Localization of luminescent inhomogeneities in turbid media with spatially resolved measurements of cw diffuse luminescence emittance

We present a steady-state method for localizing a source of luminescence (i.e., fluorescence or phosphorescence) buried in a semi-infinite turbid medium with unknown optical properties. A diffusion theory expression describing the emittance of an isotropic point source is fit to spatially resolved surface measurements of the diffuse emittance from the luminescent source. The technique reports the location of the center of a 6.0-mm-diameter, fluorophore-containing spherical bulb embedded in a liquid phantom with an accuracy of 1.0 mm or better for source depths as great as 40.0 mm. Monte Carlo data are analyzed to investigate the range and the possible sources of error in the reconstructed source depth.