In vivo Diffuse Reflectance Micro-Spectroscopy for correction of Raman depth profiles acquired on skin

摘要

Confocal Raman microspectroscopy is a relevant and useful tool to perform in vivo diagnosis of cutaneous tissues noninvasively and without labeling. This optical technique provides in-depth molecular and conformational characterization of skin. Unfortunately, spectral distortions occur due to elastic scattering. Our objective is to correct the attenuation of in-depth Raman peaks intensity by considering elastic scattering in biological tissues. In this purpose, a correction model was constructed using skin scattering properties as parameters thus enabling quantitative analysis. The work presented here is a technique of in vivo Diffuse Reflectance Micro-Spectroscopy called Micro-DRS. It achieves optical properties characterization in the skin layers probed by Raman microspectroscopy. The Micro-DRS setup can easily be coupled to a confocal Raman micro-probe to perform simultaneous measurements. Thanks to Monte Carlo simulations and experimental results obtained on homemade solid phantoms mimicking skin optical properties, we show that it is possible to measure the absorption coefficient μ_a, the reduced scattering coefficient μ_s', the scattering coefficient μ_s and the anisotropy of scattering g with this new apparatus. The measured scattering properties can be used subsequently as parameters in our correction model. Coupled to a Raman micro-spectrometer, Micro-DRS enables a quantitative analysis when tracking drug penetration through skin and it can be used independently to provide additional diagnosing criterions.