  Skeletal muscles are organized into distinct layers and exhibit anisotropic
characteristics across various scales. Assessing the arrangement of skeletal
muscles may provide valuable biomarkers for diagnosing muscle related
pathologies and evaluating the efficacy of clinical interventions. In this
study, we propose a novel ultrafast ultrasound sequence constituted of steered
pushing beams was proposed for ultrasound elastography applications in
transverse isotropic muscle. Based on the propagation of the shear wave
vertical mode, it is possible to fit the experimental results to retrieve in
the same imaging plane, the shear modulus parallel to fibers as well as the
elastic anisotropy factor. The technique was demonstrated in vitro in phantoms
and ex vivo in fusiform beef muscles. At last, the technique was applied in
vivo on fusiform muscles (biceps braachi) and mono-penate muscles
(gastrocnemius medialis) during stretching and contraction. This novel sequence
provides access to new structural and mechanical biomarkers of muscle tissue,
including the elastic anisotropy factor, within the same imaging plane.
Additionally, it enables the investigation of multiples parameters during
muscle active and passive length changes.
