Biomedical Engineering Reference
In-Depth Information
Discussion
Using representative constitutive equations and material parameters cerebral angio-
plasty was modelled using an acute damage model. Large tissue damage and an
increase in unloaded vessel diameter modelled demonstrated. Further investigation
is needed to assess the modelling idealizations. Currently, we use a rigid walled
balloon controlled by displacement loads. For simplicity, we have not included ar-
terial plaque. For some applications, this idealization may also need to be relaxed.
The current model does not incorporate arterial residual stresses, which may change
wall stress distributions. Further we have only considered the passive behaviour of
arteries. The contribution of smooth muscle cells will have to be included to study
the active response of arterial tissues.
To further verify and refine the current constitutive model, in-vitro and in-vivo
studies are in great needed. For example, additional experimental data for the layer-
specific responses of cerebral arteries are needed. The inelastic response of the IEL
and media must be investigated to develop the functional forms of the damage crite-
ria. Experimental data are also required for a quantitative validation of the compu-
tational results, especially the relationship between loading and residual stretch fol-
lowing PTA. Due to the large number of material parameters utilized in the model,
a detailed sensitivity analysis should be carried out in future studies.
We also recognize that in some vessels, the assumption of isotropy many not be
appropriate. For example, Holzapfel et al. [56] analyzed the mechanical properties
of nonstenotic human coronary arteries with intimal thickening and found the intima
to be the stiffest wall layer and to display. The intima layer was highly anisotropic
with increased stiffness in the longitudinal direction. They conjectured that since this
stiffness was seen for larger loads, it is likely due to orientation to collagen fibres.
For the long lasting effects of PTA, tissue mechanobiology including degeneration,
repair, growth and remodelling will be important features to be modelled.
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