Fluorescence lifetime imaging distinguishes basal cell carcinoma from surrounding uninvolved skin

Background  Fluorescence lifetime imaging (FLIM) is a novel imaging technique that generates image contrast between different states of tissue due to differences in fluorescence decay rates.
Objectives  To establish whether FLIM of skin autofluorescence can provide useful contrast between basal cell carcinomas (BCCs) and surrounding uninvolved skin.
Methods  Unstained excision biopsies of 25 BCCs were imaged en face with FLIM following excitation of autofluorescence with a 355 nm pulsed ultraviolet laser.
Results  Using FLIM we were able to distinguish areas of BCC from surrounding skin in an ex vivo study. Significant reductions in mean fluorescence lifetimes between areas of BCC and areas of surrounding uninvolved skin were demonstrated ( P  <   0·0001). These differences were apparent irrespective of the decay model used to calculate the fluorescence lifetimes (single vs. stretched exponential) or the long-pass filter through which the emitted autofluorescence was collected (375 vs. 455 nm). Conversely, there was no significant difference between the BCC and uninvolved areas of each sample when mean autofluorescence intensities were examined. Moreover, wide-field false-colour images of fluorescence lifetimes clearly discriminated areas of BCC from the surrounding uninvolved skin.
Conclusions  We therefore believe that FLIM has a potential future clinical role in imaging BCCs for rapid and noninvasive tumour delineation and as an aid to determine adequate excision margins with best preservation of normal tissue.