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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.
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