Keywords: blood flow simulation, finite element method, computational fluid dynamics, Doppler ultrasound imaging.

The accumulation of plaques at the artery wall is a progressive disease facilitated by local irregular flow field. In recent years non-invasive medical imaging data acquisition made it feasible to construct three dimensional models of blood vessels [1]. Since the carotid arteries are superficial vessels, they are well suited for medical image acquisition using ultrasound to detect narrowing resulting from atherosclerotic stenosis. Furthermore, ultrasound is inexpensive, widely accessible, fast and safe.

The definition of high quality surfaces of blood vessels is crucial to guarantee correct numerical results of the blood flow simulations. In this paper a semi automatic methodology for patient-specific reconstruction and structured meshing of nearly-planar carotid bifurcation based on Doppler ultrasound images is presented. A three dimensional finite element model developed for the blood flow simulation of the carotid artery bifurcation [2] is considered where blood flow is described by the incompressible Navier-Stokes equations and the simulation is carried out under pulsatile conditions. The numerical procedure for the transient non-Newtonian equations uses the Galerkin-finite element method and a fractional-step method for the integration in time. At each time step Picard iteration is applied to linearize the non-linear convection and diffusion terms.

The proposed methodology represents a tool to analyse blood flow in vascular frameworks. The accuracy and efficiency of the model is validated comparing simulation results with experimental data collected during clinical practice. The example presented considers left carotid artery bifurcation data including blood flow velocities, as well as, flow waveforms that were obtained with ultrasound measurements. Three-dimensional geometry of the carotid arterial bifurcation is reconstructed from two-dimensional longitudinal images and complemented by a serial of two-dimensional transverse images. Simulated velocity fields and waveform along the cardiac cycle at the internal and external carotids using input measured data at the common carotid artery exhibit features very similar to the acquired data. The noninvasive nature of this approach makes it possible to consider studies in which the pre-atherosclerotic hemodynamic environment is compared with the post-disease state on a subject-specific basis.

1

C. Schumann, M. Neugebauer, R. Bade, B. Preim, H.O. Peitgen, "Implicit vessel surface reconstruction for visualization and CFD simulation", Int. J. Computer Assisted Radiology and Surgery, 2, 275-286, 2008.

2

L. Sousa, C. Castro, C. Antonio, R. Chaves, "Computational Techniques and Validation of Blood Flow Simulation", WSEAS Transactions on biology and biomedicine, 4-8, 145-155, 2011.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £50 +P&P)