Kivonat:
We aim to introduce a novel, inverse method for in vivo
material parameter identification of human abdominal aortic
aneurysms (AAA), which could overcome one of the greatest
sources of uncertainty in patient-specific simulations, and
could also serve as a rapid, patient-calibrated, novel
measure of aneurysm rupture risk. As an initial step, the
determination of the kinematic fields is presented here.
Images of the AAA lumen, acquired in 10 discrete time-steps
through a stabilized cardiac cycle by electrocardiogram-gated
computer tomography angiography, are used to approximate the
in vivo, time dependent kinematic fields of the arterial wall
using a novel, incompressible Kirchhoff–Love shell element
implemented into the isogeometric analysis framework.
Defining a smoothing parametric surface via 2D bicubic spline
fitting in the spatial, and by harmonic regression in the
temporal domain, we are able to adequately mitigate the
measurement inaccuracy. The ill-posedness of the problem
requires certain assumptions on the displacement. In our
case, based on numerical fluid structure interaction
simulation observations, we hypothesized the incremental
displacement vector of the reference surface to coincide with
its corrected normal; hence the periodic movement was
assured. Finally, we present two examples: an AAA and an
undilated calcificated aorta. Strains in the diseased part
were compared to those in a healthy arterial section of the
same patient and found to have significant differences in
both specimens. In the case of AAAs, high spatial gradients
surrounding the dilated part indicate abrupt changes in
material properties, a phenomenon less significant for the
atherosclerotic case.