Angular Distribution of Diffuse Reflectance in Biological Tissue

doi:10.1364/AO.46.006552We measured angular-resolved diffuse reflectance in tissue samples of different anisotropic characteristics. Experimental measurements were compared with theoretical results based on the diffusion approximation. The results indicated that the angular distribution in isotropic tissue was the same as in isotropic phantoms. Under normal incidence, the measured angular profiles of diffuse reflectance approached the Lambertian distribution when the evaluation location was far away from the incident point. The skewed angular profiles observed under oblique incidence could be explained using the diffuse model. The anisotropic tissue structures in muscle showed clear effects on the measurements especially at locations close to the light incidence. However, when measuring across the muscle fiber orientations, the results were in good agreement with those obtained in isotropic samples.This project was supported in part by National Science Foundation grant CBET-0643190, and the National Research Initiative of the USDA Cooperative State Research, Education, and Extension Service under grant 2006-35503-17619