2011 - Europe Direct Iasi

EUROINVENT 2011
4.50.
A new method for calculation acceleration in medical
Title
applications of diffuse optical tomography
Authors Tomasz GRZYWACZ, Jan SIKORA
Electrotechnical Institute, Department of Electric
Institution
Traction, Warsaw, Poland
Patent no. Pending
DOT is an imaging modality with the aim to recover the spatial
distribution of the optical parameters, such as absorption and
scattering coefficients, and to present them as 3-D images to the
clinician. The optical parameters are related to physiologically
relevant properties of blood and tissue oxygenation levels.
The use of near-infrared light for imaging is quite difficult since
it is strongly scattered by tissue, unlike the radiation in CT,
which generally travels in straight lines through the body.
Diffuse light propagation complicates image reconstruction.
Light travelling between two points on the surface spreads out
over a significant volume inside the tissue and therefore carries
very little spatial information. To maximise the information
contained in the measurements, one uses multiple detectors to
sample the light emerging over a large surface area from the
body for each source.
DOT problem is highly nonlinear, and analytical solutions exist
only for a limited number of simple geometries. Previous
Description numerical solutions of the forward problem in DOT were based
on a finite element method (FEM) as well as various hybrid
approaches combining FEM with stochastic methods. Our
proposal is to combine BEM with domain decomposition
methods in order to solve this problem. This two methods are
complementary. The system of equations derived from BEM
describes distribution of the state function over a particular area.
BEM provides not only potential of the state function but also its
normal derivative in each node of the area. This property makes
BEM really convenient to cooperate with domain decomposition
methods. They are based on transfering boundary conditions
(Dirichlet, Neumann or mixed) between successive regions of
the decomposed area. Authors applied algorithms from two main
groups of domain decomposition methods: overlapping and nonoverlapping
ones. A diffusion approximation of the light
propagation model based on Helmholtz equation was solved in
spherical geometry. The results show significant reduction in
computation time while solving forward problem in DOT but
only for huge problems.
Class 4
85