Graduation Semester and Year

2008

Language

English

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Bioengineering

First Advisor

Georgios Alexandrakis

Abstract

Diffuse Optical Imaging (DOI) is being extensively used in brain activation studies for the quantification of hemodynamic changes in the cerebral cortex. Many investigators have utilized the commercially available CW5 DOI device to attain cortical activation maps. However, the localization and spatial resolution in the resulting activation images remains poor. These limitations arise due to the large source detector separations required for light to reach the brain's surface and the limited number of detector channels in the CW5 system, which result in sparse spatial sampling of the cortical activation regions. In this thesis we assess the feasibility of using denser optode geometries to improve the localization and spatial resolution of activation regions for the existing CW5 system. The CW5 response to brain activity is simulated using Monte Carlo for different sizes, locations of activation regions and optode arrangements. It was found that maximizing the number of detector channels that can be accommodated by the CW5 system results in an improvement in spatial resolution of about 20%. As it is not possible to know the exact optical properties of the brain tissue structures, we also investigated the possibility that spatial resolution of the reconstructed images is compromised by incorrect assumption of these background optical optical properties. It was found that the improved spatial resolution was robust to incorrect knowledge of the background tissue optical properties within their known physiological range of values. We conclude from these findings that the proposed detector geometries could improve image quality.

Disciplines

Biomedical Engineering and Bioengineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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