Deep Raman

One of the main problems with the use of Raman spectroscopy for in vivo measurements of biological tissue is that the collected Raman signal decreases when probing at greater tissue depth, causing the surface Raman signal and fluorescence to be significantly stronger than the sub-surface Raman signal. It is possible to obtain biochemical information from beneath the tissue surface by using a number of novel techniques. Previous work by ourselves (in collaboration with Pavel Matousek at the Rutherford Appleton Laboraory) and others has demonstrated the potential for depth probing in biological tissues, by effectively suppressing the relative signal level from the surface and thus enhancing the relative signal level from the depth of interest. A number of approaches have been used, ranging from time gating of the collected signal (Kerr-gating) following a picosecond laser pulse; to spatially offsetting the point of collection from the point of illumination (SORS); to transmission Raman spectroscopy, which has so far achieved the deepest penetration depth (~3cm) into biological tissue.

2005 Hart Prieto, et al, (Kerr-gate) JBO, 10, 4.
2007 Baker, R, et al, (Kerr-gate), Analyst, 132, 48 - 53.
2007 Stone, N, et al, (SORS), Analyst, 132, 899 - 905.
2007 Matousek, P, et al (Transmission Raman), Journal of Biomedical Optics.
2008 Stone, N, et al (Advanced TransRam), Cancer Research.