Direct in plane elastic anisotropy factor quantification with inclined push beams in muscles

Ultrasound based elastography (UE) methods have recently been developed to map the muscle stiffness by examining the shear wave generated by acoustic radiation force. However, one of their major challenges is to account for muscle anisotropy. Different methods have been introduced to perform the 3D elasticity measurements that allows to consider the muscle as transverse isotropic material, the simplest case of anisotropic medium. Otherwise, due to the cumbersome processing, UE is still limited with a linear probe, that does not allow to display the elastic map in 3D. One of the solutions for this question is to rotate probe to acquire the image in different angles. Nonetheless, that can only reveal elastic information in the imaging plan, as the shear wave propagation is only captured in transverse direction (along x axis). The method that we are suggesting here can give muscle shear modulus in vertical direction (along z axis) by inclining the push beam and projecting the displacement of the shear wave in the vertical and horizontal axes (z and x). Being followed by a smart reconstruction, the method allows to retrieve the two shear moduli (µ) maps along the fibre's axis and its perpendicular axis. The anisotropy factor can thus be deduced, that allows to evaluate the anisotropic effects on muscular phenomena. This method can be implemented to provide a new biomarker for muscular pathologies such as Duchenne muscular dystrophy as well as functional assessment of sports movements.