Neuro-oncological applications of optical spectroscopy

Advances in optics and molecular imaging have occurred rapidly in the past decade. One technique poised to take advantage of these developments is optical spectroscopy (OS). All optical spectroscopic techniques have in common tissue interrogation with light sources ranging from the ultraviolet (UV) to the infrared (IR) ranges of the spectrum, and collection of information on light reflected (reflectance spectroscopy) or light interactions with tissue and emergence at different wavelengths (fluorescence and Raman spectroscopy). OS can provide information regarding intrinsic tissue optical properties such as tissue structure, nuclear density, and the presence or absence of endogenous or exogenous fluorophores. Among other applications, this information has been used to distinguish tumor from normal brain tissues, to detect tumor margins in intrinsic, infiltrating gliomas, to identify radiation damage to tissues, and to assess tissue viability and predict the onset of apoptosis in vitro and in vivo. Potential applications of OS include detection of specific central nervous system (CNS) structures, such as brain nuclei, identification of cell types by the presence of specific neurotransmitters, and the detection of optically labeled cells or drugs during therapeutic interventions. All have potential utility in neuro-oncology, have been investigated in our laboratories, and will be the subject of this review.