Optical signatures of small, deeply embedded, tumor-like inclusions in tissue-like turbid media based on a random-walk theory of photon migration

Optical methods for detecting tumors in tissue are desirable in part because optical photons are non-ionizing. The highly scattering nature of tissue makes traditional, and even time-gated, optical imaging impractical for sites deeper than a few millimeters. Scattering in tissue causes dispersion in the path lengths of traversing photons which blurs images. With a theoretical description of path length dispersion, however, the perturbation caused by a localized anomaly may be identified from time-resolved intensity data. Random walk theory has been used to show a quantitative, closed-form relationship between the perturbation and the inclusion size and scattering properties relative to the background. Using Monte Carlo data, the authors show a method for analyzing the sensitivity of the relationship to signatures of small, deeply embedded, abnormally scattering inclusions.