Mapping the fluorescence yield on turbid media

In this letter, we introduce a combined polarization and fluorescence imagi ng technique for the measurement of fluorescence yield on the surface of tu rbid media. We use the cross-polarization method to reject the specular ref lection and enhance the diffusive backscattering from the turbid media. It has been found that the ratio image of fluorescence versus cross-polarized reflection is not sensitive to the geometry of fluorescence excitation and illumination, and provides a map of fluorescence yield on the surface of im aged subject. The technique reported in this letter may potentially solve t he problem for imaging of early cancers which usually start from the superf icial layer of tissue and have the fluorescence yield lower than surroundin g normal tissue. (C) 2000 American Institute of Physics. [S0003-6951(00)008 08-1].