Fluorescence fiber optic probe with distance correction for endoscopic use

The introduction of fiber optics together with lasers has opened up many new areas of medicine, and in the case of the Fluorescent Fiber Optic Probe (hereafter Probe) make it possible to more selectively detect photosensitive drugs bound in tissue. In this case the fluorescent marker was formerly hematoporphyrin derivative (HpD), and has recently been inrnroved and replaced by dihemnatoporphyrin ether/ester (DHE) . ornmercially the drug is available under the trade name of Photofrin II Due to the small and flexible nature of the fibers themselves, fiber optics are an ideal tool to deliver and detect light through the biopsy channel of many commonly used endoscopes. In the case of the Probe a krypton laser operating in the violet region of the visible spectrum (406. 7 (36%) , 413 . 1(60%) , 415. 4 (4%)nm) is used as the exciting source to take advantage of the strong absorption peak of DHE around 410 nm. By monitoring the level of tissue autofluorescence (570 nm) and DHE fluorescence (690 nm) we are able to provide an output to indicate those areas where the fluorescent marker drug is localized while correcting for large variations in the fluorescence signal due to distance changes. Distance variations of the detecting fiber from the source are corrected for by ratioing the level of the two individual fluorescent signals received to provide a relatively linear fluorescent output reading with respect to individual channel readings and distance. The Probe is also designed to detect fluorescent drugs bound in tissue while working in the presence of the white light source used in endoscopy. The probe together with its own exciting light source (krypton laser) works as a stand alone device and does not require any modification or interlock with existing endoscopic equipment. Only the use of the biopsy channels of the endoscope are needed to insert the optical pick-up and delivery fibers.