Multiphoton microscopy: a new paradigm in dermatological imaging.

In recent years, the non-linear optical imaging technique of multiphoton microscopy has gained significant popularity in biomedical imaging. Since optical imaging can provide detailed morphological information of biological structures, multiphoton microscopy holds great promise as a potential clinical diagnostic tool of dermatological conditions. In this review, we will begin by discussing the basic principles of multiphoton microscopy, including the process of fluorescence and second harmonic generation. In addition, we will present the dermatological applications of multiphoton imaging, including the diagnosis of basal cell carcinoma and the evaluation of skin photoaging. We also describe applications of this technique to transcutaneous drug delivery, melanoma imaging, skin diseases associated with extracellular matrix alterations and cutaneous microvascular observation. Finally, we will discuss the additional issues that need to be resolved before multiphoton imaging can become a major diagnostic tool in clinical dermatology.