Anisotropic nonlinear shear elasticity quantification in ex vivo muscles

International audienceTo improve muscle pathology diagnosis or muscle characterization, nonlinear (NL) elasticity assessment could be an essential add-on to better characterize mechanical properties of soft tissues. In ultrasound shear wave elastography, nonlinear elasticity can be evaluated by using the acoustoelasticity (AE) theory. The AE theory was firstly developed and applied to quantify NL elasticity in anisotropic media such as muscles. By carrying out AE experiments on transverse isotropic (TI) Polyvinyl alcohol (PVA) phantom and ex vivo muscles, the possibility of estimating TI nonlinear elasticity in biological tissues was demonstrated. In line of this work, a mechanical testing method was used complementary to ultrasound to retrieve the third order NL elastic parameters in ex vivo muscles. The mechanical testing method provides the value of Young's modulus parallel to the muscle fibers. Thus, NL elastic coefficients were deduced using the elastodynamic equations and shear moduli retrieved by ultrasound elastography (UE). The results are very repeatable from two ex vivo porcine ilio-psoas muscles=