Analytical solutions for time-resolved fluorescence lifetime imaging in a turbid medium such as tissue.

An analytical solution is developed to quantify a site-specific fluorophore lifetime perturbation that occurs, for example, when the local metabolic status is different from that of surrounding tissue. This solution may be used when fluorophores are distributed throughout a highly turbid media and the site of interest is embedded many mean scattering distances from the source and the detector. The perturbation in lifetime is differentiated from photon transit delays by random walk theory. This analytical solution requires a priori knowledge of the tissue-scattering and absorption properties at the excitation and emission wavelengths that may be obtained from concurrent time-resolved reflection measurements. Additionally, the solution has been compared with the exact, numerically solved solution. Thus the presented solution forms the basis for practical lifetime imaging in turbid media such as tissue.

Quantification by random walk of the optical parameters of nonlocalized abnormalities embedded within tissuelike phantoms.

We have extended a random-walk theory that uses time-dependent contrast functions to quantify the cross section and the corrected scattering and absorption coefficients of abnormal nonlocalized targets from time-of-flight (TOF) data obtained in time-resolved transillumination experiments. Experimental TOF's are used to show that this newly developed random-walk method is able to quantify the size and the optical properties of embedded nonlocalized targets in with an error rate of