Extraction of optical properties from a turbid medium using fiber probe for spectral and spatial diffuse reflectance measurement

Abstract

Diffuse reflectance technique is popular in the study of tissue physiology through the change in optical properties in a noninvasive manner. Diffuse reflected light intensity is commonly collected either from a single distance with spectral measurement or from a single wavelength with different spatial distances. Improving existing systems is necessary in order to obtain information from greater depths and in smaller volumes. In this paper, we propose a fast and compact fiber probe-based diffuse reflectance method for combining the spectral measurements in the range of 400–950 nm and spatial information up to 1.33 mm from the illumination source. First, we chose the most appropriate analysis model for the proposed distances between the fiber probe and tested it on solid phantoms with varying scattering and absorption components. The measurements are compared to the scattering coefficients according to Mie theory and the absorption according to spectrophotometer measurements. Next, we measured two-layer phantoms with constant scattering and absorption contrast in different layer thicknesses. We extracted the penetration depth from the measured effective absorption coefficient. In the near-IR, we were able to detect the absorption coefficient of the bottom phantom layer behind a top layer of up to 5 mm. We achieved a maximum penetration depth of 5.7 mm for 5 mm top layer thickness at 900 nm. Our fiber probe diffuse reflectance system can be used in the near future for skin lesion detection in clinical studies.