Simulation analysis of aneurysm embolization surgery: Hemorheology of aneurysms with different embolization rates (CTA)

BACKGROUND: Embolization degree acts as an important factor affecting recurrence of aneurysm. OBJECTIVE: To analyze the role of hemodynamics parameters of different degrees of embolization in the occurrence, development and post-treatment of aneurysms, and to determine the specific factors causing the occurrence and recurrence of aneurysms after hemodynamics treatment. Our study provides a theoretical basis for the prevention and treatment of aneurysms. METHODS: Computed Tomography Angiography (CTA) data of a patient with cerebral aneurysm were used to model 0%, 24%, 52%, 84% and 100% of endovascular embolization, respectively. The time average wall shear stress, time average wall shear stress, oscillatory shear index, hemodynamics formation index and relative retentive time were used to analyze the changes of hemodynamics indexes in different embolic models. RESULTS: With the increase of embolic rate, the values of time average wall shear stress, time average wall shear stress grade and aneurysm index formation gradually increased, and the values of relative retention time gradually decreased. Oscillatory shear index was higher in patients with incomplete embolization and decreased in patients with complete embolization. CONCLUSIONS: As the degree of embolization increased, the blood flow tended to stabilize, reducing the risk of cerebral aneurysm rupture, and finding that the wall of the vessel junction was susceptible to injury.

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Effects of smoking and hypertension on wall shear stress and oscillatory shear index at the site of intracranial aneurysm formation

Clinical Neurology and Neurosurgery ◽

10.1016/j.clineuro.2009.12.018 ◽

2010 ◽

Vol 112 (4) ◽

pp. 306-313 ◽

Cited By ~ 37

Author(s):

Pankaj K. Singh ◽

Alberto Marzo ◽

Bethany Howard ◽

Daniel A. Rufenacht ◽

Philippe Bijlenga ◽

...

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Intracranial Aneurysm ◽

Oscillatory Shear ◽

Oscillatory Shear Index ◽

Aneurysm Formation ◽

Wall Shear

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3D Quantification of Wall Shear Stress and Oscillatory Shear Index Using a Finite-Element Method in 3D CINE PC-MRI Data of the Thoracic Aorta

IEEE Transactions on Medical Imaging ◽

10.1109/tmi.2016.2517406 ◽

2016 ◽

Vol 35 (6) ◽

pp. 1475-1487 ◽

Cited By ~ 16

Author(s):

Julio Sotelo ◽

Jesus Urbina ◽

Israel Valverde ◽

Cristian Tejos ◽

Pablo Irarrazaval ◽

...

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Shear Stress ◽

Wall Shear Stress ◽

Thoracic Aorta ◽

Oscillatory Shear ◽

Oscillatory Shear Index ◽

Wall Shear ◽

Element Method

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Numerical insights into the determinants of stent performance for the management of aneurysm with a visceral vessel attached

Acta of Bioengineering and Biomechanics ◽

10.37190/abb-01748-2020-03 ◽

2021 ◽

Vol 23 (2) ◽

Author(s):

Zhongyou Li ◽

Chong Chen ◽

Yu Chen ◽

Zhenze Wang ◽

Wentao Jiang ◽

...

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Pore Size ◽

Residence Time ◽

Single Layer ◽

Oscillatory Shear ◽

Bending Test ◽

Oscillatory Shear Index ◽

Relative Residence Time ◽

Wall Shear

Purpose: As the factors affecting the efficacy of the bare-metal stent in the treatment of aneurysm with a visceral vessel attached were not fully understood, we aimed to discuss the effects of different characteristics of the stent on the hemodynamics and flexibility in the treatment of the aneurysm. Methods: Single-layer (with different strut widths) and multi-layer (with a different number of struts) stent models divided into three porosity groups, with porosities of 72.3, 60.5, and 52.4%, were modeled for a comparison of their hemodynamic isolation and flexibility performance via computational fluid dynamics and finite element methods. Results: The velocity and timeaveraged wall shear stress decreased more noticeably with multi-layer stent interventions. A higher oscillatory shear index and relative residence time occurred at the aneurysmal sac wall after multi-layer stents were employed. Time-averaged wall shear stress on the aneurysmal wall decreased with an increase in the number of struts or a decrease in pore size, but oscillatory shear index and relative residence time increased as the number of struts increased or the pore size decreased. Besides, all stents affect the branch patency slightly. In the bending test, when the porosity exceeded 60.5%, multi-layer stents were more flexible. Conclusion: The number of struts or pore size of stent dominated the isolation in the management of the aneurysm and affected the flexibility significantly when the porosity was below 60.5%. These findings may contribute to the special design of the stent in the treatment of such types of aneurysms.

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Distinctive flow pattern of wall shear stress and oscillatory shear index: similarity and dissimilarity in ruptured and unruptured cerebral aneurysm blebs

Journal of Neurosurgery ◽

10.3171/2012.7.jns111991 ◽

2012 ◽

Vol 117 (4) ◽

pp. 774-780 ◽

Cited By ~ 47

Author(s):

Tomohiro Kawaguchi ◽

Shinjitsu Nishimura ◽

Masayuki Kanamori ◽

Hiroki Takazawa ◽

Shunsuke Omodaka ◽

...

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Unruptured Aneurysm ◽

Oscillatory Shear ◽

Oscillatory Shear Index ◽

Unruptured Aneurysms ◽

Unruptured Cerebral Aneurysm ◽

Thin Walled ◽

Wall Shear ◽

The Difference

Object The difference in the hemodynamics of wall shear stress (WSS) and oscillatory shear index (OSI) between ruptured and unruptured aneurysms is not well understood. The authors investigated the hemodynamic similarities and dissimilarities in ruptured and thin-walled unruptured aneurysm blebs. Methods Magnetic resonance imaging–based fluid dynamics analysis was used to calculate WSS and OSI, and hemodynamic and intraoperative findings were compared. The authors also compared ruptured and unruptured thin-walled blebs for the magnitude of WSS and OSI. Results Intraoperatively, 13 ruptured and 139 thin-walled unruptured aneurysm blebs were identified. Twelve of the ruptured (92.3%) and 124 of the unruptured blebs (89.2%) manifested low WSS and high OSI. The degree of WSS was significantly lower in ruptured (0.49 ± 0.12 Pa) than in unruptured (0.64 ± 0.15 Pa; p < 0.01) blebs. Conclusions Ruptured and unruptured blebs shared a distinctive pattern of low WSS and high OSI. The degree of WSS at the rupture site was significantly lower than in the unruptured thin-walled blebs.

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Effects of waveform shape of pulsatile blood flow on hemodynamics in an artery bifurcation model

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406220911397 ◽

2020 ◽

pp. 095440622091139

Author(s):

Qiuxiang Huang ◽

Jianhong Sun ◽

Changyue Xu

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Local Maximum ◽

Oscillatory Shear ◽

Oscillatory Shear Index ◽

Flow Waveform ◽

Mean Velocity ◽

Steady State Condition ◽

Wall Shear ◽

The Impact

Pulsatile non-Newtonian fluid flow was simulated in an artery bifurcation model, with three different inlet flow waveform shapes and an identical inlet mean velocity steady-state condition, to quantify the impact of three different waveform shapes on hemodynamics such as flow patterns, wall shear stress, and oscillatory shear index during a cardiac cycle. It was found that the degree of flow separation is insensitive to changes in flow waveform shape. There is remarkable similarity in the position and magnitude of the maximum wall shear stress at peak systole and the maximum time-averaged wall shear stress for all examined cases. The oscillatory shear index distributions are broadly similar except that the local maximum oscillatory shear index increases proportionally with the pulsatility index of the waveform shape. The maximum oscillatory shear index values on the planar branch are within 8.7% in all examined cases, while these oscillatory shear index values on the nonplanar branch are identical due to the effects of its curvature. The negligible hemodynamic differences between simplified and characteristic waveform cases suggest that changes in waveform shape play a minimal role in the progression and development of atherosclerosis. Although the computed hemodynamics is almost consistent for the three different waveform shapes, several slight differences were observed.

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WALL SHEAR STRESS AND OSCILLATORY SHEAR INDEX DISTRIBUTION IN CAROTID ARTERY WITH VARYING DEGREE OF STENOSIS: A HEMODYNAMIC STUDY

Journal of Mechanics in Medicine and Biology ◽

10.1142/s0219519417500373 ◽

2017 ◽

Vol 17 (02) ◽

pp. 1750037 ◽

Cited By ~ 7

Author(s):

PRASHANTH BASAVARAJA ◽

ANISH SURENDRAN ◽

AJAY GUPTA ◽

LUCA SABA ◽

JOHN R. LAIRD ◽

...

Keyword(s):

Shear Stress ◽

Carotid Artery ◽

Wall Shear Stress ◽

Plaque Rupture ◽

Significant Proportion ◽

Oscillatory Shear ◽

Cerebral Stroke ◽

Spatial Average ◽

Oscillatory Shear Index ◽

Wall Shear

A significant proportion of cerebral stroke is a consequence of the arterial stenotic plaque rupture causing local thrombosis or distal embolization. The formation and subsequent rupture of the plaque depends on wall shear stress (WSS) and oscillatory shear index (OSI). The purpose of the present study was to understand the effect of hemodynamics on the spatial and temporal variations of WSS and OSI using realistic models with varying degree of carotid artery stenosis (DOS). Multiple CT volumes were obtained from subjects in the carotid bifurcation zone and the 3D models were generated. A finite volume-based computational fluid dynamics (CFD) method was utilized to understand the hemodynamics in pulsatile flow conditions. It was observed that high stenosis models occupied a large value of normalized WSS in the internal carotid artery (ICA) whereas they had smaller values of normalized WSS in the common carotid artery (CCA). For clinical use, the authors recommend using the spatial average value of oscillatory shear rather than the maximum value for an accurate knowledge about the severity of stenosis. The resultant vorticity changes the direction of spin after the bifurcation zone. Additionally, we propose the use of limiting streamlines as a novel and convenient method to identify the disturbed flow regions that are prone to atherogenesis.

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Evaluation of Modified Oscillatory Shear Index and Recirculation Zone in a Deployed Coronary Stent

Advances in Bioengineering ◽

10.1115/imece2004-61269 ◽

2004 ◽

Author(s):

Divakar Rajamohan ◽

Ashraf A. Ibrahim ◽

Lloyd H. Back ◽

Milind A. Jog ◽

Rupak K. Banerjee

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Computational Study ◽

Oscillatory Shear ◽

Oscillatory Shear Index ◽

Neointimal Formation ◽

Factors Affecting ◽

Stent Strut ◽

Flow Through ◽

Wall Shear

A major consequence of stent implantation is restenosis which occurs due to neointimal formation. There are several factors affecting restenosis among which wall shear stress plays a significant role. The present computational study of developing pulsatile flow through the entrance region of a deployed Palmaz stent in a coronary artery analyzes the local wall shear distribution and its effect on restenosis. A variation from low positive wall shear stress of around 10 dyn/cm2 at the upstream of stent strut intersection to a very high positive wall shear stress of 300 dyn/cm2 at strut intersection and then to a negative wall shear stress of −10 dyn/cm2 at the downstream of strut intersection was observed. Modified oscillatory shear index was calculated which showed persistent recirculation at the downstream of strut intersection indicating it as a highly prone region to restenosis.

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Non-Newtonian Blood Modeling in Intracranial Aneurysm Hemodynamics: Impact On the WSS and OSI Metrics for Ruptured and Unruptured Cases

Journal of Biomechanical Engineering ◽

10.1115/1.4050539 ◽

2021 ◽

Author(s):

Iago Oliveira ◽

Gabriel B Santos ◽

José Luiz Gasche ◽

Julio Militzer ◽

Carlos Eduardo Baccin

Keyword(s):

Blood Flow ◽

Shear Stress ◽

Wall Shear Stress ◽

Oscillatory Shear ◽

Patient Specific ◽

Oscillatory Shear Index ◽

Hemodynamic Variables ◽

Flow Parameters ◽

Newtonian Model ◽

Wall Shear

Abstract When simulating blood flow in intracranial aneurysms, the Newtonian model seems to be ubiquitous. However, analyzing the results from the few studies on this subject, the doubt remains on whether it is necessary to use non-Newtonian models in wall shear stress (WSS) simulations of cerebral vascular flows. Another open question related to this topic is whether different rheology models would influence the flow parameters for ruptured and unruptured cases, especially because ruptured aneurysms normally have morphological features that could trigger non-Newtonian phenomena in the blood flow due to low shear rates. The objective of this study is to investigate such flows. By using Computational Fluid Dynamics (CFD) in an open-source framework, we simulated an equal number of ruptured and unruptured patient-specific aneurysms to assess the influence of the blood modeling on the main hemodynamic variables associated with aneurysm formation, growth, and rupture. Results for wall shear stress and oscillatory shear index and their metrics were obtained using Casson and Carreau-Yasuda non-Newtonian models and were compared with those obtained using the Newtonian model. We found that the wall shear stress at peak systole is overestimated by more than 50% by using the non-Newtonian models, but its metrics based on time and surface averaged values remain unaffected. On the other hand, the surface-averaged oscillatory shear index (OSI) is underestimated by more than 40% by the non-Newtonian models. In addition, all differences were consistent among all aneurysms cases irrespective of their rupture status.

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Hemodynamics Modeling and Simulation of Anterior Communicating Artery Aneurysms

Advances in Mechanical Engineering ◽

10.1155/2014/908357 ◽

2014 ◽

Vol 6 ◽

pp. 908357 ◽

Cited By ~ 1

Author(s):

Jianjun Li ◽

Shengzhang Wang ◽

Gang Lu ◽

Xiaolong Zhang

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Cerebral Aneurysms ◽

Artery Aneurysm ◽

Oscillatory Shear ◽

Anterior Communicating Artery ◽

Rupture Risk ◽

Oscillatory Shear Index ◽

Anterior Communicating Artery Aneurysms ◽

Wall Shear

It is a general agreement that hemodynamics plays very important role in the initiation, growth, and rupture of cerebral aneurysms and hemodynamics in the anterior communicating artery aneurysms is considered the most complex in all cerebral aneurysms and it is difficult to find some reasonable relationship between the hemodynamics parameters and the rupture risk. In this paper, the 3D geometries of four anterior communicating artery aneurysms were generated from the CTA data and the computational models with bilateral feeding arteries for the four aneurysms were constructed. The blood flow was simulated by computational fluid dynamics software and the hemodynamics parameters such as velocity, wall shear stress, and oscillatory shear index were calculated. The following results were observed: one of the four models only needs the left feeding artery; the max normalized wall shear stress locates at the aneurysmal neck of the largest aneurysm; the max oscillatory shear index locates at the aneurysmal sac of the largest aneurysm. The conclusion was drawn that the anterior communicating artery aneurysm has higher rupture risk from the hemodynamics viewpoint if the max wall shear stress locates at the neck and the max oscillatory shear index locates at the dome.

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