Transient elastography (TE) is a technique used to quantify Young's Modulus (E) by estimating shear wave velocity in homogenous tissues. This technique has been successfully integrated in the Fibroscan ® device to assess fibrosis stages in liver but has never been validated in the monitoring of skin fibrosis diseases. A specific device based on high-frequency transient elastography (HF-TE) is used to evaluate its performance in case of chronic venous disorder (CVD) diagnosis. E, dermis thickness (DT) and a new parameter, P E - DT , based on a logistic regression model using both E and DT are measured in the dermis of 48 healthy and 48 CVD patients. The discriminant capacity of E, DT and Pe-dt parameters is evaluated with a receiver operating characteristic (ROC) analysis.

Interest in elasticity estimation for thin layers is increasing because of the various potential applications, including dermatology and cosmetology. In this context, we propose a dedicated elastographic system using 1-D high-frequency transient elastography (HF-TE) to estimate the 1-D Young's modulus through the dermis and hypodermis, which are the two human skin layers of interest in this study. An experimental validation of the HF-TE method was first carried out on two homogeneous tissue-mimicking hard and soft phantoms. The Young's modulus values obtained in these phantoms were compared with those obtained by two complementary shear wave propagation techniques: shear wave-induced resonance elastography (SWIRE) and supersonic shear imaging (SSI). A third two-layer thin phantom, with mechanical properties similar to those of skin, was used to validate the ability of HF-TE to distinguish layers and measure elasticity. Finally, preliminary in vivo experiments conducted on forearm and cheek skin revealed the promising performance of HF-TE in measuring elasticity in the dermis and hypodermis.

Elastographic methods are used to characterize mechanical properties of soft tissues. Phantom materials mimicking tissues are commonly used to evaluate performances of elastographic methods. In this context, two kinds of materials were used and, for each kind, a set of phantoms was manufactured in our laboratory with a large range of variation of their Young's modulus (E). Their modulus have been measured with three elastographic techniques based on the generation and measurement of shear waves (Shear Wave Induced Resonance Elastography, Transient Elastography and Supersonic Shear Imaging) in order to compare median and dispersion of the measured E values.

In order to estimate the shear wave velocity in transient elastography (TE), we proposed an algorithm based on detection of neighboring local minima maxima (MM) of successive RF signals to estimate displacement field. This algorithm is performed since the US acquisition is ultrafast (e.g. PRF 80 kHz) to obtain a local delay inferior than half-period of the RF signal. In this case we reached a high spatial resolution in the elastogram (SR = quarter of wavelength (λ)) with a good SNRe which is helpful for thin media (few mm) investigation such as the skin. Furthermore, the elastogram quality is linked only to acoustic SNR and anymore to windowing parameters.