Estimating the Reduced Scattering Coefficient of Turbid Media Using Spatially Offset Raman Spectroscopy

We propose a new method for estimating the reduced scattering coefficient, mu(s)', 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 mu(s)'-dependent, as such, permitting the determination of mu(s)'. The evaluation is carried out under the assumptions that absorption is negligible at the laser and Raman wavelengths and mu(s)' 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 mu(s)' coefficient of different turbid samples with an error (RMSEP) below 18%. The knowledge of mu(s)' 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.

Automated summary

The proposed method utilizes Spatially Offset Raman Spectroscopy (SORS) to estimate the reduced scattering coefficient (mu(s)') of turbid samples, with high accuracy achieved through calibration on a PTFE model sample. Knowledge of mu(s)' in the NIR range is valuable for optimizing SORS illumination and geometric configurations, providing in-depth information about SORS measurements, and benefiting various photon applications in fields such as biomedical, pharmaceutical, security, forensic, and cultural sciences.