Raman Spectroscopy in Medicine

One can observe recently a remarkable increase in the application of Raman spectroscopy to the field of medicine. The reason is that Raman, like IR spectroscopy, is a vibrational spectroscopic technique capable of providing details on the chemical composition, molecular structure, and corresponding molecular interactions in cells and tissues. As diseases progressed, clearly identifiable changes in the molecular composition of affected tissues changes are reflected (or becomes “visible”) in Raman spectra. In a case then the spectral changes are inherent (specific) for a particular disease state, they can, in principle, be used as phenotypic markers or signs of the disease. Many studies in the literature have illustrated that differences can be observed between ex vivo Raman spectra of healthy and diseased tissues. The majority of these studies are only exploratory in nature. Nevertheless, the clear message is that clinical diagnostic tools can be successfully developed from the Raman spectroscopic fingerprints of tissues. Raman spectroscopy has recently been applied ex vivo and in vivo to address various biomedical issues such as the early detection of cancers, monitoring of the effect of various agents on the skin, determination of atherosclerotic plaque composition, and rapid identification of pathogenic microorganisms. Nowadays Raman spectroscopy becomes a potentially important clinical tool for real-time diagnosis of disease and in situ evaluation of living tissue. The purpose of this chapter is to review the biological and physical basis of Raman spectroscopy of tissue, to assess the current status of the field, and to explore future directions. The principles of Raman spectroscopy and the information it provides on molecular level are briefly explained. The authors try to present an overview of the evolution of Raman spectroscopic techniques in biology and medicine, from early investigations using visible laser excitation to present-day technology based on near-infrared laser excitation and charge-coupled device array detection. State-of-the-art Raman spectrometer systems both for research laboratory and for clinical settings are described. Modern methods of multifunctional spectral analysis for extracting diagnostic, chemical, and morphological information are reviewed. Several in-depth applications are presented to illustrate the methods of collecting, processing, and analyzing data. Various clinical applications of Raman spectroscopy, as well as some directions for future are discussed.