Page 87 - Computational Modeling in Biomedical Engineering and Medical Physics

Computational domains 75

several errors. If the model will serve as a precise 3D CAD figure of the reconstructed
organ and tissue, the anatomical details become important, for example, the shape and
volume of a preoperatory and a postoperatory tumor. In such cases, where no meshing
process is needed and a high level of morphology detail is targeted, the important fea-
tures should no longer be removed.

Rigid and elastic arterial networks
In the medical and clinical engineering fields, the interest in the concept and develop-
ment of numerical models used as powerful and trustworthy tools for the investigation
of the arterial hemodynamics is rapidly increasing. These models can help us under-
stand the influence that different arterial networks, from physiologically normal to
aneurysm affected or stenosed blood vessels, from our circulatory system manifest
upon the transport of nutrients, oxygen, or substances with pharmacoclinical purpose,
for example, medication used in chemotherapy or magnetic drug targeting procedures.
Due to the human circulatory system complexity and individualities, the image-
based reconstruction for generating anatomically accurate computational domains
seems to be a promising virtualization method. The models described in this chapter
bear the significant advantage of representing the real morphology of the source (origi-
nal) blood vessels used in the segmentation process.
The first set of models simplifies the study of hemodynamic problems, considering
that the blood vessel walls are rigid. When advancing in age, the blood vessels tend to
lose their elastic properties and begin an atherosclerotic, calcifying process (Sangiorgi
et al., 1998). This assumption eliminates the flow structural interaction generated by the
pulsatile arterial blood flow. More complex models with elastic blood vessel walls, which
allow the study of blood pulsation vessel walls embedding tissue, are also described here.
Cardiovascular disease represents the main death cause in the modern world. For
example, atherosclerosis, which mostly affects elderly people, is responsible for the ves-
sel walls stiffening due to the cholesterol deposits (Pyörälä et al., 1994). The atheroma
plaque rupture can trigger myocardial or brain ischemia, causing myocardial infarction
or cerebrovascular accident (Zaman et al., 2000).
The blood vessel dimensions are well fitted to the blood flow stream and to the
viscous stress exerted upon the vascular endothelium (Davies, 1995). The morphology
of the arteries, geometry, and bifurcation regions is one of the most influential factors
in determining the blood flow, the wall viscous stress, and the mechanical forces that
play a key role in the atherogenesis process (Khanafer and Vafai, 2008), which is also
governed by the atherogenic macromolecules and the mass transport that occurs at the
arterial walls, from the blood stream to the surrounding tissues.
Considerable effort is being made to study and understand the hemodynamic flow and
the associated mass and heat transfer processes. The arterial hemodynamics is strongly