ARTICLE:

• A NEW SOLUTION METHOD FOR OPTICAL TOMOGRAPHY IN THE FREQUENCY DOMAIN  download article

H. K. Kim
Université du Québec à Chicoutimi, Chicoutimi, Canada

Andre Charette
Research Group in Processes and Systems Engineering, Université du Québec à Chicoutimi, Québec, Canada

ABSTRACT

As new reconstruction techniques, the sensitivity function-based conjugate gradient Method (SFCGM) and the conjugate gradient method without line search (CGMWLS) are described. A highly scattering, absorbing, non-reflecting, non-emitting medium is considered here and simultaneous reconstructions of absorption and scattering coefficients inside the test medium are achieved with the proposed optimization techniques, by using the exit intensity measured at boundary surfaces. The forward problem is solved with a finite-difference discrete-ordinates method on the framework of the frequency-domain full equation of radiative transfer. Four sources are placed at mid-center of the boundary surfaces and 80 detectors are used around the medium. The sources are intensity-modulated with the frequency of 600 MHz and the synthetic frequency-domain data are used as the input data. The effects of measurement error and different initial guesses on the image accuracy are investigated for the two methods. As a result, both the SFCGM and the CGMWLS can retrieve simultaneously the spatial distributions of optical properties inside the medium within a reasonable accuracy. Also it is found that the latter method outperforms the former in both the computation time and the robustness when it comes to convergence rate and stability to measurement error and initial guess.

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