Article
Development of an aneurysm model in order to improve computational flow dynamic analyses
Entwicklung eines Glasaneurysmamodells zur Verbesserung der computational flow dynamic analyses
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Published: | May 8, 2006 |
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Objective: Over the past years there is an increasing number of studies dealing with computational flow dynamic analyses (CFDA) in cerebral aneurysms published in the medical literature. Several forces e.g. shear forces and impact forces were calculated in order to evaluate the stress applied to the vessel wall. In order to evaluate these forces using a computational fluid analysis programme some physiological parameters like the viscosity of the blood or the elasticity of the vessel wall have to be chosen. In different publications different parameters were employed. Furthermore these computer programmes have been developed for engineering purposes and mostly not been evaluated in a biomedical setting. Aim of this study was to develop a simple glass model for direct simplified measurements of the flowdynamics in aneurysms.
Methods: A simple glass model with smooth angels was blown by an expert glass blower. A bifurcation aneurysm was chosen. The parent vessel ended in the aneurysm and the branches originated at an 90°angle. The model was designed so that the total area of the branches was approximately equal to the area of the parent tube so that neither acceleration nor deceleration would occur at the branch point. A modified Stehbens apparatus was used to perfuse the bifurcation. Essentially this consisted of a constant pressure reservoir filled from the taps, with the pressure kept constant by an overflow. This was connected by tygon tubing to the glass model and the outflow went via resistance to a stopcock and the sink. Evans blue dye was injected into the tygon proximal to the glass tube in order to study the flow profiles.
Results: The following flow profile could be observed. The axial stream flowed rapidly into the aneurysm sac with little deflection until it reached the apex. Then turbulences appeared within the aneurysm and the side branches. Some backflow appeared on the origin of the lower branch. Severe turbulences appeared in the parent trunk. These flow patterns were reproducible.
Conclusions: We present a simple glass model which offers the possibility of studying flow patterns in a simplified aneurysm. We know that this model does not reflect the clinical situation, but with further additions e.g. the use of pulsatile flow, and fluids mimicking blood viscosity evaluation of computer simulations and clinical situations seems possible.