Extracting optical properties of turbid media using radially and spectrally resolved diffuse reflectance

摘要

Extraction of optical absorption and scattering coefficients from experimental measurements of spatially and/or spectrally resolved diffuse reflectance typically requires that measurements made on unknown samples be calibrated using those made on reference phantoms with well characterized optical properties. Here, we derive the optical scattering and absorption spectra of a solid homogenous resin-phantom using two analytical methods: radially resolved diffuse reflectance (RRDR) based fitting and spectrally resolved diffuse reflectance (SRDR) based fitting. Radially resolved data was acquired using a fabricated probe holder which connected one source fiber to 7 detector fibers with distances ranging between 1.65 to 12.5 mm. Each detector fiber was connected to a spectrometer and spectra ranging 450 to 800 nm were measured when a broadband halogen lamp was used as the source. Diffusion theory based, as well as scaled Monte Carlo based models were used to fit the spectrally and radially resolved reflectance (on a per wavelength basis) to derive the absorption and scattering spectra of the solid phantom. To assess the accuracy of these derived absorption and scattering properties, they were used as reference measurements to reconstruct the optical properties of liquid phantoms, with well-determined absorption and scattering. Reference optical properties determined using the SRDR methods were more accurate in reconstructing the optical properties in liquid phantoms. However, RRDR methods are useful to obtain a spectral profile of the absorption coefficient of an unknown media, for subsequent analyses using SRDR.