Influence of pennation angle on measurement of shear wave elastography: in vivo observation of shear wave propagation in human pennate muscle

Abstract

Objective: To examine the influence of pennation angle on measurement of shear wave elastography, this study utilised the propagation view mode that can reveal shear wave propagation in human pennate muscle in vivo. Approach: The validity of the propagation view mode was qualitatively confirmed by observation of shear wave propagation in tissue-mimicking phantoms. Shear wave velocity of the medial gastrocnemius (MG) was evaluated in 15 healthy males. By changing the placement of the ultrasound probe on the skin surface, shear wave propagation in the MG was changed: shear waves propagated along the MG fascicles (horizontal condition) and across the fascicles (oblique condition). Main results: It was observed that shear wave propagation became faster when shear waves passed through stiffer parts of the phantoms and perimysium of the MG, which is concordant with the basic principle of shear wave elastography. Shear wave velocity in the horizontal condition (2.69 ± 0.71 m s−1) was significantly higher than that in the oblique condition (2.61 ± 0.73 m s−1) (p < 0.001), but the effect size was small (Cohen’s d = 0.11). Significance: Ultrasound shear wave elastography can evaluate tissue elasticity of pennate muscles along the fascicle direction, even if shear waves propagate across the obliquely arranged fascicles.