Optical Spectroscopy for In Vivo Estimation of Hemodynamics and Structural Properties of the Brain

A non-contact optical spectroscopy system was developed, using a wide-field illumination, to study the human brain in vivo. The optical signal recorded from a point on the exposed brain surface using this new system was a fraction of the total reflectance RTm(?). The system was designed to be used in conjunction with a reflectance standard with known optical properties in order to convert RTm(?) to the absolute total reflectance RTA(?). Furthermore, a new Monte-Carlo -based spectral interpretation algorithm was developed to retrieve hemodynamic and structural properties from RTA(?). Specifically, the algorithm was able to produce the ratio of the absorption and reduced scattering spectra (i.e., ?a(?)/?s´(?)), the level of hemoglobin oxygenation, and the scattering power. . A reflectance standard that can be used in conjunction with the non-contact spectroscopy system for in vivo measurements of RTA(?) was also developed. The system is currently used in the in vivo studies of pediatric brain tumors and epileptic lesions.