Laser-induced fluorescence studies of normal and malignant tumour tissue of rat following intravenous injection of delta-amino levulinic acid

Background and Objective: Laser-induced fluorescence was studied in normal and tumour tissue of rat after intravenous injection of delta-amino levulinic acid (ALA). The aim of the study was to investigate the protoporphyrin IX accumulation in different tissue types in rat after systemically administered ALA. Study Design/Material and Methods: A malignant rat tumour and normal tissue from 13 different organs were investigated in eight rats. The rats were injected with two different ALA doses, 30 and 90 mg/kg b.w., and the investigations were performed at 10, 30, and 240 min after the injection. The fluorescence was recorded utilising an optical fibre based fluorosensor at 405 nm excitation. Results: Fluorescence spectra were recorded in the 400-750 nm wavelength region including the dual-peaked PpIX fluorescence at about 635 and 705 nm, and the tissue autofluorescence peaking at about 500 nm, The maximum tumour build-up of PpIX was achieved already in less than 1 hr after ALA injection. The fluorescence demarcation between tumour and surrounding tissue was a factor of 7-8:1 after 30 min and decreased for longer retention times. The accumulation in 13 different organs was investigated and a particularly high PpIX build-up was found in stomach and intestine. Conclusions: Fluorescence detection following i.v. injection of ALA provides attractive diagnostics for the experimental tumour used, indicating clinical usefulness. (C) 1997 Wiley-Liss, Inc.