Quantitative multilayered assessment of skin lightening by photoacoustic microscopy.

BACKGROUND: With the emergence of various new skin-lightening products, there is an urgent need to scientifically evaluate the efficacy and toxicology of these products, and provide scientific guidance for their use based on physiological differences between individuals. Visualized imaging methods and quantitative evaluation criteria play key roles in evaluating the efficacy of skin-lightening products. In order to quantify the changes in the multilayered morphology and endogenous components of human skin before and after the use of lightening products, high-resolution three-dimensional (3D) imaging of human skin is required. METHODS: In this study, photoacoustic microscopy (PAM; SSPM-532, Guangdong Photoacoustic Medical Technology Co., Ltd.) was used to capture the morphological structures of human skin and reveal skin components quantitatively. The efficacy and safety of skin-lightening products were evaluated by measuring skin melanin concentration and observing skin morphology. The melanin concentration in the epidermis was obtained by examining the linear relationship between photoacoustic (PA) signals. Further, the epidermal thickness and the melanin distribution were obtained in the cross-sectional (x-z) and lateral (x-y) images. Finally, the efficacy of skin-lightening products was evaluated according to the concentration and distribution of melanin in the epidermis, and the safety of cosmetics was assessed by observing the vascular morphology in the dermis. RESULTS: PAM noninvasively could assess the multilayered morphological structures of human skin, which allowed for quantification of epidermal thickness and melanin concentration of different skin sites. Based on this, the efficacy and safety of skin-lightening products in multilayer structures were quantitatively evaluated. CONCLUSIONS: As a quantitative imaging method, PAM, has the potential to accurately evaluate the use of skin-lightening products. The method can also be extended to assessments within the larger field of aesthetic medicine.

Reliability assessment on intravascular photoacoustic imaging of lipid: ex vivo animal and human sample validation.

Although the lipid-detecting IVPA imaging system has been developed in resolution, speed, and catheter size, there is no parameterization study of the reliability on the IVPA imaging for lipid diagnosis. Here, the sensitivity, specificity, and accuracy were calculated to assess the reliability of the IVPA imaging of lipid. Abdominal aortas from six rabbits with atherosclerosis, were subjected to the IVPA imaging and Oil Red O staining, and 75 groups of IVPA as well as corresponding histological images were obtained. Similarly, 125 groups of IVPA and histological results were obtained from five human carotid plaque samples. The sensitivity, specificity, and accuracy, calculated from the statistical data, were 96.8%, 83.3%, 94.6% and 97.3%, 72.7%, 95.2%, respectively. The numerical values of sensitivity, specificity, and accuracy demonstrated the reliability of IVPA imaging on distinguishing the lesions vessel with lipid-rich plaque, which provided the foundation for IVPA translation to clinical application.