Line-field confocal optical coherence tomography coupled with artificial intelligence algorithms to identify quantitative biomarkers of facial skin ageing.

Quantitative biomarkers of facial skin ageing were studied from one hundred healthy Caucasian female volunteers, aged 20-70 years, using in vivo 3D Line-field Confocal Optical Coherence Tomography (LC-OCT) imaging coupled with Artificial Intelligence (AI)-based quantification algorithms. Layer metrics, i.e. stratum corneum thickness (SC), viable epidermal thickness and Dermal-Epidermal Junction (DEJ) undulation, as well as cellular metrics were measured for the temple, cheekbone and mandible. For all three investigated facial areas, minimal age-related variations were observed in the thickness of the SC and viable epidermis layers. A flatter and more homogeneous epidermis (decrease in the standard deviation of the number of layers means), a less dense cellular network with fewer cells per layer (decrease in cell surface density), and larger and more heterogeneous nuclei within each layer (increase in nuclei volume and their standard deviation) were found with significant variations with age. The higher atypia scores further reflected the heterogeneity of nuclei throughout the viable epidermis. The 3D visualisation of fine structures in the skin at the micrometric resolution and the 1200 µm × 500 µm field of view achieved with LC-OCT imaging enabled to compute relevant quantitative biomarkers for a better understanding of skin biology and the ageing process in vivo.

Why women use makeup: implication of psychological traits in makeup functions.

Makeup acts and stimulates three of our senses: touch (which encompasses all sensations from the body surface), smell (fragrance), and sight (the process of becoming and looking beautiful). The positive stimulation of these senses by makeup can induce sensory as well as psychological pleasure. In order to understand the relationship of women to their makeup, we interviewed different groups of women on their quality of life and makeup habits. Then, through four standard well-validated psychometric self-questionnaires, we examined the possible relation between the need to make up oneself and specific psychological features. Our first results clearly showed that makeup could support two opposite "up" functions, i.e., "camouflage" vs "seduction." Concerning their psychological profiles, results showed that women of the functional class "camouflage" are more anxious, defensive, and emotionally unstable compared to those of the functional class "seduction," who appear to be more sociable, assertive, and extroverted. Further analyses revealed a division of the two classes into subclasses of volunteers with opposed personality and psychological profiles. This new classification allowed us to define more precisely the relations existing within the subjective experience of women during the makeup process. In conclusion, our study revealed that beyond the simple application of colorful products on the face, makeup has two major functional implications depending on specific psychological profiles of women.

Quantitative assessment of properties of make-up products by video imaging: application to lipsticks.

BACKGROUND/AIMS: The different properties and visual effects of lipstick have been studied by image analysis directly on volunteers. METHODS: After controlling the volunteer's position mechanically using an ophthalmic table and visually using an acquirement mask, which is an indicator of luminance and guide marks, we carried out video colour images of the make-up area. From these images, we quantified the colour, gloss, covering power, long-lasting effect and streakiness, using computer science programs. RESULTS/CONCLUSION: Quantitative colorimetric assessment requires the transformation of the RGB components obtained by a video colour camera into CIELAB colorimetric space. The expression of each coordinate of the L*a*b* space according to R,G,B was carried out by a statistical method of polynomial approximations. A study, using 24 colour images extracted from a Pantone(R) palette, showed a very good correlation with a Minolta Colorimeter(R) CR 300. The colour assessment on volunteers required a segmentation method by maximizing the entropy. The aim was to separate the colour information sent back by the skin to the make-up area. It was very useful to precisely delimit the contour between the skin and the product in the case of almost identical colours and to evaluate the streakiness. From this colour segmentation, an algorithm was studied to search for the shades most represented in the overall colour of the make-up area. The capacity to replicate what the consumer perceives of the make-up product, to carry out studies without having any contact with the skin surface, and the constant improvement of software and video acquirement systems all make video imaging a very useful tool in the quantitative assessment of the properties and visual effects of a make-up product.

Characterization and quantification of the skin radiance through new digital image analysis.

BACKGROUND/AIMS: The individual perception of the radiance is difficult to define and quantify because it often includes physiological and psychological attributes. Although if they are differences in the perception of the skin radiance, dermatologists and experts in cosmetology consider that the complexion must reflect the general health of an individual. The aim of this work was to determine existing conditions of skin radiance via digital image analysis, consumer's perception and experts' evaluation, and propose a mathematical model to quantify the global radiance phenomenon. METHODS: A round table meeting was organized in order to have free discussions about skin radiance. The qualitative assessment of skin radiance was carried out using a self-assessment questionnaire constructed according to the information obtained from the round table meeting. A simplified version of this questionnaire was proposed to experts. One hundred female subjects belonging to three different age groups (20-30, 30-40, 40-50 and >50 years old) participated in the study. Facial images were taken using a video imaging with visual control system to ensure consistency of images among volunteers. From these images, algorithms based on the principle of polynomial approximation, segmentation by maximalization of the entropy and the Logarithmic Image Processing model were required to extract skin radiance parameters. Multiple regression analysis was used to establish, via consumer's perception of the skin radiance and experts' evaluation studies, the degree to which each of the independent parameters contributes to the skin radiance perception. RESULTS: All the items of the self-assessment questionnaire explained 74% of the variation of the skin radiance. Data from experts' analysis explained 87% of the variation of skin radiance. In the two cases, skin radiance appeared to be independent of age and the presence of wrinkles. From the image analysis, we observed that the skin surface parameters explained 20% of the variation of the skin radiance expressed by experts and 24% of the variation of the skin radiance expressed by volunteers. As a result, about 80% of the variation is not explained by the instrumental data. If we combine experts' analysis and instrumental data, we obtain a mathematical model that explains 92% of the variation of the skin radiance. CONCLUSION: The questionnaire constructed from this brainstorming session allowed volunteers and experts to judge their perception of skin radiance more precisely. Video imaging appears as an interesting method to quantify visual properties of the skin and to visualize what the consumer perceives of skin radiance. However, the mathematical model proposed from the skin surface parameters analysis does not totally explain the global perception of skin radiance. In the future, it will be necessary to develop new data-processing programs to quantify subjective parameters in order to validate our mathematical model.

Development of a new sensor based on micro-electro-mechanical systems for objective in vivo measurement of the cutaneous temperature: application to foundations.

BACKGROUND/AIMS: The purpose of this work was to develop a new sensor for objective in vivo measurement of the cutaneous temperature based on micro-electro-mechanical systems (MEMS), and to compare these performances with those of a classical thermocouple. Research on this new sensor was carried out to allow the quantification of the thermal properties of the made-up skin. METHODS: Sixteen female subjects divided into two different age groups (18-35 and >50 years old) were recruited for this study. Several zones of the face and forearms were made up at random with foundations containing or not a thermoregulator raw material. The quantity of foundation applied on the skin was standardized and measurements were carried out first before make-up, and then 10 s and 5 min after make-up. The new sensor and the thermocouple were used successively on each zone. The cutaneous temperature was expressed in degrees celsius. RESULTS/CONCLUSION: The two systems are similar in terms of repeatability and reproducibility, with some differences in sensibility. The data measured by the MEMS sensor appear lower than those measured by the thermocouple. After make-up, the MEMS sensor detects a progressive increase of the temperature in time whereas the thermocouple detects a decrease. We found the same evolution on the face but in a more attenuated way. These results tend to show that the devices do not measure the same phenomenon. The thermocouple appears more sensitive to the thermal response of the made-up surface whereas the MEMS sensor appears more sensitive to the heat transfers in the interface between the skin and make-up.