Elastography is an emerging functional imaging technique of current
clinical research interest due to a direct relation between
mechanical material parameters, especially the tissue stiffness, and
tissue pathologies such as cancer. Digital Image Elasto-Tomography
(DIET) is a new method that aims to develop elastographic techniques
and create a simplified, improved breast cancer screening process.
The elastic material information of breast tissue is reconstructed
in the DIET concept from mechanically excited steady-state harmonic
motion observed on the surface of the breast. While this inversion
process has been traditionally approached using finite element
methods, this surface-orientated problem is naturally suited to the
use of Boundary Element Methods (BEMs) requiring the discretization
only on the surface of the domain and on the interface of a
potential inclusion. As only approximate information is available
about breast tissue material parameters, this thesis presents the
development of BEM based inverse problem algorithms suitable for the
reconstruction of all material parameters in a proportionally damped
isotropic linear elastic solid, where only the material density is
known. The highly nonlinear identification process of a potential
inclusion is treated through the combination of a systematic
Grid-Search with gradient descent techniques. This algorithm is
extended to a three-step algorithm that performs a background
material parameter estimation before the subsequent identification
of an inclusion and thus provides a confident indication for the
differentiation between cancerous and healthy breast tissue. The
development of these algorithms is illustrated by several simulation
studies highlighting important reconstruction behaviors relevant to
the elastographic inverse problem. A first experimental test on a
silicon based breast phantom is presented.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/4413 |
| Date | January 2009 |
| Creators | Berger, Hans-Uwe |
| Publisher | University of Canterbury. Mechanical Engineering |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Hans-Uwe Berger, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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