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Methods for the endoscopic photographic and visual detection of helium cadmium laser‐Induced fluorescence of photofrin II

Endoscopic detection of small tumors is key to the early diagnosis and treatment of malignancy. This paper describes a simple, endoscopic detection system which enables tumor localization and a permanent record based on the laser–induced fluorescence of dihematoporphyrin ether (LIFD). Spectral analysis of dihe‐matoporphyrin ether (DHE, Photofrin II) was performed with a Perkin Elmer LS‐5 scanning fluorimeter. DHE at concentrations of 50 μg/ml and 5 μg/ml in 95% ethanol were tested, demonstrating fluorescence quenching at 50 μg/ml DHE at 406 nm excitation. This phenomenon was not observed at 442 nm excitation. Based on this data and the availability of the helium cadmium laser, a series of endoscopic detection systems was developed and tested utilizing a LiConix 4240NB helium cadmium laser (TEMoo, 442 nm, 40 mW). A fiber with a microdiverging (MDL) lens was used. Irradiance achieved at the tip of the fiber was 31.58 mW/cm2 for MDL. A Corning 34832 (550 nm) sharp cutoff barrier filter was coupled to an Olympus OES BF2T10 bronchoscope. Successful detection of LIFD was obtained.