Date of Award

Fall 2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

Ravindra P. Joshi

Committee Member

Frederic D. McKenzie

Committee Member

Linda Vahala

Call Number for Print

Special Collections LD4331.E55 C47 2009

Abstract

Lasers, due to their unique properties, have a wide range of applications in the medical field. For accurate laser treatments that focus on bio-tissues, prior knowledge of the amount of laser power, spot size and its irradiation time are necessary. In order to predict the effects of lasers on tissues and their bio-effects, a first necessary step is the creation of a model that can predict the temperature distributions within the tissue following laser excitation. This involves modeling light propagation through the tissue with inclusion of internal scattering, and assessment of the energy deposited by the incoming photons. The next step is the thermal diffusion of this deposited energy leading to heat production and temperature increases within the surrounding tissue.

A three-dimensional, computer-based Monte Carlo model was developed to simulate laser tissue interactions and study the effects of laser heating of bio-tissues. In this model photons were treated as a stream of neutral particles having discrete energies. This numerical approach has been used for calculating the energy deposition by the incident laser onto a heterogeneous tissue as a function of depth. Next, the heat re-distribution and corresponding changes in tissue temperature were evaluated based on the Pennes bioheat transfer equation. Suitable results and discussions of energy deposition and time dependent temperature changes in multi-layered tissue are presented in this thesis.

Finally, for completeness, numerical implementations for including the wave-particle duality of light were discussed. The intent was to understand the effects of phase changes and include the phase information in laser photons propagation within the bio-material. A two dimensional Monte Carlo simulation model based on Huygens Fresnel principle was developed to present the effects of phase changes, and provide quantitative predictions of the laser's energy and intensity.

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DOI

10.25777/72mf-mk75

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