Abstract

Fluorescence imaging can be applied to localize a specific endogenous or exogenous fluorophore in organic tissues. This technique is specially promising for tumor detection since some compounds localize in malignant tissues in a higher concentration than in surrounding healthy ones.^1,2 Continuous wavelength fluorescence imaging suffers from drawbacks that hamper its application; for example, sharp cut-off filters must be used to suppress the excitation light and narrowband filters are often, required to separate the fluorescence of interest from background fluorescence and stray light. Further, the measurements must be done in absolute darkness. To overcome these limitations, we propose an acquisition technique that operates in the time domain.^3,4 An intensified video-camera acquires only the fluorescence light that falls within a shorttime window, suitably delayed with respect to the pulsed laser excitation. The width of the acquisition window can be set down to 5 ns. The experimental set-up includes a nitrogen-pumped dye laser that generates subnanosecond pulses at a tunable wavelength, a precision pulse/delay generator to set the required synchronization, and an image processing system placed in a computer. Real time image enhancement is available through a dedicated software.

© 1993 Optical Society of America