Optical spectroscopy mediated by fiberoptic probes can be used to perform minimally-invasive, real-time assessment of tissue pathology in-situ. Such techniques, sometimes called "optical biopsy," can serve as clinical diagnostic tools. A range of spectroscopies have been investigated for optical diagnosis, all of which have one basic principle in common: the specific optical spectrum of a tissue sample contains information about the biochemical composition and/or the structure of the tissue. This basic approach is useful not only for the detection of cancer, but may also be used for other diagnostic applications such as blood oxygen saturation and intra-luminal detection of atherosclerosis. Special interest, however, has been given to the detection of early carcinoma and premalignant conditions. Spectroscopies based on fluorescence (both autofluorescence and exogenous-agent fluorescence), Raman scattering, and elastic light scattering have been investigated clinically. The most common approaches have been based on UV-induced fluorescence spectroscopy and Raman spectroscopy, which are assumed to be responsive to biochemical changes in cells. On the other hand, the method of elastic-scattering spectroscopy (ESS) is sensitive to the sub-cellular architectural changes, such as nuclear grade and nuclear to cytoplasm ratio, mitochondrial size and density, etc., which correlate with features used by pathologists when performing histological assessment. The ESS method senses those morphology changes in a semi-quantitative manner, without actually imaging the microscopic structure. The fiber probe geometry is illustrated in Figure 1.
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