Various methods have been developed to assess the skin stiffness to assist the clinician for therapeutic monitoring or to improve diagnosis. The objective of this study was to evaluate the reliability of an acoustical characterization method based on impact analysis. This impact-based analysis method (IBAM) is based on the analysis of the variation of the force as a function of time obtained during the impact of a hammer instrumented with a force sensor on a flat-ended cylindrical punch placed in contact with a soft tissue mimicking phantom. A dedicated signal processing technique allowed us to determine an indicator Δt defined as the time difference between the impact of the hammer and the punch rebound on the hammer. The variation of Δt was correlated with the elastic properties of the sample. The sensitivities were assessed using homogeneous and bilayer structures with various thickness and rigidity, formed by soft tissues mimicking agar-based phantoms. In terms of sensitivity, IBAM can discriminate a Young's modulus difference of approximately 5 kPa with spatial sensitivity of 0.2 mm. The results open the way for the development of an easy-to-use, non-invasive and objective method that could be used in cosmetics and dermatology as a decision support system.

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