Preliminary evaluation of two fluorescence imaging methods for the detection and the delineation of nasal cell carcinomas of the skin

Background and Objective: Fluorescence techniques can provide powerful noni nvasive means for medical diagnosis, based on the detection of either endog enous or exogenous fluorophores. The fluorescence of delta-aminolevulinic a cid (ALA)-induced protoporphyrin IX (PpIX) has already shown promise for th e diagnosis of tumors. The aim of the study was to investigate the localiza tion of skin tumors after the topical application of ALA, by detecting the PpIX fluorescence either in the spectral or in the time domain. Study Design/Materials and Methods: Two fluorescence imaging systems were u sed to identify basal cell carcinomas of the skin in humans, after topical application of 20% ALA ointment. Both systems rely on the comparison betwee n the exogenous and the endogenous fluorescence, performed either in the sp ectral domain or in the time domain. The first system works by using three images acquired through different spectral filters, whereas the second one measures the spatial map of the average fluorescence lifetime of the sample . Results: A clear demarcation of skin malignancies was successfully performe d in vivo noninvasively with both fluorescence imaging systems. Conclusion: The two complementary approaches considered in the present stud y show promise for skin tumor detection and delineation based on specific f luorescence features. (C) 2000 Wiley-Liss, Inc.