Abstract
BackgroundWe observed red autofluorescence emanating from bronchial cancer lesions using a sensitive color-fluorescence endoscopy system. We investigated to clarify the origin of the red autofluorescence.MethodsThe wavelengths of the red autofluorescence emanating from lesions were measured in eight patients using a spectrum analyzer and compared based on pathologic findings. Red autofluorescence at 617.3, 617.4, 619.0, and 617.1 nm was emitted by normal bronchus, inflamed tissue, tissue exhibiting mild dysplasia, and malignant lesions, respectively.Protoporphyrin, uroporphyrin, and coproporphyrin, the major porphyrin derivatives in human blood, were purchased to determine which porphyrin derivative is the source of red fluorescence when acquired de novo. We synthesized photoporphyrin, Zn-protoporphyrin and Zn-photoprotoporphyrin from protoporphyrin.ResultsCoproporphyrin and uroporphyrin emitted only weak fluorescence. Fluorescence was emitted by our synthesized Zn-photoprotoporphyrin at 625.5 nm and by photoprotoporphyrin at 664.0 nm.ConclusionsFrom these results, we conclude that Zn-photoprotoporphyrin was the source of the red autofluorescence observed in bronchial lesions. Zn-protoporphyrin is converted to Zn-photoprotoporphyrin by radiation with excitation light. Our results suggest that red autofluorescence emanating from Zn-photoprotoporphyrin in human tissues could interfere with photodynamic diagnosis using porphyrin derivatives such as Photofrin® and Lazerphyrin® with a sensitive endoscopy system, because color cameras cannot differentiate Zn-photoprotoporphyrin red fluorescence from that of other porphyrin derivatives.
Highlights
We observed red autofluorescence emanating from bronchial cancer lesions using a sensitive colorfluorescence endoscopy system
During the above clinical study, we detected red autofluorescence emanating from cancer lesions, contact bleeding sites, and blood vessels, and we reported that the red to green autofluorescence ratio (R/G ratio) was significantly higher in the cancer lesions [13]
Our results indicate that reduction in the intensity of 617.7-nm red autofluorescence emanating from the blood is necessary for reliable photodynamic diagnosis (PDD) using porphyrin derivatives and 5-aminolevulinic acid (5-ALA)
Summary
We observed red autofluorescence emanating from bronchial cancer lesions using a sensitive colorfluorescence endoscopy system. Components of the human body such as collagen, nicotinamide-adenine dinucleotide phosphate (NADP), and flavin-adenine dinucleotide (FAD), emit fluorescence when irradiated with light of an appropriate excitation wavelength [1, 2]. Cancerous lesions of the bronchus will be demonstrated by a reduction in the intensity of green autofluorescence when the lesions are observed using autofluorescence endoscopy. Several endoscopy systems have been developed for use in early detection of cancer lesions in the human bronchus. These systems include the LIFE lung [3, 4]
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