Applications of FSI for Cardiovascular Haemodynamics - Computational Hemodynamics: Theory, Modelling and Applications - page 272

models based on the variation of d fc and E lp was performed to characterize critical
stress and maximum deformation levels. The sensitivity of the mechanical stress
properties to the lipid core elasticity and fibrous cap thickness are presented with
response curves that provide the interaction between different mechanical proper-
ties of the plaque material. This can give us insight into the morphological effect of
plaque constituents on maximum stress levels.
Figures 8.36c and d are simulated models with a constant lipid cores whose
Young's modulus is set as E lp = 1 kPa and a calcification agglomerate that has
Young's modulus E cag based on α = 5 %, β = 20 % and γ = 75 %. The changes in these
mechanical properties are shown when calcium clusters are present. Variation of
calcification gap d cg is presented to show its effect on peak principal stress and
maximum deformation. Modelling calcified plaque with agglomerate at varying
calcification gaps gives the response of maximum principal stress and deformation
based on the influence of calcium clusters. This mechanical entity affects structural
integrity of the overall plaque content, and plays a major role in plaque vulnerabil-
ity.

8.5.4 Three-Dimensional Fluid-Structure Interaction Modelling

8.5.4.1 Blood-Vessel-Plaque Modelling

Figure 8.37 are simulated three-dimensional models with constant lipid cores at
E lp = 1 kPa and a calcification agglomerate where E cag is based on α = 5 %, β = 20 %
and γ = 75 % (refer to Table 8.4 ). We extract the maximum principal stress and de-
formation contour plots for the carotid bifurcation along its longitudinal axis as it
is more easily visible to observe these mechanical property variations along the
fibrous cap. The results are based on a constant lipid pool ( E lp = 1 kPa) of fixed size
(0.35 mm), with a specific fibrous cap thickness d fc and calcification gap d cg .
The three-dimensional plaque models at 90 % stenosis under the effect of dif-
ferent fibrous cap configurations are illustrated by Figs. 8.37a and b . The different
plaque models with lipid cores of fixed size is effected and the influence of fibrous
cap thickness d fc on maximum principle stress and deformation is demonstrated to
be similar to the trend shown by the two-dimensional structural analysis, whereby
increment in the fibrous cap thickness d fc results in a reduction of critical stress and
maximum deformation.
Figures 8.37c and d are simulated blood-plaque-vessel models in which variation
of calcification gap d cg is presented to show its effect on peak principal stress and
maximum deformation. Here, increment of d cg results in an increase of these two
mechanical properties.

8.5.4.2 Plaque Elasticity and Structural Variation

Response curves for stress and deformation versus plaque composite elasticity and
fibrous cap thickness are plotted for the 2D (Fig. 8.38 ) and 3D models (Fig. 8.39 ).