Visualisering av funktionell och morfologisk hjärt-kärl-diagnostik

Simulation of arterial flows
with
Clinical relevance
Laszlo Fuchs, Mechanics, KTH
Background:
Cardio-vascular diseases cause about 50% of mortalities in Western countries. Most of cardiovascular
events are related to atherosclerosis and associated problems. Arterial lesions are focal in
character (near branches and bends in larger arteries) and therefore cannot be explained only in
terms chemical-immunological processes if the blood composition is assumed to be homogenous.
Our research addresses some basic questions related to pulsatile blood flows in larger arteries and in
particular in branches.
Goals:
The projects are aimed both at basic understanding of the flow itself, the interaction between the
flow and the blood and the effects of the flow on the arterial walls. Additionally, we apply the basic
understanding to problems of clinical interest.
Understanding of the fluid mechanical contribution to atherosclerosis has been a topic of research
over long time. It is believed that the flow itself only cannot explain the very slow and multifacetted
process of atherosclerosis. Our hypothesis is the flow affects not only the stresses on the
walls of the arteries but also the composition of the blood (cells and solvents) locally, whereby the
process becomes localized. Local blood composition changes also the rheology of the blood which
results in modification of the flow itself. This impact of this non-linear interaction is unknown.
Potential clinical applications:
The forces acting on the walls of the arteries and the physiological response to the temporarily and
spatially varying stresses may also lead to aneurysm. The flow is also affected by the particular type
of arterial reconstruction. Understanding these aspects can lead to patient specific arterial (and
bypass) surgery. Similarly, blood flow in extracorporeal systems (e.g. heart-lung machines,
hemodialysis) can be improved and/or reducing hazard by utilizing the gained knowledge.
Methods and models:
We use computational and experimental tools for studying the flow, mixing and vessel-flow
interaction in relevant geometries. We are developing models for blood rheology based on the local
red-blood-cell and macro-molecule concentration. We also develop models for describing the local
distribution of solvents with different diffusivities (depending on molecule size). The forces acting
on the walls and the resulting deformation of the vessel is also included in the modelling research.
The experimental work includes measuring the flow (time-resolved local velocity vector), and local
concentrations of substances with different molecular diffusivities. All measurements are done
using non-intrusive methods. We measure the velocity using Laser Doppler Velocimetry (LDV) or
Particle Image Velocimetry (PIV). These methods are more accurate than ultra-sound based
technique which is more suitable for optically opaque cases. Concentration of solvents is measured
simultaneously with the velocity using Laser Induced Fluorescence (LIF) utilizing multiple lasers.