Autofluorescence endoscope systems demonstrate high sensitivity for the detection of cancerous or precancerous lesions. These areas are indicated by a reduction in the level of tissue autofluorescence. Visual detection of such regions is straightforward but often results in false positive readings since there are benign conditions which can cause the same effect. A method which results in a high number of false positive readings is described as one with low specificity. To improve the specificity of autofluorescence endoscopy additional information beyond a visual assessment of the reduction in fluorescence intensity can be taken. Spectral information, resulting from the dispersion or filtering of the intrinsic fluorescence and/or white light reflected from the tissue has been shown to be effective at diagnosing cancerous tissue. Similarly, information available from measurements of light scattering in the tissue can be used to classify tissue types and measure the concentration of important tissue components such as hemoglobin. This information has been correlated to the presence or absence of cancerous lesions. In the past such information has been available from fiberoptic spectroscopic probes passed through the biopsy channel of an endoscope and brought into direct contact with the tissue under video observation. This program will develop a non-contact spectroscopic probe that will be fixed in position at the distal tip of an autofluorescence endoscope. There are numerous advantages for a non-contact spectroscopic probe used in conjunction with the autofluorescence endoscope. If the probe is built into the endoscope it is always available. If the probe does not contact the tissue it cannot cause a false reading by damaging the tissue surface and raising a layer of blood (which readily absorbs fluorescence). Tissue scattering is more easily measured with non-contact probes because this scattering is sensitive to local pressure. Handling of a non-contact probe is easier because the area being examined spectroscopically can be indicated visually on the endoscope imaging display and positioned by adjusting the direction of the distal tip. The design of this probe allows it to be used in existing endoscopes by fitting it into a standard biopsy channel. The optical components required to be within the endoscope itself are small and passive so that, in the future, it may be built into new endoscope designs. These probes will improve the specificity of autofluorescence detection of cancers and precancers which will reduce the number of unnecessary biopsies. This, in turn, will reduce the risk to patients, reduce the time required for autofluorescence procedures and reduce clinical costs as well.
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