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by Tiziano Passerini
Italian scientific program Aneurisk (www2.mate.polimi.it:8080/aneurisk,
2005-2008) aims at evaluating the role of vascular geometry and hemodynamics
in the pathogenesis of cerebral aneurysms. Within this context, specific attention
has been devoted to Internal Carotid Artery (ICA), in order to assess
correlations between its morphological and fluid-mechanical features and the
presence and eventually the development or the rupture of aneurysms in cerebral
vasculature.
Starting from a classification of Aneurisk dataset of angio-CT images, based
on ICA geometrical characteristics, fluid dynamics computations are exploited
to find different mechanical behaviour of vessels belonging to different classes.
In particular the role of wall shear stress (WSS) is evaluated, as a possible responsible
for arterial wall tissue damage. Adding WSS to the set of considered
geometrical variables could improve the classification technique, and possibly
give information on the risk of pathology development associated to each class.
A central point in the study of cardiovascular fluid mechanics is the proper
description of systemic circulation: hemodynamics is studied in detail in specific
vascular districts, embedded in complex vascular networks. Geometrical
multiscale models are considered in order to reproduce the mechanical interaction
between pathological vessels and the whole cerebral circulation. The
cerebral vascular system is reproduced by a network of one-dimensional models,
based on Euler equations, describing the main cerebral arteries; peripheral
circulation is described by zero-dimensional models, while three dimensional
models based on the incompressible Navier-Stokes equations describe blood
flow dynamics in the domain of interest. A simplified fluid structure interaction
(FSI) model for arterial districts is considered, based on the assumption
that vessel compliance can be described by zero-dimensional models, gathered
at the inflow and outflow sections of three-dimensional rigid models. This
strategy allows to significantly reduce computational costs with respect to FSI
algorithms based on the coupling of a fluid solver and a structure solver.
All the computations (incompressible Navier-Stokes equations, Euler equations,
zero-dimensional and multiscale models, WSS evaluation) have been
carried out with softwares based on C++ finite element method library LifeV
(www.lifev.org), a project born from the collaboration of several european universities,
in which the author is currently involved as a developer. Preliminary
results will be discussed and future applications will be addressed.
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