In vivo detection of basal cell carcinoma using imaging spectroscopy.

Photodynamic therapy has become an interesting alternative to conventional therapy for basal cell carcinomas. Delta-aminolevulinic acid is a precursor in the biosynthesis of protoporphyrin IX that accumulates to a large extent in tumour tissue. We have compared in vivo protoporphyrin IX fluorescence with the extent of basal cell carcinomas on the face, trunk and thigh determined by histological mapping in 30 lesions in 22 patients. A new non-laser based set-up was used to record the fluorescence images. Delta-aminolevulinic acid was applied for 4 h inducing high concentrations of protoporphyrin IX. Routine vertical histological sections and Mohs micrographic surgery were used to map the extent of the tumours. In 50% of lesions we found a good correlation between the fluorescence imaging and histological mapping. In 23% the correlation was partial. In the other lesions we found no correlation at all. This method may be used to delineate basal cell carcinomas more accurately than current methods.