MEASURING ABSORPTION-COEFFICIENTS IN SMALL VOLUMES OF HIGHLY SCATTERING MEDIA - SOURCE-DETECTOR SEPARATIONS FOR WHICH PATH LENGTHS DO NOT DEPEND ON SCATTERING PROPERTIES

The noninvasive measurement of variations in absorption that are due t o changes in concentrations of biochemically relevant compounds in tis sue is important in many clinical settings. One problem with such meas urements is that the path length traveled by the collected light throu gh the tissue depends on the scattering properties of the tissue. We d emonstrate, using both Monte Carlo simulations and experimental measur ements, that for an appropriate separation between light-delivery and light collection fibers the path length of the collected photons does not depend on scattering parameters for the range of parameters typica lly found in tissue. This is important for developing rapid, noninvasi ve, and inexpensive methods for measuring absorption changes in tissue . (C) 1997 Optical Society of America.