Defining chromophore concentration of tissue phantoms by modeling spectroscopic data

This thesis describes a novel method for the analysis of back reflectance spectroscopic data to estimate concentration of endogenous or exogenous chromophors of tissue noninvasively and in real time. It has potential to be used in diagnosis of pathologic tissues based on the variation of biochemical composition of tissue and in treatment of photodynamic therapy to estimate concentration of photosensitizers.In this study, tissue phantoms have been prepared using intralipid and two different chromophors. In the first set of the experiments tissue phantoms were aqueous mixture of intralipid and methylen blue and in the second set of the experiments were aqueous mixture of indocyanine green (ICG) and intralipid. Variation of the intralipid and chromophors concentration in the tissue phantoms defined reduced scattering and absorption coefficients respectively. Reduced scattering and absorption coefficients ranges of the tissue phantoms were kept in the ranges of biological tissues. Spectroscopic measurements on the tissue phantoms were carried out using a miniature spectrometer, a backscattering probe consists of six illumination optical fibers and a single collection fiber, a halogen tungsten light source and a laptop. All the reflectance spectra were acquired by inserting tip of the probe nearly 1 mm into the tissue phantoms. Monte Carlo simulations of the experiments were performed and calculated. Total optical path lengths of the detected photons were used together with the experimental results to estimate concentration of the chromophors of the tissue phantoms.Outcomes of the study were estimating absorption and reduced scattering coefficients of tissue phantoms using single backreflection spectrum. In the ranges of the reduced scattering coefficients of 0.25- 1.1 mm-1 and absorption coefficients of 0.05-0.2 mm-1 scattering and absorption coefficients were estimated with an average error of 6.3 % and 11.4 % respectively.