Biomedical Engineering Reference
In-Depth Information
Fig. 8.33
Three-dimensional isometric view of the plaque in a carotid bifurcation. The plaque-
arterial configuration can be (
a
) non-calcified plaque, (
b
) mixed type of plaque and (
c
) calcified
plaque. Here, the lipid height and width is specified as 6.714 mm and 3.298 mm respectively, with
the fibrous cap at 0.500 mm thick
For a diseased carotid bifurcation, the plaque location is located on the outer wall
of the internal carotid artery (ICA) sinus in order to study the stenosis effect on the
flow as well as the mechanical stress occurs. A three-dimensional crescent structure
was incorporated into the sinus of the carotid bifurcation to simulate the presence of
plaque. The plaques can be characterized into three types based on the component
with it: non-calcified plaque, partially and fully calcified plaque (see Figs.
8.33a
-
c
respectively). Fibrous tissue (
α
), lipid (
β
) and calcium (
γ
) pertain to the homog-
enous calcification agglomerate at
α
= 5 %,
β
= 20 % and
γ
= 75 % as components for
a homogenous calcification agglomerate.
An anisotropic modelling of the atherosclerotic vessel was used to investigate
plaque vulnerability. A three-dimensional modelling platform for calibrating the
extent of plaque rupture was used based on mechanical parameters governing the
atherosclerotic configuration. Studies of plaque mechanics of arterial wall bending
along the longitudinal axis has shown that repetitive bending causes strain on an
atherosclerotic plaque resulting in rupture (Beaussier et al. 2008).
Figure
8.34
shows the computational mesh for a calcified carotid bifurcation
where a refined mesh is required for the calcified region. The mesh consisted of
three-dimensional tetrahedral and prism cells. Grid independence was performed
at 3 different mesh refinement levels for the structure domain: coarse (130,000 ele-
ments), medium (340,000 elements) and fine (1,500,000 elements). For the fluid
domain, the mesh refinement levels were: coarse (110,000 elements), medium
(300,000 elements) and fine (1,000,000 elements). For both the structure and fluid
domain, only 2 % of dissimilitude between the fine and medium mesh was observed.
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