Multiscale confocal photoacoustic dermoscopy to evaluate skin health.

Background: Photoacoustic dermoscopy (PAD) is a promising branch of photoacoustic microscopy (PAM) that can provide a range of functional and morphologic information for clinical assessment and diagnosis of dermatological conditions. However, most PAM setups are unsuitable for clinical dermatology because their single-scale mode and narrow frequency band result in insufficient imaging depth or poor spatiotemporal resolution when visualizing the internal texture of the skin. Methods: We developed a multiscale confocal photoacoustic dermoscopy (MC-PAD) with a multifunction opto-sono objective that could achieve high quality dermatological imaging. Using the objective to coordinate the spatial resolution and penetration depth, the MC-PAD was used to visualize pathophysiological biomarkers and vascular morphology from the epidermis (EP) to the dermis, which enabled us to quantify skin abnormalities without using exogenous contrast agents for human skin. Results: The MC-PAD was shown to have the ability to differentiate between different types of cells (such as red blood cells and melanoma cells), image and quantify pigment of the skin, and visualize skin morphology and blood capillary landmarks. The MC-PAD detected a significant difference in the structures of some pigmented and vascular lesions of skin diseases compared with that of healthy skin (P<0.01). The café au lait macule (CALM) skin type was found to have a relatively higher melanin concentration and thicker stratum basale (SB) in the EP than healthy skin. The dermal vascular network of skin that had a port wine stain (PWS) had greater diameters and a denser distribution than healthy skin, as reported in clinical trials. Conclusions: The MC-PAD has a broad range of applications for the diagnosis of human skin diseases and evaluation of the curative effect of treatments, and it can offer new perspectives in biomedical sciences.