Not yet reviewed by Pith; the record is open.

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.