Noninvasive Raman Spectroscopy of Human Tissue in vivo

Abstract

We report the first transcutaneous Raman spectrum of human bone in vivo obtained at skin-safe laser illumination levels. The spectrum of thumb distal phalanx was obtained using spatially offset Raman spectroscopy (SORS), which provides chemically specific information on deep layers of human tissue, well beyond the reach of existing comparative approaches. The spectroscopy is based on collecting Raman spectra away from the point of laser illumination using concentric rings of optical fibers. As a generic analytical tool this approach paves the way for a range of uses including disease diagnosis, noninvasive probing of pharmaceutical products, biofilms, catalysts, paints, and in dermatological applications.

Decomposition of in vivo spatially offset Raman spectroscopy data using multivariate analysis techniques

“…[10] Technologies that enable the retrieval of accurate Raman spectra of bone through the skin (and other overlaying tissues) thus have the potential to improve the diagnosis of bone disease SORS has been used to retrieve Raman spectra of bone through skin and other overlying tissues using animal specimens and living human subjects from depths of up to 4 mm. [11][12][13] Experiments looking at murine bone in vivo have been reported, [14] as have experimental refinements for the optics, the data analysis and the preparatory protocols. [15][16][17][18] These preparatory protocols include the application of glycerol as an optical clearing agent to reduce turbidity (i.e.…”

Developing fibre optic Raman probes for applications in clinical spectroscopy

“…39,96,98 In combination with this of course the volume of tissue sampled also increases and the depth resolution of the measurement decreases due to the diffuse scattering of light in tissues. Variants on the SORS design include inverse SORS, 27 where the illumination is delivered in a diffuse ring offset from a central collection area. Inverse SORS provides bulk sampling, and in spreading excitation photons over a larger sample area potential photodamage of the sample is reduced.…”

Recent advances in the development of Raman spectroscopy for deep non‐invasive medical diagnosis

“…However to accomplish this a very high laser illumination intensity was required, by about two to three orders of magnitude above the safe levels for illumination of skin. Instrumental complexity and cost were also prohibiting the wider use of this method in this area [50].…”

“…size and aspect ratio to particular dimensions of the analysed sample [49]. In a parallel pilot study, Matousek et al [50] demonstrated the basic feasibility of obtaining the Raman spectra of bones from humans in vivo. The measurements were performed under skin safe illumination conditions.…”