Biomedical subjects

Bernard Querleux

Publications and source records attributed to Bernard Querleux.

6 recordsLinked to original sources

PubMed2006

Advances in MR imaging of the skin.

MR imaging of the skin is challenging because of the small size of the structures to be visualized. By increasing the gradient amplitude and/or duration, skin layers can be visualized with a voxel size of the order of 20 microm, clearly the smallest obtained for in vivo images in a whole-body imager. Currently, the gradient strength of most commercial systems enables acquisition of such a small voxel size, and the main difficulty has thus become to achieve sufficient detection sensitivity. The signal-to-noise ratio (SNR) can be increased either by increasing the magnetic field strength or by minimizing noise with small coils; cooling copper coils or superconducting coils can enhance the SNR by a factor of 3 or more. MR imaging, because of the large number of parameters it is able to measure, can provide more than the microscopic architecture of the skin: physical parameters such as relaxation times, magnetization transfer or diffusion, and chemical parameters such as the water and fat contents or phosphorus metabolism. In spite of the amount of information they have provided to date, MR imaging and spectroscopy have had limited clinical applications, mainly because cutaneous pathologies are easily accessible to the naked eye and surgery. However, MR technologies indeed represent powerful research tools to study normal and diseased skin.

Animals↗

PubMed2004

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. Young's 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 Young's 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, Young's modulus was found to be higher in the dermis than in the hypodermis and other soft tissues.

Elasticity↗

PubMed2004

Magnetic resonance imaging and spectroscopy of skin and subcutis.

Amongst in vivo skin imaging methods, magnetic resonance (MR) imaging and spectroscopy is of high interest not only for its ability to distinguish structures at a submillimetre scale but also for its ability to describe the physiology of the different skin layers through the measurement of their intrinsic MR parameters. High spatial resolution MR imaging allows the differentiation of epidermis, dermis and hypodermis. Cutaneous appendages such as hair follicles are also clearly visible. By measuring proton relaxation times and proton density, it is possible to go a step further in the description of skin physiology in vivo through the analysis of water-macromolecular interactions within the dermis as an example. Finally, quantification of water and lipid components in healthy and diseased adipose tissue by localized spectroscopy is also described. Even if MR imaging is of little interest for dermatological diagnosis, some preliminary studies have shown interesting results for preoperative staging, postoperative follow-up, and assessment of the efficacy of new dermatological products. In healthy skin, MR imaging and spectroscopy is a very promising method for the study of chronological and photoageing effects.

Journal Article↗

PubMed2003

SkinChip, a new tool for investigating the skin surface in vivo.

BACKGROUND/AIMS: Non-invasive methods used for characterizing skin micro-relief and skin surface hydration were developed in the 1980s. Although they allowed some progress in the knowledge of skin properties, they are not completely satisfactory in many aspects. Today, new technologies are emerging that may address such issues. METHODS: We adapted the technology produced by the ST Microelectronics Company for sensing fingerprint for the measurement of skin surface properties. Accordingly, we developed acquisition software for obtaining routinely the distribution of skin surface capacitance along different body sites. Image analysis softwares were also processed for collecting both the main orientations of the micro-relief lines and their density. The average value of skin capacitance is also obtained. RESULTS: The images allow a highly precise observation of the skin topography that can be easily quantified in terms of line density and line orientation. The mean gray levels of the images appear much closely correlated to the Corneometer values. CONCLUSION: This new device appears to be a very convenient way for characterizing the properties of the skin surface. With regard to hydration, it usefully provides both the average value and the hydration chart of the investigated skin zones.

Face↗

PubMed2002

Influence of age on the wrinkling capacities of skin.

BACKGROUND: Comparisons of clinical assessment with measurement of physical parameters are rare. OBJECTIVE: To standardize the horizontal wrinkling of the skin in order to define a reference chart of the different wrinkling grades and to propose an interpretation of the clinical pattern in terms of skin layers thickness and mechanical parameters. METHODS: A device allowing reproducible wrinkling of the skin was made. The skin folds created in this way were clinically assessed on women of different ages. Measurements of the mechanical properties of the skin were carried out by using a Torquemeter. Skin layers' thicknesses were measured by using in vivo Confocal Microscopy (CM) and Ultrasound Imaging (B mode). RESULTS: Skin wrinkling grades increase versus age. Skin elasticity, extensibility and echogenicity decrease also versus age and the wrinkling grade. Wrinkling appears to be related to skin rigidification (for both stratum corneum and dermis) coupled to a certain weakening of the upper dermis (loss of echogenicity). CONCLUSION: This study points out the key role of the age-related alterations of the upper dermis in skin wrinkling capacities.

Adult↗

PubMed2002

A computational skin model: fold and wrinkle formation.

This paper presents a computational model for studying the mechanical properties of skin with aging. In particular, attention is given to the folding capacity of skin, which may be manifested as wrinkles. The simulation provides visual results demonstrating the form and density of folds under the various conditions. This can help in the consideration of proper measures for a cosmetic product for the skin.

Aging↗