Fluorometer for endoscopic diagnosis of tumors

A filter fluorometer suitable for endoscopic applications has been developed for detection and characterization of superficial tumors by the fluorescence of a previously injected, tumor-specific agent, hematoporphyrin derivative. Fluorescence is excited by violet light conducted through a fiberoptic lightguide in the endoscope, and the fluorescence emission together with reflected violet are collected by another fiberoptic lightguide. The red fluorescence and violet are separated by a dichroic mirror and filter and detected in photomultiplier tubes. The ratio of the fluorescence signal to the reflected violet signal is proportional to the ratio of the fluorescence yield to the violet reflectivity but is insensitive to variations in distance, angle, and violet power. The instrument may be useful for localizing small tumors, and for quantitative measurements of the amount of hematoporphyrin derivative in the tumor, a requirement for accurate dosimetry in photoradiation therapy.