Spatial Localization and Temporal Analysis of Optical Property Fluctuations by Multiplexed Near -Infrared Photon Density Waves in Turbid Media: In Vitro and in Vivo Studies
Filiaci, Mattia Emidio
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https://hdl.handle.net/2142/80464
Description
Title
Spatial Localization and Temporal Analysis of Optical Property Fluctuations by Multiplexed Near -Infrared Photon Density Waves in Turbid Media: In Vitro and in Vivo Studies
Author(s)
Filiaci, Mattia Emidio
Issue Date
2001
Doctoral Committee Chair(s)
Gratton, Enrico
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Optics
Language
eng
Abstract
Recently much attention has been given to the study of the processes in the human brain that lead to the changing of the optical parameters that characterize the tissue, measured by our frequency-domain instrumentation. These processes have been divided into two main categories with different time-scales. The slower one is mostly due to the fluctuations in the absorption coefficient caused by oxy- and deoxy-hemoglobin changes in the tissue. The temporal analysis of the signal resulting from this process is studied in detail, and I also introduce a time-series data analysis technique that has not been applied to this field before but was introduced in another area very recently. The faster time-scale process has been attributed to the electrochemical excitation of the individual neurons in the brain that have been observed to cause a change in the scattering coefficient of the tissue. This is the other primary parameter that is measured by our frequency domain instrument. However, before this work it has not been clear how to go about to better localize these smaller fluctuations. I present a novel idea for improving spatial localization of macroscopic optical parameter fluctuations, and study the characteristics of this optical probe design using analytical solutions to the diffusion equation and Monte Carlo simulations that more appropriately represent the volume of excitation of the cortex neurons.
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