Suppression of Wall Shear Stress inside Intracranial Aneurysms by Simple Stents

2018 ◽  
Vol 3 ◽  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Wall Shear

Early Cellular and Molecular Changes During Hemodynamic Initiation of Intracranial Aneurysms in a Rabbit Model

2010 ◽  
Author(s):  
Ling Gao ◽  
Max Mandelbaum ◽  
Nicholas Liaw ◽  
Sabareesh K. Natarajan ◽  
J. Mocco ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Molecular Mechanisms ◽  
Morphological Changes ◽  
Stress Gradient ◽  
Rabbit Model ◽  
Apical Region ◽  
Apical Side ◽  
Wall Shear

Hemodynamics constitutes a critical factor in the formation of intracranial aneurysms. However, little is known about how an intracranial arterial wall responds to a hemodynamic insult, and how that response contributes to aneurysm formation. Unlike straight arterial segments (which respond to increased flow by expansive remodeling) and sinuses opposing bifurcation apices (which harbor recirculation flows and are prone to atherosclerotic development), aneurysmal degeneration occurs on the apical side of the bifurcation in the immediate peri-apical region, where flow creates very high wall shear stress (WSS) and wall shear stress gradient (WSSG)1. This results in destructive aneurysmal remodeling, characterized by loss of the internal elastic lamina (IEL) and thinning of the media. It is unknown how the unique hemodynamic conditions of combined high WSS and positive WSSG elicit these morphological changes, how the vascular wall responds to such insult at the molecular level, and what molecular mechanisms are involved.

Morphological Effect on Wall Shear Stress in Intracranial Aneurysms

2017 ◽  
Vol 79 (02) ◽  
pp. 108-115 ◽  
Author(s):  
Tian-Lun Qiu ◽  
Guo-Liang Jin ◽  
Hai-Tao Lu ◽  
Wu-Qiao Bao
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Multivariable Analysis ◽  
Morphological Characteristics ◽  
Parent Artery ◽  
Parent Vessel ◽  
Morphological Effect ◽  
Neck Width ◽  
Wall Shear

Background and Study Aims Both high and low wall shear stress (WSS) play important roles in the development and rupture of intracranial aneurysms (IAs). This study aimed to determine the morphological factors that affect WSS in the IA and the parent artery. Material and Methods We studied a total of 66 IAs with three-dimensional imaging. Computational fluid dynamics (CFD) models were constructed and used to characterize the hemodynamics quantitatively. Aneurysms were grouped according to the mean neck width. The associations among hemodynamics and morphology were analyzed. Results Aspect ratio was correlated to lowest WSS (r = − 0.576), aneurysm-to-parent vessel (A-P) WSS ratio (r = − 0.500), and lowest-parent vessel (L-P) WSS ratio (r = − 0.575). Height-to-width ratio and height were correlated to WSS. Mean aneurysm WSS (p = 0.023), lowest WSS (p < 0.0001), highest-to-lowest WSS ratio (p = 0.004), L-P WSS ratio (p < 0.0001), highest-parent vessel (H-P) WSS ratio (p = 0.008), A-P WSS ratio (p < 0.001), and height (p < 0.001) were different between the two groups of aneurysms that were divided by the relationship between the diameters of the aneurysms and the necks. Multivariable analysis showed that the lowest WSS (p = 0.028) and A-P WSS ratio (p = 0.001) were independently associated with neck width. Conclusion Morphological characteristics are associated with IA and parent vessel WSS. Aneurysms with different neck widths have different hemodynamics. These results could help in understanding the progression of IA and in building predictive models for IA rupture.

scholarly journals Flow instability and wall shear stress variation in intracranial aneurysms

2009 ◽  
Vol 7 (47) ◽  
pp. 967-988 ◽  
Author(s):  
H. Baek ◽  
M. V. Jayaraman ◽  
P. D. Richardson ◽  
G. E. Karniadakis
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Flow Instability ◽  
Hydrodynamic Instability ◽  
Saccular Aneurysm ◽  
High Frequency Oscillation ◽  
Patient Specific ◽  
Parent Vessel ◽  
Wall Shear

We investigate the flow dynamics and oscillatory behaviour of wall shear stress (WSS) vectors in intracranial aneurysms using high resolution numerical simulations. We analyse three representative patient-specific internal carotid arteries laden with aneurysms of different characteristics: (i) a wide-necked saccular aneurysm, (ii) a narrower-necked saccular aneurysm, and (iii) a case with two adjacent saccular aneurysms. Our simulations show that the pulsatile flow in aneurysms can be subject to a hydrodynamic instability during the decelerating systolic phase resulting in a high-frequency oscillation in the range of 20–50 Hz, even when the blood flow rate in the parent vessel is as low as 150 and 250 ml min −1 for cases (iii) and (i), respectively. The flow returns to its original laminar pulsatile state near the end of diastole. When the aneurysmal flow becomes unstable, both the magnitude and the directions of WSS vectors fluctuate at the aforementioned high frequencies. In particular, the WSS vectors around the flow impingement region exhibit significant spatio-temporal changes in direction as well as in magnitude.

scholarly journals Wall Enhancement, Hemodynamics, and Morphology in Unruptured Intracranial Aneurysms with High Rupture Risk

2020 ◽  
Vol 11 (5) ◽  
pp. 882-889 ◽  
Author(s):  
Nan Lv ◽  
Christof Karmonik ◽  
Shiyue Chen ◽  
Xinrui Wang ◽  
Yibin Fang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Confidence Interval ◽  
Odds Ratio ◽  
Intracranial Aneurysms ◽  
Rupture Risk ◽  
Hemodynamic Pattern ◽  
Unruptured Intracranial Aneurysms ◽  
Wall Shear ◽  
The Relationship

Abstract The purpose of this study is to investigate the relationship between morphology, hemodynamics, and aneurysm wall enhancement (AWE) on vessel wall MRI and their potential role in rupture of intracranial aneurysms. Fifty-seven patients (22 males and 35 females; mean age of 58.4) harboring 65 unruptured intracranial aneurysms were retrospectively recruited. Vessel wall MRI images were reviewed and differentiated as no (NAWE), partial (PAWE), and circumferential (CAWE) wall enhancement. Computational geometry and computational fluid dynamics were used to calculate morphological and hemodynamic parameters. The PHASES score was calculated for each case to estimate its rupture risk. Univariate and multivariate logistic regression analysis was performed to investigate the relationship between morphological-hemodynamic pattern and AWE as well as their association with rupture risk. AWE was present in 26 (40.0%) lesions, including 14 (21.5%) PAWE and 12 (18.5%) CAWE. Aneurysm size (odds ratio = 7.46, 95% confidence interval = 1.56–35.77, p = 0.012), size ratio (odds ratio = 12.90, 95% confidence interval = 2.28–72.97, p = 0.004), and normalized wall shear stress (odds ratio = 0.11, 95% confidence interval = 0.02–0.69, p = 0.018) were independently associated with the presence of AWE. With increasing PHASES score, size-related parameters and the frequency of irregular shape increased significantly, and a hemodynamic pattern of lower and oscillating wall shear stress was observed. Simultaneously, the proportion of NAWE aneurysms decreased, and PAWE and CAWE aneurysms increased significantly (p < 0.001). Unruptured intracranial aneurysms with a higher rupture risk presented with a significantly larger size, lower wall shear stress, and more intense AWE, which might support the interaction between morphology, hemodynamics, and inflammation and their potential role in aneurysm rupture prediction.

Temporal variations of wall shear stress parameters in intracranial aneurysms—importance of patient-specific inflow waveforms for CFD calculations

2010 ◽  
Vol 152 (8) ◽  
pp. 1391-1398 ◽  
Author(s):  
Christof Karmonik ◽  
Christopher Yen ◽  
Orlando Diaz ◽  
Richard Klucznik ◽  
Robert G. Grossman ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Temporal Variations ◽  
Patient Specific ◽  
Wall Shear ◽  
Stress Parameters

Intracranial Aneurysms Occur More Frequently at Bifurcation Sites That Typically Experience Higher Hemodynamic Stresses

Neurosurgery ◽  
2013 ◽  
Vol 73 (3) ◽  
pp. 497-505 ◽  
Author(s):  
Jaclyn M. Alfano ◽  
John Kolega ◽  
Sabareesh K. Natarajan ◽  
Jianping Xiang ◽  
Rocco A. Paluch ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Stress Gradient ◽  
Spatial Gradient ◽  
Impact Zone ◽  
Wall Shear ◽  
A Site ◽  
The Impact ◽  
Hemodynamic Stresses

Abstract BACKGROUND: Intracranial aneurysms (IAs) occur more frequently at certain bifurcations than at others. Hemodynamic stress, which promotes aneurysm formation in animal models, also differs among bifurcations, depending on flow and vessel geometry. OBJECTIVE: To determine whether locations that are more likely to develop IAs experience different hemodynamic stresses that might contribute to higher IA susceptibility. METHODS: We characterized the hemodynamic microenvironment at 10 sites in or around the circle of Willis where IAs commonly occur and examined statistical relationships between hemodynamic factors and the tendency for a site to form IAs. The tendency for each site to develop IAs was quantified on the basis of the site distribution from systematic literature analysis of 19 reports including 26 418 aneurysms. Hemodynamic parameters for these sites were derived from image-based computational fluid dynamics of 114 cerebral bifurcations from 31 individuals. Wall shear stress and its spatial gradient were calculated in the impact zone surrounding the bifurcation apex. Linear and exponential regression analyses evaluated correlations between the tendency for IA formation and the typical hemodynamics of a site. RESULTS: IA susceptibility significantly correlated with the magnitudes of wall shear stress and positive wall shear stress gradient within the hemodynamic impact zone calculated for each site. CONCLUSION: IAs occur more frequently at cerebral bifurcations that typically experience higher hemodynamic shear stress and stronger flow acceleration, conditions previously shown to promote aneurysm initiation in animals.

Towards Deep Learning-based Wall Shear Stress Prediction for Intracranial Aneurysms

2021 ◽  
pp. 105-110
Author(s):  
Annika Niemann ◽  
Lisa Schneider ◽  
Bernhard Preim ◽  
Samuel Voß ◽  
Philipp Berg ◽  
...  
Keyword(s):  
Shear Stress ◽  
Deep Learning ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Stress Prediction ◽  
Wall Shear

Hemodynamic differences between unstable and stable unruptured aneurysms independent of size and location: a pilot study

2016 ◽  
Vol 9 (4) ◽  
pp. 376-380 ◽  
Author(s):  
Waleed Brinjikji ◽  
Bong Jae Chung ◽  
Carlos Jimenez ◽  
Christopher Putman ◽  
David F Kallmes ◽  
...  
Keyword(s):  
Shear Stress ◽  
Pilot Study ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Wilcoxon Test ◽  
Patient Specific ◽  
Unruptured Aneurysms ◽  
Unruptured Intracranial Aneurysms ◽  
Wall Shear ◽  
Geometric Variables

BackgroundWhile clinical and angiographic risk factors for intracranial aneurysm instability are well established, it is reasonable to postulate that intra-aneurysmal hemodynamics also have a role in aneurysm instability.ObjectiveTo identify hemodynamic characteristics that differ between radiologically unstable and stable unruptured intracranial aneurysms.Materials and methods12 pairs of unruptured intracranial aneurysms with a 3D rotational angiographic set of images and followed up longitudinally without treatment were studied. Each pair consisted of one stable aneurysm (no change on serial imaging) and one unstable aneurysm (demonstrated growth of at least 1 mm diameter or ruptured during follow-up) of matching size (within 10%) and locations. Patient-specific computational fluid dynamics models were created and run under pulsatile flow conditions. Relevant hemodynamic and geometric variables were calculated and compared between groups using the paired Wilcoxon test.ResultsThe area of the aneurysm under low wall shear stress (low shear stress area (LSA)) was 2.26 times larger in unstable aneurysms than in stable aneurysms (p=0.0499). The mean aneurysm vorticity was smaller by a factor of 0.57 in unstable aneurysms compared with stable aneurysms (p=0.0499). No statistically significant differences in geometric variables or shape indices were found.ConclusionsThis pilot study suggests there may be hemodynamic differences between unstable and stable unruptured cerebral aneurysms. In particular, the area under low wall shear stress was larger in unstable aneurysms. These findings should be considered tentative until confirmed by future larger studies.

The Role of One-Dimensional Model-Generated Inter-Subject Variations in Systemic Properties on Wall Shear Stress Indices of Intracranial Aneurysms

2020 ◽  
Vol 67 (4) ◽  
pp. 1030-1039
Author(s):  
Raoul R. F. Stevens ◽  
Wouter P. Donders ◽  
Sjeng Quicken ◽  
Frans N. van de Vosse ◽  
Werner H. Mess ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Dimensional Model ◽  
Stress Indices ◽  
One Dimensional ◽  
Wall Shear
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