Diffuse reflectance spectroscopy of human colon tissue

Abstract

Diffuse reflectance spectroscopy can provide quantitative biochemical and morphological information for the analysis of biological tissue epithelium and the detection of precancerous lesions. To investigate this, diffuse reflectance spectra were collected from adenomatous colon polyps (cancer precursors) and normal colonic tissue of patients undergoing colonoscopy. To analyze the data, an analytical model was developed based on the diffusion of light in tissue. The model was formulated in terms of the absorption and scattering properties of tissue. In the case of absorption, hemoglobin was identified as the major absorber of light, and scattering was modeled as a homogeneous of collection spherical microparticles using Mie scattering theory. The validity and accuracy of the analytical model was tested and validated on a physical tissue model (phantom) composed of polystyrene beads and hemoglobin and it was found that it is suitable for application to the tissue data. Four parameters were obtained by analyzing the tissue data using the model: hemoglobin concentration, hemoglobin oxygen saturation, effective scatterer density and size. Normal and adenoma tissue sites exhibited differences in hemoglobin concentration and effective scatterer size, in agreement with other studies which employ standard methods. These results demonstrate that diffuse reflectance can be used to obtain tissue biochemical and morphological information in vivo.