Applicability of photoacoustic microscopy to quantitative photoaging evaluation

Skin aging caused by ultraviolet light exposure is one of the serious problems from the viewpoint of beauty and healthcare. This is because ultraviolet light can cause age spot, wrinkles, at the worst case, skin cancer and so on. To evaluate skin aging, various modalities are being used, such as histopathological diagnosis, optical imaging (e.g. optical coherence tomography (OCT), second harmonic tomography (SHG)) and ultrasound examination (B-mode imaging). However, they have disadvantages in terms of invasiveness, penetration depth and tissue specificity, respectively. To overcome these defects, photoacoustic imaging (PAI), a novel modality was used in this work. This modality can portray differences of tissue characteristics non-invasively. In this work, human skin tissues in various degrees of photoaging (8 subjects, 2 kind of site each) were measured by using acoustic resolution photoacoustic microscopy (AR-PAM) to verify the feasibility of quantitative skin aging evaluation with PA technique. The effects of photoaging progress on the signal intensity were investigated. The results demonstrated that the PA signal from the dermis increases as photoaging progresses. These analyses demonstrate the feasibility of quantitative skin aging evaluation with a PA imaging system.