Quantitative multilayered assessment of skin lightening by photoacoustic microscopy

Abstract

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.

Quantitative classification of melasma with photoacoustic microscopy: a pilot study

“…Each laser pulse generated an A-line signal in the imaging depth direction, and B-scan tomography image composed of continuous A-line signals was obtained by 2D transverse scanning. For the spatial resolution of the imaging system, our previous experiments showed that the PAM system has a lateral resolution of about 7 μm and an axial resolution of about 50 μm 28 , 33 …”

“…For the spatial resolution of the imaging system, our previous experiments showed that the PAM system has a lateral resolution of about 7 μm and an axial resolution of about 50 μm. 28,33 2.2 Data Processing and Statistical Analysis For 3D photoacoustic skin image reconstruction, each A-line signal is processed by median and filtering, then linearly projected to obtain a B-Scan image, and all B-Scan images are synthesized to display the 3D skin tissue structure. Normal 3D skin includes epidermis (stratum corneum and stratum basale), dermis, and subcutaneous tissue.…”

“…These skin layers are distributed at different depths and have different morphological structures, which can be distinguished by depth information. 28,32,40 In the quantitative melasma classification, to accurately distinguish the distribution characteristics of melanin and blood vessels in different skin layers, a skin tissue stratification algorithm based on MATLAB (R2019b, MathWorks) was programmed to accurately segment skin tissue at different depths. The specific implementation steps were as follows: first, a threshold value is set to reduce the influence of the background noise in the imaging system.…”

“…[12][13][14][15][16][17][18][19] In particular, photoacoustic microscopy (PAM) imaging modality enables label-free high-resolution quantitative imaging of the skin through high optical absorption in endogenous hemoglobin and melanin [20][21][22][23][24][25][26][27] and simultaneously reconstructs the three-dimensional (3D) morphological structure of melanin and blood vessels. [28][29][30] At present, PAM has been successfully applied in the clinical (preclinical) diagnosis of psoriasis, 31,32 port wine stain, 33,34 melanoma, 35,36 and other human skin diseases. [37][38][39] However, the imaging potential of PAM for melasma has not yet been demonstrated, especially in research on quantitative classification of lesion grading.…”

“…As a hybrid imaging technique, photoacoustic imaging (PAI) has shown great potential in clinical (preclinical) diagnosis 12 – 19 In particular, photoacoustic microscopy (PAM) imaging modality enables label-free high-resolution quantitative imaging of the skin through high optical absorption in endogenous hemoglobin and melanin 20 – 27 and simultaneously reconstructs the three-dimensional (3D) morphological structure of melanin and blood vessels 28 – 30 At present, PAM has been successfully applied in the clinical (preclinical) diagnosis of psoriasis, 31 , 32 port wine stain, 33 , 34 melanoma, 35 , 36 and other human skin diseases 37 …”