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VIGRE seminar, fall 2000: Soft Tissue Modeling
- Instructors
- Jay Walton, David Dobson
- Students enrolled
- Sherry O'Rourke (undergraduate bioengineering student); Michael
Flanagan, Amie Moch, Haewon Nam, Christopher Romero, Stephen
Shauger (graduate mathematics students); Kaibin Fu (graduate
aerospace student); Rudolph Gleason, Sungsod Na, Ruchi Singhal,
Katherine Smith, Paul Wells (graduate bioengineering students)
- Description
- A continuation of past VIGRE courses. The topic was soft tissue
modeling with two specific applications, the first being a
continuation of the arterial tissue modeling and the second
involving the lamina cribrosa, a soft plate like structure forming
part of the optical disk. The work on the lamina cribrosa was done
in collaboration with Theresa Good of the Chemical Engineering
Department, who is researching glaucoma.
In particular, it is not well understood why elevated interocular
pressure leads to the death of optical nerve cells since some
people with elevated pressure experience no vision loss while
others with normal interocular pressure suffer from glaucoma
symptoms. Based upon her work on mechanically induced death of
nerve cells, Good conjectured that deformation of the lamina
cribrosa holds the key to understanding the progression to clinical
symptoms. The idea is simple; Good showed in the lab that straining
axons to a sufficient degree initiates chemical processes within
the nerve cell leading to its death. Basically, nerve cells
self-destruct when their axons are strained too much. In the eye,
the axons from rods and cones in the retina pass out of the eye
through the lamina cribrosa forming the optical nerve network going
to the brain. The conjecture is that higher fluid pressure in the
eye causes the lamina cribrosa to bulge outward thereby straining
the axons passing through it to the point that they initiate the
self-destruct processes within their associated neuron. A key
element of verifying this conjecture is the ability to predict how
much bulging the lamina cribrosa undergoes with increased
interocular pressure. This is where the soft tissue modeling comes
in. The lamina cribrosa is known to be highly anisotropic due to a
dense matrix of oriented fibers forming its main structural
component.
The class was divided into a group pursuing the arterial modeling
and a group attempting to model the lamina cribrosa. The latter
group not only had to address of problem of modeling the
constitutive properties of the material, but also solve a
complicated boundary value problem that attempts to capture in situ
boundary conditions. In addition to the mathematics students, the
arteries group had students from Humphrey's research group and the
lamina cribrosa group had students from Good's research group. The
students seemed to benefit from the interdisciplinary interactions.
Each group had working models by the end of the semester.
- Impact
- Walton and Wilber (VIGRE-supported postdoc) completed their
first paper on nonlinear elasticity models relevant to soft tissue
which was started during past VIGRE courses on the same
subject.