Multiphoton Laser Microscopy and Fluorescence Lifetime Imaging for the Assessment of the Skin

Abstract

Multiphoton laser microscopy or tomography associated to fluorescence lifetime imaging (MPT/FLIM) is an emerging noninvasive imaging method enabling an in vivo ‘optical biopsy’. Thanks to its spatial resolution similar to that of histopathology at high power magnification (<1 μm lateral, <2 μm) and to the possible use of colour coding of the fluorescence decay time, this technique enables the morphology of the tissue to be immediately recognizable. MPT/FLIM is particularly suited to study the ageing process of the dermis, enabling an in vivo distinction between collagen fibres and the elastotic material in the extracellular matrix of the dermis. It also holds great promise for increasing diagnostic accuracy of skin tumours. Thanks to the recognition of morphologic parameters and the study of fluorescence lifetime modifications in cancer cells, basal cell carcinoma (BCC) cells can be distinguished from normal keratinocytes, enabling both a diagnosis of BCC and the identification of tumour margins. Melanin-containing cells can be identified based on the short fluorescence lifetime decay characteristics of melanin. This contributes to the recognition of melanocytes in healthy skin and benign and malignant melanocytic lesions.