Nonlinear Microscopy in Clinical Dermatology

Nonlinear optical microscopy has the potential of being used in vivo as a noninvasive high-resolution imaging modality for skin examination at both epidermal and dermal levels. In particular, two-photon fluorescence microscopy can be used to detect morphological and functional changes in the epidermis via the high signal generated by the reduced form of mitochondrial nicotinamide adenine dinucleotide (NADH) [49]. This microscopic modality allows differentiation of epidermal layers with different structural and cytological features. Further, the combination of two-photon fluorescence with second harmonic generation microscopy can be successfully employed for dermal imaging. In particular, the two mentioned imaging techniques are able to selectively image elastic fibers and collagen, hence providing an exhaustive characterization of the skin dermis. In conclusion, nonlinear imaging techniques, especially if used with a multimodal approach, could find a stable place in a clinical dermatological setting for both diagnosis and follow-up purposes.