Abstract

The medical community has a strong interest in developing new, more sophisticated techniques for smart, non-invasive methods of detecting disease. This article describes a potentially new medical tool called optical biopsy. Over the past ten years, researchers at the City College of New York (CCNY) have been developing spectroscopic techniques for an optical biopsy approach to evaluate, diagnosis and characterize tissue.^1,2 Optical biopsy techniques do not require the removal of tissue from the body. They are based on the analysis of a biomedical sample through its characteristic optical properties as shown in Fig. 1. By illuminating a tissue sample and analyzing the “colors” of the light which the sample emits or scatters in response to this optical excitation, one is are able to determine the state of the tissue - normal, benign, precancerous or cancerous. Fluorescence^1-7 and Raman^8-11 processes are potential optical biopsy methods. In fluorescence spectroscopy, one measures the allowed electronic transitions, while Raman spectroscopy is sensitive to the vibrational transitions from various groups of molecules. When a photon is absorbed in tissue, the excited molecule can return to the ground state by radiation Fig. 2 schematically shows the transitions for absorption, fluorescence, Raman and phosphorescence. The spectrum of the light emitted gives information about the presence of different molecules or structural changes that occur in the tissue and hence, the state of the tissue. The change in state from normal to cancerous alters tissue structure and composition and thus alters the spectrum of emitted and scattered light.

© 1996 Optical Society of America