An image-based mapping of significance and relevance of facial skin colour changes of females living in Thailand.

OBJECTIVE: There are methods to evaluate skin colour on defined areas over the face but no approach automatically and accurately evaluates skin colour variations on large facial areas, comparing subjects, treatments and/or time points. We propose such an image-based approach to visualize quickly the outcome of clinical studies on colour variations. METHODS: Among 54 Asian women, one group applied a vehicle twice daily, during 28 days, and the other group an anti-ageing emulsion, taking facial images at baseline and after treatment. Changes in L*a*b* values were studied on four pre-selected facial regions. We also reconstructed average facial images from which the L*a*b* parameters were extracted for every pixel, computing relevance (ΔE) and significance data. Using colour gradients, we mapped these results onto the average facial images. RESULTS: After treatment, L*a*b* parameters show no statistically relevant colour changes in the vehicle group. In the 'active' group, skin was lighter at the upper cheek and, overall, redness decreased. Relevance and significance maps confirmed no visible colour changes in the vehicle group. In the 'active' group, the mapping approach revealed colour changes and their location. Skin became lighter below the eye, cheek and forehead. It was less red below the eyes, on the cheek, jawline and forehead, and generally more yellow. CONCLUSION: Our image-based mapping approach proves to be powerful. It enables us to identify precise facial regions of relevant and statistically significant colour changes after a topical treatment, regions that would have otherwise been undetected.

OBJECTIF: Il existe des méthodes pour évaluer la couleur de la peau sur des zones pré-définies du visage mais aucune approche n'évalue de manière automatique et précise les variations de couleur de peaux sur de large régions du visage, en comparant les sujets, les traitements et/ou les temps d'analyse. Nous proposons une telle méthode basée sur l'analyse d'images pour visualiser de manière rapide les résultats des études cliniques portant sur des variations colorimétriques. MÉTHODES: Parmi 54 femmes d'origine asiatique, un premier groupe a appliqué un véhicule deux fois par jour, pendant 28 jours. Un deuxième groupe a, lui, appliqué une émulsion anti-âge. Des images de visage ont été réalisées avant et après traitement. Les variations des valeurs L*a*b* ont été étudiées sur quatre régions du visage pré-sélectionnées. Nous avons également reconstruit des images de visages moyens pour lesquelles les paramètres L*a*b* ont été extraits pour chaque pixel. Pour ces mêmes pixels, les valeurs de pertinence (delta E) et significativité ont été calculées. A l'aide d'un gradient de couleur, nous avons représenté ces résultats sur les images de visages moyens. RÉSULTATS: Après traitement, les paramètres L*a*b* n'ont montré aucun résultat significativement pertinent pour le groupe ayant appliqué le véhicule. Pour le groupe "actif", la peau est devenue plus claire sur la partie supérieure de la joue et globalement moins rouge. Les cartographies de pertinence et de significativité ont confirmée l'absence de variation colorimétrique sur le groupe véhicule. Sur le groupe "actif", l'approche par cartographie a révélé les changements de couleurs et leur localisation. La peau est devenue plus claire sous les yeux, sur les joue et le front. Le dessous des yeux, les joues, la mâchoire et le front sont devenues moins rouges et généralement plus jaunes. CONCLUSION: Notre approche de cartographie basé sur l'analyse d'images s'est montrée pertinente. Elle nous permet d'identifier de manière précise les régions du visage sur lesquelles des changements pertinents et significatifs de couleur ont eu lieu après l'application d'un traitement topique. Ces régions n'auraient pas été détectées sans cette technique.

SpectraCam® : A new polarized hyperspectral imaging system for repeatable and reproducible in vivo skin quantification of melanin, total hemoglobin, and oxygen saturation.

BACKGROUND: An accurate way to determine skin pigmentation is to acquire the spectral reflectance of a skin sample and to quantify chromophores by reverse calculation from physical models of light propagation. Therefore, we tested a new hyperspectral imaging device and software suite, the SpectraCam® system, and evaluated its accuracy to quantify skin chromophores. METHODS: Validation of the SpectraCam® system was performed by, firstly, comparing the known and the acquired reflectance spectra of color phantoms. Repeatability and reproducibility were then evaluated by two operators who performed acquisitions at different time points and compared the acquired reflectance spectra. The specificity of the system was tested by quantitative analysis of single chromophore variation models: lentigo and pressure relief. Finally, we tested the ability of the SpectraCam® system to detect variations in chromophore in the eye region due to the daily application of a new anti-dark circle cosmetic product. RESULTS: The SpectraCam® system faithfully acquires the reflectance spectra of color phantoms (r2 >0.90). The skin reflectance spectra acquired by different operators at different times are highly repeatable (r2 >0.94) and reproducible (r2 >0.99). The SpectraCam® system can also produce qualitative maps that reveal local variations in skin chromophore or underlying structures such as blood vessels. The system is precise enough to detect melanin variation in lentigo or total hemoglobin and oxygen saturation variations upon pressure relief. It is also sensitive enough to detect a decrease in melanin in the eye region due to the application of an anti-dark circle cosmetic product. CONCLUSION: The SpectraCam® system proves to be rapid and produces high-resolution data encompassing a large field of view. It is a robust hyperspectral imaging system that quantifies melanin, total hemoglobin, and oxygen saturation and is well adapted to cosmetic research.

Novel approaches to characterize age-related remodelling of the dermal-epidermal junction in 2D, 3D and in vivo.

BACKGROUND/PURPOSE: The dermal-epidermal junction (DEJ) forms epidermal protrusions down into the dermis (rete ridges) and dermal projections up into the epidermis (dermal papillae). Usually visualized in two-dimensions (2D), our knowledge of how the DEJ changes with ageing is limited. We aimed to characterize how this structure exists in 3D and changes with age. METHODS: Photoprotected and photoexposed skin were imaged using reflectance confocal microscopy (RCM) in young and aged individuals. Biopsies of the imaged areas were processed for histological sectioning and for imaging using micro-computed X-ray tomography (microCT). RESULTS: Images obtained from RCM and microCT were used to 3D reconstruct the DEJ. DEJ heights obtained from microCT images showed strong correlation with histology-measured heights. We proposed a novel definition of rete ridges (RRm ) and dermal papillae (DPm ), which allowed easier automated measurement of reduced DPm and RRm volumes in aged skin from microCT reconstructions. An algorithm to map DPm connectivity showed reduced lengths of DPm branches with age. CONCLUSION: Three-dimensional images illustrated the complex topography of the DEJ and highlighted the distinct morphology of dermal papillae compared with rete ridges, which is not evident when evaluating 2D sections. Ex vivo imaging was more successful in differentiating DEJ architecture with respect to age.

A novel continuous colour mapping approach for visualization of facial skin hydration and transepidermal water loss for four ethnic groups.

OBJECTIVES: The aim of this exploratory study was to develop a novel colour mapping approach to visualize and interpret the complexity of facial skin hydration and barrier properties of four ethnic groups (Caucasians, Indians, Chinese and Black Africans) living in Pretoria, South Africa. METHODS: We measured transepidermal water loss (TEWL) and skin capacitance on 30 pre-defined sites on the forehead, cheek, jaw and eye areas of sixteen women (four per ethnic group) and took digital images of their faces. Continuous colour maps were generated by interpolating between each measured value and superimposing the values on the digital images. RESULTS: The complexity of facial skin hydration and skin barrier properties is revealed by these measurements and visualized by the continuous colour maps of the digital images. Overall, the Caucasian subjects had the better barrier properties followed by the Black African subjects, Chinese subjects and Indian subjects. Nevertheless, the two more darkly pigmented ethnic groups had superior skin hydration properties. Subtle differences were seen when examining the different facial sites. CONCLUSIONS: There exists remarkable skin capacitance and TEWL gradients within short distances on selected areas of the face. These gradients are distinctive in the different ethnic groups. In contrast to other reports, we found that darkly pigmented skin does not always have a superior barrier function and differences in skin hydration values are complex on the different parts of the face among the different ethnic groups.