Kinetic fluorescence studies of 5-aminolaevulinic acid-induced protoporphyrin IX accumulation in basal cell carcinomas

Laser-induced fluorescence (LIF) investigations have been performed in conn ection with photodynamic therapy (PDT) of basal cell carcinomas and adjacen t normal skin following topical application of 5-aminolaevulinic acid (ALA) in order to study the kinetics of the protoporphyrin TX (PpIX) build-up. F ive superficial and 10 nodular lesions in 15 patients are included in the s tudy. Fluorescence measurements are performed prior to the application of A LA, 2, 4 and 6 h port ALA application, immediately post PDT (60 J cm(-2) at 635 nm), and 2 h after the treatment. Hence, the build-up, photobleaching and re-accumulation of PpIX can be followed. Superficial lesions show a max imum PpIX fluorescence 6 h post ALA application, whereas the intensity is a lready the highest 2-4 h after the application in nodular lesions. Immediat ely post PDT, the fluorescence contribution at 670 Mm from the photoproduct s is about 2% of the pre-PDT PpIX fluorescence at 635 nm. Two hours after t he treatment, a uniform distribution of PpIX is found in the lesion and sur rounding normal tissue. During the whole procedure, the autofluorescence of the lesions and the normal skin does not vary significantly from the value s recorded before the application of ALA. (C) 1999 Elsevier Science S.A. Al l rights reserved.