Tissue diagnostics using laser-induced fluorescence

We have performed extensive investigations of laser-induced fluorescence in animal and human tissue aimed at instant tissue characterization. Autofluorescence, as well as specific fluorescence from HPD/DHE and other photosensitizers, has been utilized. The studies have been focused on the demarcation of malignant tumours and atheroscleortic plaques. A nitrogen laser or an excimer-pumped dye laser was used to induce fluorescence, which was analysed with an intensified optical multichannel system. A fibre-optic sensor system was developed for the clinical work. Multi-colour fluorescence imaging has also been demonstrated along a line and equipment for two-dimensional imaging is being constructed. Dimensionless spectroscopic functions, which are not affected by factors that are clinically uncontrollable have been employed for optimum tissue discrimination. The investigations have so far been performed in a time-integrated mode, but time-resolved studies are now being initiated to fully exploit the diagnostic power of tissue laser-induced fluorescence. In addition to a presentation of our own work a brief review of tissue fluorescence studies performed by other groups is also given.