| Biological tissues can be characterized by their optical properties, which include the scattering and absorption coefficients. The scattering depends on the microscopic morphological composition of the scattering centers (e.g. size and size distribution of the scattering particles), while the absorption depends on the biochemical composition of the tissue (e.g. blood volume fraction and oxygen saturation).;All organ surfaces have layered structures, such as the skin, colon and esophagus. The top layer, known as the epithelium, is where early signs of dysplasia occur and where carcinomas originate. Therefore, by monitoring changes in the optical properties of the epithelial layer, it is possible to non-invasively diagnose diseases at an early stage. This thesis is focused on developing a new method for diagnosing changes in the morphology and biochemistry of the epithelial layer, non-invasively and in real-time.;The method is based on spectral light reflectance, where a fiberoptic probe, in contact with the tissue of interest, is used to transmit light to and from the tissue. Monte Carlo simulations and experiments in tissue phantoms were used to empirically develop an analytical model that characterizes the reflectance spectrum in a turbid medium. The model extracts the optical properties (scattering and absorption coefficients) of the medium at small source-detector separations and at wavelengths where the absorption coefficient exceeds the scattering coefficient (e.g. hemoglobin Soret band), for which the diffusion approximation is not valid. The accuracies of the model and the inversion algorithm were investigated and validated.;The model was tested in vivo on patients with Inflammatory Bowel Disease yielding a high accuracy in classifying normal from inflamed tissues. Finally, the influence of the probe pressure on the local optical properties of the tissue was investigated as a source of variance. |
