Measurement of tendon velocities using vector tissue Doppler imaging and curved M-mode in patients with cerebral palsy

We have developed two ultrasound-based methods, vector tissue Doppler imaging (vTDI) and curved M-mode (cMM), to directly quantify the magnitude of muscle and tendon velocities. The goal of this study was to investigate the repeatability of the vTDI and cMM system in measuring tendon velocities in vivo and cross validate between these two independent methods. We performed a preliminary study on children with cerebral palsy (CP) who have foot drop (inadequate dorsiflexion during swing phase of gait), and were undergoing treatment using a functional electrical stimulation device. While vTDI estimated peak instantaneous velocity during dorsiflexion, cMM estimated displacement, from which a mean dorsiflexion velocity could be derived. The peak velocities from vTDI and mean velocity from cMM showed strong correlations with peak and mean joint angle velocities from 3D motion capture (R² =0.81 and 0.78, respectively) for all four cases over multiple trials, and the vTDI estimates were consistent with the cMM estimates. These preliminary results demonstrate that direct ultrasonic measurements of muscle and tendon velocities may be used as clinical outcome measures and for studying patients with gait related disorders like CP.