Thérèse Baldeweck

Assessment of elastic parameters of human skin using dynamic elastography

Sonoelastography and transient elastography are two ultrasound-based techniques that facilitate noninvasive characterization of the viscoelastic properties of soft tissues by investigating their response to shear mechanical excitation. Youngs modulus is the principle assessment parameter. Because it defines local tissue stiffness, it is of major interest for the medical imaging and cosmetic industries as it could replace subjective palpation by yielding local, quantitative information. In this paper, we describe a new high-resolution device capable of measuring local Youngs modulus in very thin layers (1-5 mm) and devoted to the in vivo evaluation of the elastic properties of human skin. It uses an ultrasonic probe (50 MHz) for tracking the displacements induced by a 300 Hz shear wave generated by a ring surrounding the transducer. The displacements are measured using a conventional cross-correlation technique between successive ultrasonic back-scattered echoes. First, this noninvasive technique has been experimentally proven to be accurate for investigating elasticity in different skin-mimicking phantoms. Second, data were acquired in vivo on human forearms. As expected, Youngs modulus was found to be higher in the dermis than in the hypodermis and other soft tissues.

Influence of age on the wrinkling capacities of skin

Background: Comparisons of clinical assessment with measurement of physical parameters are rare.

Skin from various ethnic origins and aging: an in vivo cross-sectional multimodality imaging study

Background: Ethnic differences in skin structural features have not been thoroughly investigated, and the few reported studies are contradictory. Thus, we have carried out a set of in vivo measurements on the skin of about 400 volunteers from various ethnic origins living in the same environment.

Automatic 3D segmentation of multiphoton images: a key step for the quantification of human skin.

Multiphoton microscopy has emerged in the past decade as a useful noninvasive imaging technique for in vivo human skin characterization. However, it has not been used until now in evaluation clinical trials, mainly because of the lack of specific image processing tools that would allow the investigator to extract pertinent quantitative three‐dimensional (3D) information from the different skin components.

Segmentation of elongated objects using attribute profiles and area stability: Application to melanocyte segmentation in engineered skin

In this paper, a method to segment elongated objects is proposed. It is based on attribute profiles and area stability. Images are represented as component trees using a threshold decomposition. Then, some attributes are computed on each node of the tree. Finally, the attribute profile is analyzed to identify important events useful for segmentation tasks. In this work, a new attribute, combining geodesic elongation and area stability is defined. This methodology is successfully applied to the segmentation of cells in multiphoton fluorescence microscopy images of engineered skin. Quantitative results are provided, demonstrating the performance and robustness of the new attribute. A comparison with MSER is also given.

In vivo multiphoton microscopy associated to 3D image processing for human skin characterization

Multiphoton microscopy has emerged in the past decade as a promising non-invasive skin imaging technique. The aim of this study was to assess whether multiphoton microscopy coupled to specific 3D image processing tools could provide new insights into the organization of different skin components and their age-related changes. For that purpose, we performed a clinical trial on 15 young and 15 aged human female volunteers on the ventral and dorsal side of the forearm using the DermaInspectR medical imaging device. We visualized the skin by taking advantage of intrinsic multiphoton signals from cells, elastic and collagen fibers. We also developed 3D image processing algorithms adapted to in vivo multiphoton images of human skin in order to extract quantitative parameters in each layer of the skin (epidermis and superficial dermis). The results show that in vivo multiphoton microscopy is able to evidence several skin alterations due to skin aging: morphological changes in the epidermis and modifications in the quantity and organization of the collagen and elastic fibers network. In conclusion, the association of multiphoton microscopy with specific image processing allows the three-dimensional organization of skin components to be visualized and quantified thus providing a powerful tool for cosmetic and dermatological investigations.

New general features based on superpixels for image segmentation learning

Segmenting an image is usually one of the major and most challenging steps in the pipeline of biomedical image analysis. One classical and promising approach is to consider segmentation as a classification task, where the aim is to assign to each pixel the label of the objects it belongs to. Pixels are therefore described by a vector of features, where each feature is calculated on the pixel itself or, more frequently, on a sliding window centered on the pixel. In this work, we propose to replace the sliding window by superpixels, i.e. regions which adapt to the image content. We call the resulting features SAF (Superpixel Adaptive Feature). Their contribution is highlighted on a biomedical database of melanocytes images. Qualitative and quantitative analyses show that they are better suited for segmentation purposes than the sliding window approach.

Non‐invasive short‐term assessment of retinoids effects on human skin in vivo using multiphoton microscopy

The occlusive patch test developed for assessing topical retinoids activity in human skin has been extended as a short‐term screening protocol for anti‐ageing agents. In this model, biopsies are performed at the end of the occlusion period for morphological and immuno‐histochemistry analysis. Multiphoton microscopy is a recent non‐invasive imaging technique that combined with image processing tools allows the in vivo quantification of human skin modifications.

Multiphoton FLIM in cosmetic clinical research

There is an increasing need in cosmetic clinical research for non-invasive, high content, skin imaging techniques offering the possibility on the one hand, to avoid performing invasive biopsies, and on the other hand, to supply a maximum of information on the skin state throughout a study, especially before, during and after product application. Multiphoton microscopy is one of these techniques compatible with in vivo human skin investigations, allowing human skin three-dimensional (3D) structure to be characterized with sub-µm resolution. In association with fluores-cence lifetime imaging (FLIM) and specific 3D-image processing, one can extract several quantitative parameters characterizing skin constituents in terms of morphology, density and organization. Various intracellular and extracellular constituents present specific endogenous signals enabling a non-invasive visualization of the 3D structure of epidermal and superficial dermal layers. Multiphoton FLIM applications in the cosmetic field range from knowledge to evaluation studies. Knowledge studies aim to acquire a better knowledge of skin differences appearing with aging, solar exposure or between the different skin phototypes. Evaluation studies deal with the efficacy of cosmetic anti-aging or whitening ingredients. The goal of this chapter is not to give a literature review of multiphoton FLIM applications in cosmetic clinical research, but rather to acquaint the reader with the quantitative 3D information afforded by multi-photon FLIM imaging of human skin and its interest in cosmetic clinical research.