3D Ultrasound based Determination of Skeletal Muscle Fascicle Orientations

Architectural parameters of skeletal muscle such as pennation angle provide valuable information on the muscle's functionality, since they can be directly related to the muscle's force generating capacities.In this paper, we introduce a 3D ultrasound based workflow for determining 3D fascicle orientations of skeletal muscles.We used a custom-designed automated motor driven 3D ultrasound scanning system for obtaining 3D ultrasound images.From these, we applied a custom-developed multiscale-vessel enhancement filter based fascicle tracking algorithm and determined muscle volume and pennation angle.We conducted trials on a phantom and on the human tibialis anterior (TA) muscle of 10 healthy subjects in plantarflexion, neutral position (corresponding to neutral standing), and one resting position in between.The results of the phantom trials showed a high accuracy with a mean absolute error of 0.92 \(\pm\) 0.59\textdegree.TA pennation angles were significantly different between all positions for the deep muscle compartment and for the superficial compartment, angles are significantly increased for neutral position compared to plantarflexion and resting position.Pennation angles were also significantly different between superficial and deep compartment.The muscle volume measurements corresponding to the 3 ankle joint angles indicates the suitability of the method for capturing 3D muscle geometry.Absolute pennation angles in our study were slightly lower than recent literature.Decreased pennation angles for plantarflexion are consistent with previous studies.The techniques presented here will enable measurement and study of muscle fascicle architecture in a variety of clinical and scientific settings, accelerating our knowledge on muscle architecture and mechanics in vivo.