The use of Raman spectroscopy to identify and grade prostatic adenocarcinoma in vitro.

Raman spectroscopy is an optical technique that utilises molecular-specific, inelastic scattering of light photons to interrogate biological tissues (Mahadevan-Jansen et al, 1998). When tissue is illuminated with laser light, photons interact with intramolecular bonds present within the tissue. When occurs, the photon donates energy to or receives energy from the bond, producing a change in the bond's vibrational state. When it subsequently exits the tissue, the photon has an altered energy level and, therefore, has a different wavelength compared to the original laser light. This change in the photon's energy is known as the ‘Raman shift’ and is measured in wavenumbers. Photons interacting with different biochemical bonds within the tissue, undergo different Raman shifts, which taken together, form the ‘Raman spectrum’. The Raman spectrum is a plot of intensity against Raman shift, in wavenumbers. As the Raman Shift is inversely proportional to the change in the photons' wavelength, wavenumbers are expressed in units of cm−1. The Raman spectrum is a direct function of the molecular composition of the tissue and can therefore give a truly objective picture of the pathology. This is in contrast to Gleason grading, which is subjective and associated with considerable interobserver variation in reporting (Allsbrook et al, 2001a, 2001b). A previous study has confirmed that it is possible to record good-quality Raman spectra from prostatic tissue (Crow et al, 2002); this study evaluates the ability of Raman spectroscopy to differentiate between different prostatic pathologies in vitro.