SORS (Spatially Offset Raman Spectroscopy)

Deep Raman spectroscopy is a relatively recent development of Raman techniques including Spatially Offset Raman Spectroscopy (SORS) and its extreme case of transmission Raman spectroscopy. This group of techniques can look deeper inside the sample by collecting Raman photons with a bias towards deeper layers. The concept of deep Raman relies on the statistical nature of photon migration in scattering media. In SORS measurements, the excitation and collection zone on the sample surface are decoupled and the distance between them (offset) tends to correlate with the depth of Raman photon origin. Scattered photons originating from greater depths propagate further through the medium and spread apart due to Rayleigh scattering events before they re-emerge from the surface. By decoupling the excitation and collection area, the SORS technique can recover Raman photons from various depths within turbid media, in contrast to conventional confocal Raman spectroscopy that only measures up to a few hundred microns deep, depending on the optical properties of the sample.

In our lab we employ a highly adjustable SORS setup to specifically accommodate the needs of biological samples involved in various clinical applications. Through our ongoing collaboration with the the University Hospital of Ioannina (Prof. Seretis), we have demonstrated that SORS is a promising approach allowing to look deeper inside the skin tissue and collect Raman photons with a bias towards the bottom layer of the epidermis where certain types of skin cancer initially spread.

 

[1] Vardaki, Martha Z., et al. "Assessment of Skin Deep Layer Biochemical Profile Using Spatially Offset Raman Spectroscopy." Applied Sciences 11.20 (2021): 9498.

Published on  January 28th, 2022