Non-Newtonian Computational Hemodynamics in Two Patient-Specific Cerebral Aneurysms with Daughter Saccules

Computational fluid dynamics (CFD) has grown as a tool to help understand the hemodynamic properties related to the rupture of cerebral aneurysms. Few of these studies deal specifically with aneurysm growth and most only use a single time instance within the aneurysm growth history. The present retrospective study investigated four patient-specific aneurysms, once at initial diagnosis and then at follow-up, to analyze hemodynamic and morphological changes. Aneurysm geometries were segmented via the medical image processing software Mimics. The geometries were meshed and a computational fluid dynamics (CFD) analysis was performed using ANSYS. Results showed that major geometry bulk growth occurred in areas of low wall shear stress (WSS). Wall shape remodeling near neck impingement regions occurred in areas with large gradients of WSS and oscillatory shear index. This study found that growth occurred in areas where low WSS was accompanied by high velocity gradients between the aneurysm wall and large swirling flow structures. A new finding was that all cases showed an increase in kinetic energy from the first time point to the second, and this change in kinetic energy seems correlated to the change in aneurysm volume.

Download Full-text

Optimal B-Spline Mapping of Flow Imaging Data for Imposing Patient-Specific Velocity Profiles in Computational Hemodynamics

IEEE Transactions on Biomedical Engineering ◽

10.1109/tbme.2018.2880606 ◽

2019 ◽

Vol 66 (7) ◽

pp. 1872-1883 ◽

Cited By ~ 2

Author(s):

Alberto Gomez ◽

Marija Marcan ◽

Christopher J. Arthurs ◽

Robert Wright ◽

Pouya Youssefi ◽

...

Keyword(s):

Velocity Profiles ◽

Patient Specific ◽

Flow Imaging ◽

Imaging Data ◽

B Spline ◽

Computational Hemodynamics

Download Full-text

Cerebral Aneurysms: A Patient-Specific and Image-Based Management Pipeline

Computational Methods in Applied Sciences - Computational Vision and Medical Image Processing ◽

10.1007/978-94-007-0011-6_19 ◽

2010 ◽

pp. 327-349 ◽

Cited By ~ 2

Author(s):

M. C. Villa-Uriol ◽

I. Larrabide ◽

J. M. Pozo ◽

M. Kim ◽

M. De Craene ◽

...

Keyword(s):

Cerebral Aneurysms ◽

Patient Specific

Download Full-text

Exploring High Frequency Temporal Fluctuations in the Terminal Aneurysm of the Basilar Bifurcation

Journal of Biomechanical Engineering ◽

10.1115/1.4007279 ◽

2012 ◽

Vol 134 (9) ◽

Cited By ~ 15

Author(s):

Matthew D. Ford ◽

Ugo Piomelli

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

High Frequency ◽

Cerebral Aneurysms ◽

Patient Specific ◽

Disturbed Flow ◽

Frequency Fluctuations ◽

Wall Shear ◽

Inflow Jet

Cerebral aneurysms are a common cause of death and disability. Of all the cardiovascular diseases, aneurysms are perhaps the most strongly linked with the local fluid mechanic environment. Aside from early in vivo clinical work that hinted at the possibility of high-frequency intra-aneurysmal velocity oscillations, flow in cerebral aneurysms is most often assumed to be laminar. This work investigates, through the use of numerical simulations, the potential for disturbed flow to exist in the terminal aneurysm of the basilar bifurcation. The nature of the disturbed flow is explored using a series of four idealized basilar tip models, and the results supported by four patient specific terminal basilar tip aneurysms. All four idealized models demonstrated instability in the inflow jet through high frequency fluctuations in the velocity and the pressure at approximately 120 Hz. The instability arises through a breakdown of the inflow jet, which begins to oscillate upon entering the aneurysm. The wall shear stress undergoes similar high-frequency oscillations in both magnitude and direction. The neck and dome regions of the aneurysm present 180 deg changes in the direction of the wall shear stress, due to the formation of small recirculation zones near the shear layer of the jet (at the frequency of the inflow jet oscillation) and the oscillation of the impingement zone on the dome of the aneurysm, respectively. Similar results were observed in the patient-specific models, which showed high frequency fluctuations at approximately 112 Hz in two of the four models and oscillations in the magnitude and direction of the wall shear stress. These results demonstrate that there is potential for disturbed laminar unsteady flow in the terminal aneurysm of the basilar bifurcation. The instabilities appear similar to the first instability mode of a free round jet.

Download Full-text

Hemodynamic conditions that favor bleb formation in cerebral aneurysms

Journal of NeuroInterventional Surgery ◽

10.1136/neurintsurg-2020-016369 ◽

2020 ◽

pp. neurintsurg-2020-016369 ◽

Cited By ~ 2

Author(s):

Seyedeh Fatemeh Salimi Ashkezari ◽

Fernando Mut ◽

Bong Jae Chung ◽

Anne M Robertson ◽

Juan R Cebral

Keyword(s):

Intracranial Aneurysms ◽

High Speed ◽

Cerebral Aneurysms ◽

Vascular Reconstruction ◽

Flow Patterns ◽

Patient Specific ◽

Unstable Flow ◽

Geometric Characteristics ◽

Irregular Shapes ◽

Bleb Formation

BackgroundAlthough it is generally believed that blebs represent weaker spots in the walls of intracranial aneurysms (IAs), it is largely unknown which aneurysm characteristics favor their development.ObjectiveTo investigate possible associations between aneurysm hemodynamic and geometric characteristics and the development of blebs in intracranial aneurysms.MethodsA total of 270 IAs in 199 patients selected for surgical clipping were studied. Blebs were visually identified and interactively marked on patient-specific vascular models constructed from presurgical images. Blebs were then deleted from the vascular reconstruction to approximate the aneurysm before bleb formation. Computational fluid dynamics studies were performed in these models and in cases without blebs. Hemodynamic and geometric characteristics of aneurysms with and without blebs were compared.ResultsA total of 173 aneurysms had no blebs, while 97 aneurysms had a total of 122 blebs. Aneurysms favoring bleb formation had stronger (p<0.0001) and more concentrated inflow jets (p<0.0001), higher flow velocity (p=0.0061), more complex (p<0.0001) and unstable (p=0.0157) flow patterns, larger maximum wall shear stress (WSS; p<0.0001), more concentrated (p=0.0005) and oscillatory (p=0.0004) WSS distribution, and a more heterogeneous WSS field (p<0.0001), than aneurysms without blebs. They were also larger (p<0.0001), more elongated (p<0.0001), had wider necks (p=0.0002), and more distorted and irregular shapes (p<0.0001).ConclusionsStrong and concentrated inflow jets, high-speed, complex, and unstable flow patterns, and concentrated, oscillatory, and heterogeneous WSS patterns favor the formation of blebs in IAs. Blebs are more likely to form in large, elongated, and irregularly shaped aneurysms. These adverse characteristics could be considered signs of aneurysm instability when evaluating aneurysms for conservative observation or treatment.

Download Full-text

Comprehensive validation of computational fluid dynamics simulations of in-vivo blood flow in patient-specific cerebral aneurysms

Medical Physics ◽

10.1118/1.3675402 ◽

2012 ◽

Vol 39 (2) ◽

pp. 742-754 ◽

Cited By ~ 23

Author(s):

Qi Sun ◽

Alexandra Groth ◽

Til Aach

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Blood Flow ◽

Cerebral Aneurysms ◽

Patient Specific ◽

Computational Fluid Dynamics Simulations ◽

Dynamics Simulations

Download Full-text

Comparison Among Different High Porosity Stent Configurations: Hemodynamic Effects of Treatment in a Large Cerebral Aneurysm

Journal of Biomechanical Engineering ◽

10.1115/1.4026257 ◽

2014 ◽

Vol 136 (2) ◽

Cited By ~ 8

Author(s):

Breigh N. Roszelle ◽

Priya Nair ◽

L. Fernando Gonzalez ◽

M. Haithem Babiker ◽

Justin Ryan ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Simulation ◽

Cerebral Aneurysms ◽

Post Treatment ◽

Patient Specific ◽

High Porosity ◽

Velocity Magnitude ◽

Large Patient ◽

Aneurysm Model

Whether treated surgically or with endovascular techniques, large and giant cerebral aneurysms are particularly difficult to treat. Nevertheless, high porosity stents can be used to accomplish stent-assisted coiling and even standalone stent-based treatments that have been shown to improve the occlusion of such aneurysms. Further, stent assisted coiling can reduce the incidence of complications that sometimes result from embolic coiling (e.g., neck remnants and thromboembolism). However, in treating cerebral aneurysms at bifurcation termini, it remains unclear which configuration of high porosity stents will result in the most advantageous hemodynamic environment. The goal of this study was to compare how three different stent configurations affected fluid dynamics in a large patient-specific aneurysm model. Three common stent configurations were deployed into the model: a half-Y, a full-Y, and a crossbar configuration. Particle image velocimetry was used to examine post-treatment flow patterns and quantify root-mean-squared velocity magnitude (VRMS) within the aneurysmal sac. While each configuration did reduce VRMS within the aneurysm, the full-Y configuration resulted in the greatest reduction across all flow conditions (an average of 56% with respect to the untreated case). The experimental results agreed well with clinical follow up after treatment with the full-Y configuration; there was evidence of thrombosis within the sac from the stents alone before coil embolization was performed. A computational simulation of the full-Y configuration aligned well with the experimental and in vivo findings, indicating potential for clinically useful prediction of post-treatment hemodynamics. This study found that applying different stent configurations resulted in considerably different fluid dynamics in an anatomically accurate aneurysm model and that the full-Y configuration performed best. The study indicates that knowledge of how stent configurations will affect post-treatment hemodynamics could be important in interventional planning and demonstrates the capability for such planning based on novel computational tools.

Download Full-text

A Workflow for Patient-Individualized Virtual Angiogram Generation Based on CFD Simulation

Computational and Mathematical Methods in Medicine ◽

10.1155/2012/306765 ◽

2012 ◽

Vol 2012 ◽

pp. 1-24 ◽

Cited By ~ 14

Author(s):

Jürgen Endres ◽

Markus Kowarschik ◽

Thomas Redel ◽

Puneet Sharma ◽

Viorel Mihalef ◽

...

Keyword(s):

Fluid Dynamics ◽

Blood Flow ◽

Shear Stress ◽

Cfd Simulation ◽

Cerebral Aneurysms ◽

Patient Specific ◽

Hemodynamic Parameters ◽

Risk Of Rupture ◽

Computational Fluid Dynamics Cfd ◽

Subsequent Comparison

Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases.

Download Full-text