Bilayer Stiffness Identification of Soft Tissues by Suction

Abstract

In vivo mechanical characterisation of biological soft tissue is challenging, even under moderate quasi-static loading. Clinical application of suction-based methods is hindered by usual assumptions of tissues homogeneity and/or time-consuming acquisitions/postprocessing Provide practical and unexpensive suction-based mechanical characterisation of soft tissues considered as bilayered structures. Inverse identification of the bilayers’ Young’s moduli should be performed in almost real-time. An original suction system is proposed based on volume measurements. Cyclic partial vacuum is applied under small deformation using suction cups of aperture diameters ranging from 4 to 30 mm. An inverse methodology provides both bilayer elastic stiffnesses, and optionally the upper layer thickness, based on the interpolation of an off-line finite element database. The setup is validated on silicone bilayer phantoms, then tested in vivo on the abdomen skin of one healthy volunteer. On bilayer silicone phantoms, Young’s moduli identified by suction or uniaxial tension presented a relative difference lower than 10 % (upper layer thickness of 3 mm). Preliminary tests on in vivo abdomen tissue provided skin and underlying adipose tissue Young’s Moduli at 54 kPa and 4.8 kPa respectively. Inverse identification process was performed in less than one minute. This approach is promising to evaluate elastic moduli in vivo at small strain of bilayered tissues.