Key result
Outflow boundary conditions drive carotid bifurcation CFD flow patterns more than vessel extensions.
Why the study?
Various ways to utilize flow data from three-dimensional ultrasound for CFD simulations of carotid bifurcation may lead to different flow and wall shear stress results, and the impact of vessel extensions and outflow conditions needs clarification.
In computational fluid dynamics simulations of carotid flow using 3D ultrasound data, outflow boundary conditions have a stronger influence on predicted flow patterns than artificial extensions of daughter vessels.
3D ultrasound enables patient-specific CFD for atherosclerosis; leaves open clinical adoption pending validation studies.
Computational fluid dynamics (CFD) flow simulation techniques have the potential to enhance understanding of how haemodynamic factors are involved in atherosclerosis. Recently, three-dimensional ultrasound has emerged as an alternative to other three-dimensional imaging techniques, such as magnetic resonance angiography (MRA). The method can be used to generate accurate vascular geometry suitable for CFD simulations and can be coupled with Doppler ultrasound to provide physiologically realistic flow boundary conditions. However, there are various ways to utilize the flow data acquired, possibly leading to different results regarding both flow and wall shear stress patterns. A disadvantage of three-dimensional ultrasound for imaging the carotid bifurcation has been established as being the scanning limitation of the jawbone position. This may make artificial extensions of the internal and/or external carotid arteries necessary, which in turn may influence the predicted flow patterns. Flow simulations were carried out for three outflow calculation schemes as well as four geometries with different extensions to the carotid daughter vessels. It was found that variation of flow patterns was more strongly influenced by the outflow conditions than by the extensions of the daughter vessels. Consequently, it is recommended that for future CFD simulations of carotid flow using three-dimensional ultrasound data, the outflow boundary conditions should rely on the most accurate measurement available, and flow data recorded in the common and internal carotid are considered more reliable than data from the external carotid. Even though the extended lengths of the daughter vessels have insignificant effects on the predicted haemodynamic parameters, it would be a safer option to extend the internal carotid by approximately three times the diameter of the common carotid artery.
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Augst et al. (2003) studied Carotid bifurcation flow / Atherosclerosis. Outflow calculation schemes and vessel extensions in CFD simulations was evaluated on Variation of flow patterns and wall shear stress. Variation of flow patterns in carotid bifurcation CFD simulations was more strongly influenced by outflow conditions than by artificial extensions of the daughter vessels.
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