Effect of flow diverting stents on intracranial artery bifurcations with a focus on bifurcating vessels diameter on hemodynamics and occlusion

Table of Contents

1 INTRODUCTION

1.1 Clinical Background/ Theory

1.2 Motivation

1.3 Hemodynamic variables

1.4 Computational Fluid Dynamics (CFD)

2 THESIS

2.1 Literature Review

2.2 Preliminary Work

2.2.1 Steady state analysis and Laminar flow

2.2.2 Geometry

2.2.3 Properties of Blood

2.2.4 Parabolic velocity profile

2.2.5 Rigid walls assumption

2.2.6 Mesh structure

2.2.7 Boundary conditions

2.3 Porosity model

2.4 Methodology

3 RESULTS

3.1 Unstented

3.1.1 Pressure

3.1.2 Wall Shear Stress

3.2 Stented

3.2.1 WSS Average 1

3.2.2 WSS Average 2

3.2.3 Pressure Inlet

3.2.4 Average Pressure 1

3.2.5 Average Pressure 2

3.3 Stented vs Unstented

3.3.1 Stent Small Artery (A2) vs Unstented

3.3.2 Stent Big Artery (A1) vs Unstented

4 Validation

4.1 Mesh independency

4.2 Wall Shear Stress

5 DISCUSSION

6 CONCLUSION

Research Objectives and Topics

The primary aim of this project is to investigate the effects of flow-diverting stents on intracranial artery bifurcations, specifically analyzing how the relative diameter of bifurcating vessels impacts hemodynamics and the potential risk of vessel occlusion. The research utilizes Computational Fluid Dynamics (CFD) to model these complex interactions and determine key variables that may assist clinicians in improving treatment outcomes and preventing ischemic complications.

• Analysis of hemodynamics in intracranial arterial bifurcations.
• Evaluation of the impact of bifurcating vessel diameter ratios on flow.
• Use of CFD and porous media modeling for stent simulation.
• Investigation of Wall Shear Stress (WSS) and pressure alterations.
• Comparison of stented versus unstented arterial geometries.

Excerpt from the Book

Summary of Chapters

1 INTRODUCTION: This chapter introduces the clinical relevance of intracranial aneurysms and the motivation for using Computational Fluid Dynamics to study hemodynamic effects of flow-diverting stents.

2 THESIS: This section details the methodology, including literature review, geometric modeling, blood properties, and the implementation of the porosity model to simulate stents.

3 RESULTS: This chapter presents the data obtained from simulations, comparing pressure and Wall Shear Stress distributions in unstented and stented models across various diameter ratios.

4 Validation: This section confirms the accuracy of the CFD simulations by performing a mesh independency study and comparing the results against theoretical Poiseuille flow calculations.

5 DISCUSSION: This chapter interprets the findings, linking hemodynamic alterations—specifically pressure gradients and shear stress—to the risk of arterial occlusion.

6 CONCLUSION: This chapter summarizes the project's achievements, noting that stent placement significantly alters hemodynamics and highlighting the need for further patient-specific research.

Keywords

Intracranial aneurysm, Flow diverting stents, Hemodynamics, Computational Fluid Dynamics, Wall Shear Stress, Vessel occlusion, Bifurcation, Arterial geometry, Murray’s law, Pressure gradient, Endothelial cells, Porosity model, Windkessel model, Ischemic complications, CFD simulation.

Frequently Asked Questions

What is the core subject of this research?

The research examines the hemodynamic impact of placing flow-diverting stents on intracranial artery bifurcations and how vessel diameter ratios influence the risk of arterial occlusion.

What are the primary fields of study?

The study integrates biomechanics, fluid dynamics, and clinical neurology to understand the vascular behavior and treatment risks associated with brain aneurysms.

What is the central research question?

The project asks how the placement of flow-diverting stents and the relative diameters of bifurcating vessels alter pressure and shear stress, and whether these changes contribute to vessel occlusion.

Which scientific method is utilized in this work?

The researcher uses Computational Fluid Dynamics (CFD), specifically ANSYS-CFX 15.0, to model fluid behavior, using a porous medium to represent the stent structure.

What does the main body cover?

The main body covers the theoretical background, the setup of idealized arterial geometries, mesh generation, boundary conditions, and a comparative result analysis between stented and unstented models.

Which keywords define the research?

Key terms include Hemodynamics, Intracranial Aneurysms, Flow Diverting Stents, CFD, Wall Shear Stress, and Bifurcation mechanics.

How does the Windkessel model assist in the study?

The Windkessel model is used to simulate the peripheral resistance of the arterial system at the outlets, allowing for a realistic distribution of flow and pressure across the bifurcating vessels.

Why are endothelial cells relevant to these results?

Endothelial cells are highly sensitive to Wall Shear Stress (WSS); the study speculates that altered WSS after stenting can trigger destructive remodeling, which may lead to vessel occlusion.

How does Murray's law relate to the experiment?

Murray's law provides the theoretical basis for selecting the range of bifurcating artery diameters used in the simulations to ensure the modeled geometries are physiologically relevant.