Time-resolved reflectance measures the escape of photons that have been injected into a scattering medium by a very short laser pulse. In this paper, such measurements are discussed in terms of the basic equations governing the escape of photons from turbid tissue, and an experimental example of a prototype endoscopic device is given.
S. L. Jacques, S. T. Flock, "Time-resolved reflectance spectroscopy," SPIE Proceedings of Future Trends in Biomedical Applications of Lasers, edited by L. O. Svaasand, 1525, 35-40 (1991).