Optical detection of abnormally absorbing regions in tissue

Random walk theory is used to calculate a time-dependent contrast function to interpret data obtained from time-resolved transillumination detection of abnormally absorbing regions in tissue. The contrast function depends on the optical properties of the normal tissue as well as the absorptivity, size and location of the abnormal target. Results of the theory are applied to estimate the absorption coefficient of a cylinder target embedded in a tissue-like phantom. Extrapolation of the time-dependent contrast function to short times enables one to enhance the contrast and resolvability of the abnormal region.