Stephane Diridollou

In vivo model of the mechanical properties of the human skin under suction

Background/aims: A new method for the in vivo characterization of the mechanical properties of skin has been developed. This comprises a suction chamber and an ultrasound device to measure both the vertical displacement of the skins surface, and the skins thickness.

Skin topography measurement by interference fringe projection: a technical validation.

Background/aims: The quantitative analysis of skin topography is frequently used in cosmetology to evaluate the efficacy of hydrating or anti‐wrinkle creams (micro‐topography studies) or creams for slimming or to alleviate stretch marks (macro‐topography studies). Numerous methods involving the three‐dimensional (3‐D) reconstruction of the topography from silicone replicas have been developed. Some of the main techniques applied include optical profilometry based on the reflection of oblique lighting or on transparency, and profilometry by laser focusing or triangulation.

Comparative study of the hydration of the stratum corneum between four ethnic groups: influence of age

Background  Several recent overviews have reported that significant work remains to be performed to understand and quantify the ethnic differences in skin properties.

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.

The effect of age on skin color and color heterogeneity in four ethnic groups

Background: Few comparative data are available on age‐related changes in skin color among different ethnic groups. The aim of the study was to measure and analyze the skin color and color heterogeneity in four different ethnic groups living in the same local environment and to determine the effects of age on these skin color characteristics.

Spatial variation of acoustic parameters in human skin: an in vitro study between 22 and 45 MHz

This study of spatial variance of acoustic parameters was performed on eight nonfrozen samples of female abdominal skin (women 46.5 +/- 12.2 years old), obtained during plastic surgery. Intra- and interindividual variations are discussed on the basis of estimations of three acoustic parameters (slope of attenuation- beta; integrated attenuation coefficient- IAC; integrated backscattering coefficient- IBC) and one texture parameter (based on two estimators of effective density of scatterers: alpha(2) and alpha(1/2)) as a function of surface area and depth of acquisition in the frequency range 22 to 45 MHz. Values of intraindividual variations varied from 7.1% for IAC to 23.2% for IBC, and significantly decreased at a ratio between 1.2 to 2.3 when the acquisition surface area was increased from 4 mm(2) to 1 cm(2). Interindividual variations were higher than intraindividual variations, and varied from 14.2% for alpha(1/2) to 51% for IBC. The mean values (+/- SD) for all specimens combined, estimated with a large number of independent radiofrequency (RF) lines (400) and for a surface area of exploration of 4 cm(2), were 1.06 +/- 0.17 dB cm(-1) MHz(-1) for beta, 135 +/- 37 dB cm(-1) for IAC, (3.7 +/- 1.9) x 10(-2) cm(-1) sr(-1) for IBC, 1.40 +/- 0.17 scatterers/resolution cell for alpha(2) and 1.32 +/- 0.27 scatterers/resolution cell for alpha(1/2). Finally, attenuation micro(f) and backscattering coefficient sigma(b)(f) were compared to published results for the same parameters measured in human skin.

The influence of African-American hair's curl pattern on its mechanical properties.

Numerous studies have described the physical differences in hair from people of different ethnicities, 1–16 yet little is known about intraracial curl pattern differences. It is readily observable that virgin hair from people of African descent can have varying degrees of curl (Fig. 1), and it has often been hypothesized that these geometric differences can influence the mechanical properties of hair. This has prompted systematic research to determine the physical properties of hair that has various degrees of curl. This paper describes the physical differences found in a comparison of several samples of African-American hair with different degrees of curl.

Potential of a high‐frequency correlation method to study skin blood flow

Background/aims: The vast number of existing dedicated techniques proves that skin blood flow estimation is an unsolved problem. Specificities of cutaneous vascularization (very low blood velocity, noisy environment, complexity of the vascularization architecture) result in the unsuitability of conventional ultrasonic Doppler techniques (long acquisition time, low spatial resolution). The object here was to present a high‐frequency time‐domain correlation method. In particular, the difficulties of adaptating this type of measurement (data processing, hardware problem) are pointed out.