on analyzing the effects of hemodynamic forces on the initiation, growth and rupture of cerebral aneurysms. Studies of role of hemodynamics on the physiopathology of intracranial aneurysms fall between mechanical engineering and molecular biology. This review is intended to summarize the basic principles of the effect of hemodynamic forces on the cerebral vascular wall. Nowadays, the size of the aneurysm dome is the most common parameter used in clinical practice to estimate the risk of rupture. However, relying only on aneurysm size means excessively simplifying a more complicated reality. Aneurysms emerge in areas of the vascular wall exposed to high wall shear stress. The direction that blood flows once an aneurysm forms depends on aspects such as neck diameter, its angle with respect to the parent artery, the parent vessel caliber, the caliber or the angle of efferent vessels, and aneurysm shape. The progression and rupture of aneurysms have been associated with zones of the aneurysm wall exposed to both high and low wall shear stresses. Advances in this challenging and growing field are intended to predict more precisely the risk of rupture of aneurysms and to better understand the mechanisms of origin and growth of aneurysms.
Aps Division of Fluid Dynamics Meeting Abstracts, 2010
Cerebral aneurysm formation is the result of a complex interplay of systemic and local factors. Among the latter, the role of the geometry of the vessel hosting an aneurysm, of the upstream vasculature and the induced hemodynamics still need to be carefully investigated. In this paper we combine computational fluid dynamics analysis and morphological characterization and carry out the statistical investigation of the features of the internal carotid artery (ICA) of 52 patients affected by a cerebral aneurysm. The functional principal component analysis performed on the geometric and fluid dynamics features of the patients reveals correlations with the location of the aneurysm in the cerebral circulation and its rupture status. This allows a clustering of the patients that is anticipated to contribute to the design of an index for the rupture risk. In particular, ICA featuring a pronounced WSS peak are statistically inclined to hosting ruptured aneurysms. Moreover, our statistical results suggest that patients with a double-bend siphons (S-class) are less prone to the development of cerebral aneurysms.
Quantitative Hemodynamic Analysis of Brain Aneurysms at Different Locations
American Journal of Neuroradiology, 2009
Studies have shown that the occurrence of brain aneurysms and risk of rupture vary between locations. However, the reason that aneurysms at different branches of the cerebral arteries have different clinical presentations is not clear. Because research has indicated that aneurysm hemodynamics may be one of the important factors related to aneurysm growth and rupture, our aim was to analyze and compare the flow parameters in aneurysms at different locations.