In vitro and in vivo image and optical property reconstruction from noninvasive measurements of turbid media: A promising method for optical mammography
Walker, Scott Andrew
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https://hdl.handle.net/2142/31244
Description
Title
In vitro and in vivo image and optical property reconstruction from noninvasive measurements of turbid media: A promising method for optical mammography
Author(s)
Walker, Scott Andrew
Issue Date
1999
Doctoral Committee Chair(s)
Gratton, E.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
near infrared photons
diffusion model
optical inhomogeneities
Language
en
Abstract
Due to their multiple scattering, near infrared photons diffuse in human tissues providing interesting physiological information over relatively large volumes. By employing frequency-domain techniques along with a diffusion model for photon transport, one can separate contributions to light attenuation from absorption and scattering processes. Both the absorption and reduced scattering parameters are sensitive to physiological characteristics of tissues. I have employed the diffusion model, which assumes that tissue is homogeneous, to create an efficient reconstruction routine based on the back-projection technique to detect and locate inhomogeneities qualitatively.
Before my work in this field, researchers were uncertain whether the diffusion
model would be valid for a medium containing inhomogeneities. I, along with a handful
of other researchers demonstrated that the diffusion model is accurate enough to include
well behaved heterogeneous tissue models in which a number of macroscopic objects of
different size and shape are embedded in a homogeneous background medium. I have
employed a fitting of the experimental data to the diffusion model to accurately
reconstruct not only the position and size, but also the optical properties including the
relative index of refraction, absorption and scattering coefficients of objects immersed in highly scattering media. In this thesis I describe a model for locating and characterizing optical inhomogeneities in a turbid medium. I will go on to discuss limits of the technique and present data collected in vivo from a 55 year old female subject with a malignant breast cancer that was detected and optically characterized by these techniques.
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