Abstract

Intracranial aneurysm, a localized dilation of arterial blood vessels in the Circle of Willis and its branches, is potentially life threatening, due to massive bleeding in the subarachnoid space upon rupture. In clinical practice, one minimally invasive surgical procedure is the implantation of a metallic stent to cover the aneurysm neck. This flow diverting device can reduce the flow into the aneurysm and enhance the prospect of thrombosis, a condition expected to reduce the risk of growth and rupture. The biomechanical and haemodynamic factors in stented and nonstented situations are studied by computational fluid dynamics. Unlike earlier models with straight or curved parent blood vessels, the aneurysm is now located near an arterial bifurcation. The influence of the aspect (depth to neck) ratio of the aneurysm on the flow dynamics will be emphasized, especially in the post-operation stages. More precisely, the maximum flow velocity, the variations of wall shear stress, the risk of stent migration and volumetric flow rate after endovascular treatment will be studied. Aneurysms with larger aspect ratios (i.e. smaller neck sizes for constant depth) generally pose a greater risk in terms of these flow parameters. These results will assist the applications and design of stents in future neurosurgical therapy. The approach is limited to a nonelastic model, without taking into account of questions like stent expansion and interaction with tissue.

Highlights

  • INTRODUCTIONAt the base of the brain is a serious cerebrovascular disorder [1], occurring in roughly 2% to 5% of the population [2,3]

  • The formation of an intracranial aneurysm in the arteries at the base of the brain is a serious cerebrovascular disorder [1], occurring in roughly 2% to 5% of the population [2,3]

  • While these and earlier studies generally focused mainly on haemodynamic properties and aneurysm geometries, this paper addresses the potential risks of post-stenting aneurysm rupture and stent migration problems as well

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Summary

INTRODUCTION

At the base of the brain is a serious cerebrovascular disorder [1], occurring in roughly 2% to 5% of the population [2,3]. Intracranial aneurysms are usually saccular in shape Mechanisms for their formation and growth are still controversial, but haemodynamic and biomechanical factors are believed to play a crucial role [9,10,11]. Computational fluid dynamics has been utilized extensively to assess endovascular treatment quantitatively Both idealized models, i.e. those with a straight or curved parent artery, and patient specific cases have been employed. The magnitude of the shear forces acting on the stent tangentially in the post-operative stage will depend on the dimensions of the aneurysm necks (aspect ratio). Computational fluid dynamics (CFD) analysis (Section 2) [28,29] is conducted 1) to compare the nonstented (preoperative) and stented (post-operative) configurations, and 2) to measure the effectiveness of endovascular intervention by examining flow parameters (Section 3).

Software
Geometric Configuration
Fluid Properties
Governing Equations
Spatial Grid Sizes
Boundary Conditions
RESULTS AND DISCUSSIONS
Velocities and Pressure
Wall Shear Stress
Stent Migration
Volume Flow Rates
CONCLUSIONS
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