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Combined time- and depth-resolved autofluorescence spectroscopy for tissue diagnosis

A fluorescence spectroscopy system combining depth- and time-resolved measurements is developed to investigate the layered fluorescence temporal characteristics of epithelial tissue. It is found that esophageal tissue structure can be resolved well by means of the autofluorescence time-resolved decay process with 375-, 405- and 435- nm excitation. The decay of the autofluorescence signals can be accurately fitted with a dual-exponential function consisting of a short lifetime (0.4 ~ 0.6 ns) and a long lifetime (3 ~ 4 ns) components. The short lifetime component dominates the decay of normal epithelial fluorescence while the decay of the signals from keratinized epithelium and stroma are mainly determined by the long lifetime component. The ratio of the amplitudes of two components provides the information of fine structure of epithelial tissue. This study demonstrates that the combined depth- and time-resolved measurements can potentially provide accurate information for the diagnosis of tissue pathology.