Estimating the Reduced Scattering Coefficient of Turbid Media Using Spatially Offset Raman Spectroscopy.
Mosca S., Dey P., Salimi M., Gardner B., Palombo F., Stone N., Matousek P.
We propose a new method for estimating the reduced scattering coefficient, μs', of turbid homogeneous samples using Spatially Offset Raman Spectroscopy (SORS). The concept is based around the variation of Raman signal with SORS spatial offset that is strongly μs'-dependent, as such, permitting the determination of μs'. The evaluation is carried out under the assumptions that absorption is negligible at the laser and Raman wavelengths and μs' is approximately the same for those two wavelengths. These conditions are often satisfied for samples analyzed in the NIR region of the spectrum where SORS is traditionally deployed. Through a calibration procedure on a PTFE model sample, it was possible to estimate the μs' coefficient of different turbid samples with an error (RMSEP) below 18%. The knowledge of μs' in the NIR range is highly valuable for facilitating accurate numerical simulations to optimize illumination and collection geometries in SORS, to derive in-depth information about the properties of SORS measurements or in other photon applications, dependent on photon propagation in turbid media with general impact across fields such as biomedical, pharmaceutical, security, forensic, and cultural sciences.