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study of 5-aminolevulinic acid induced flourescence in the canine oral cavity
Study of five aminolevulinic acid induced flourescence in the canine oral cavity
xii, 121 leaves : illustrations ; 28 cm.
There has been an increasing interest in the use of fluorescence spectroscopy to detect premalignant and malignant changes in various type of tissues. Photodynamic therapy is rapidly becoming an accepted therapeutic modality for certain types of tumors. Thus there is a need for a safe photosensitizer that could enhance the spectroscopic contrast between normal and neoplastic tissue, while allowing for selective photosensitization and treatment of pre-malignant and malignant lesions in the oral cavity. In the first experiment, the pharmacokinetics of 5aminolevulinic acid (ALA) induced protoporphyrin IX (PPIX) in the biosynthetic pathway, were investigated. Dogs were randomly administered five doses of ALA: 5, 25, 50, 75, and 100 mg/kg. A "washout 'period of I week between administration of each dose was allowed to ensure against PPIX build-up. The fluorescence (636 nm) from the oral cavity was detected with a fiber optic probe coupled to an optical multichannel analyzer, at 3 sites: buccal mucosa, gums and the tongue, and also from a remote site, the skin. Results showed that different tissues have different pharrnacokinetic response, the tongue and the gums showed the highest peak fluorescence followed by the buccal mucosa and the skin. The second experiment provided preliminary information regarding the toxicity of the ALA doses. Serum hepatic enzymes were evaluated ten days after administration of dose. The study suggests that ALA appears to be safe in dogs at doses of 25-100 mg/kg. Future studies on the potential ALA-induced hepatotoxicity may be required in dogs, prior to the use of higher doses. In the final experiment, the use of ALA-induced fluorescence ratio to differentiate between normal, and gingivitis-affected gingiva, is investigated. Five dogs with varying degrees of gingivitis were administered 25 mg/kg of ALA intravenously. Autofluorescence and ALAinduced fluorescence from 3 sites: normal gingiva, pigmented gingiva, and gingivitis, were recorded. Four dogs showed higher and earlier ALA-induced fluorescence from the gingivitis site as compared to the unpigmented gingiva. Fluorescence from the pigmented gingiva was found to be the lowest. ALA-induced fluorescence has potential to serve as a diagnostic tool in the detection of oral cancer.
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Includes bibliographical references: pages 98-107.