Growth and Remodeling of Human Abdominal Aorta Aneurysms
Abstract: The human
abdominal aorta aneurysm (AAA) has been increasingly modeled as a continuous deformation
process in recent years. Changes in both structure and material of artery wall have been
studied and analyzed. This thesis aims to address key issues related to the nonlinear
modeling of AAA development, and a continuous growth and remodeling (G&R) model was
proposed. The model incorpo... read morerates artery wall material growth and degradation,
microstructure remodeling and artery vessel stability to simulate and predict the
aneurysm development. The kinematic model is described in which simultaneously occurring
growth and deformation are considered as a sequence of two mappings, one representing
stress-free growth and the other representing the deformations of the tissue due to
stresses acting on the tissue. In the simulation, we combine the growth theory and
remodeling theory, and apply it to the simulation of patient aneurysm development. Both
microstructure geometry and component mass changes are accounted for. The fundamental
concepts of the nonlinear theory of elasticity are addressed and suitable continuous
material models are formulated. The model depicts the changes of the outer radius of a
dilating abdominal aorta as a function of axial position over a twelve-year period with
an applied pressure of 16 kPa (120 mmHg). Numerical results show that over this period,
the maximum dilation increased from 12.94 mm to about 35 mm, and the elastin dropped
from 60% to less than 20%. From years 8 to 12, as the bulge expanded, the maximum von
Mises stress increased almost four times, from 235 to 925 kPa. Mixture theory of growth
and remodeling predicted the development of inhomogeneous mechanical properties and
dilatation of the diseased section of the arterial wall. The rate of expansion depended
primarily on the rate of production and removal of elastin and collagen as well as on
the change in fiber microstructure.
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Civil Engineering.
Advisor: Luis Dorfmann.
Committee: Helen Suh, Robert Viesca, James Adler, and Robert Peattie.
Keyword: Biomechanics.read less