Browsing by Author "Eranki, Avinash"

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    A Novel Application of Musculoskeletal Ultrasound Imaging
    (Journal of Visualized Experiments, 2013-09) Eranki, Avinash; Cortes, Nelson; Ferenček3, Zrinka Gregurić; Siddhartha, Sikdar
    Ultrasound is an attractive modality for imaging muscle and tendon motion during dynamic tasks and can provide a complementary methodological approach for biomechanical studies in a clinical or laboratory setting. Towards this goal, methods for quantification of muscle kinematics from ultrasound imagery are being developed based on image processing. The temporal resolution of these methods is typically not sufficient for highly dynamic tasks, such as drop-landing. We propose a new approach that utilizes a Doppler method for quantifying muscle kinematics. We have developed a novel vector tissue Doppler imaging (vTDI) technique that can be used to measure musculoskeletal contraction velocity, strain and strain rate with sub-millisecond temporal resolution during dynamic activities using ultrasound. The goal of this preliminary study was to investigate the repeatability and potential applicability of the vTDI technique in measuring musculoskeletal velocities during a drop-landing task, in healthy subjects. The vTDI measurements can be performed concurrently with other biomechanical techniques, such as 3D motion capture for joint kinematics and kinetics, electromyography for timing of muscle activation and force plates for ground reaction force. Integration of these complementary techniques could lead to a better understanding of dynamic muscle function and dysfunction underlying the pathogenesis and pathophysiology of musculoskeletal disorders.
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    Measurement of Musculoskeletal Motion Using Vector Tissue Doppler Imaging
    (2010-11-10) Eranki, Avinash; Eranki, Avinash; Sikdar, Siddhartha
    The goal of this project is to develop, characterize and validate vector tissue Doppler imaging (vTDI) to measure dynamic musculoskeletal motion. We have developed a vector tissue Doppler imaging system using a clinical ultrasound scanner with a research interface. This system estimates motion in two or more independent directions using multiple electronicallycontrolled transmitters and receivers oriented in different directions. The vector tissue Doppler method combines the multiple velocity estimates producing a single velocity vector with magnitude and direction. We characterized this system in vitro by changing four parameters, namely, beam steering angle, depth of transmit focus, angle of velocity vector and the depth of the scatterer relative to the beam overlap region. Our results show that changing these parameters have minimal effect on the velocity and angle estimates, and robust velocity vector estimates can be obtained under a variety of conditions. The mean velocity error was less than 6% of the maximum detectable velocity. We then performed some preliminary in vivo experiments to measure the velocity of the rectus femoris muscle group during a tendon tap in normal volunteers. Our goal was to investigate whether the muscle elongation velocities during a brisk tendon tap fall within the normal range of velocities that are expected due to rapid stretch of limb segments. We found that the equivalent velocities elicited during standard patellar tendon jerk test are within the range of velocities (3.26 rad s-1 to 8.23 rad s-1) encountered in typical everyday activities, but the angular accelerations substantially exceeded the accelerations encountered in everyday activities (191.8 rad s-2 to 4038.6 rad s-2). Our study provides the experimental evidence to support the non- physiological character of the tendon taps which is used during standard neurological tests. We also investigated the feasibility of using vector tissue Doppler velocity estimates as a reliable clinical outcome measure in children with cerebral palsy (CP) and who have foot drop, or inadequate ankle dorsiflexion during the swing phase of gait. We measured the tibialis anterior tendon contraction velocities during ankle dorsiflexion. Our preliminary results from this study show that tendon velocities estimated using vTDI have a strong linear correlation with the joint angular velocity estimated using a conventional 3D motion capture system. We observed a peak tendon velocity of 5.42±1.01 cm/s during dorsiflexion and a peak velocity of 8.02±2.33 cm/s during the passive relaxation phase of movement. Our preliminary studies demonstrate that vector Doppler may be used as clinical outcome measures and for studying efficiency of movement control. In the future, vector tissue Doppler imaging (vTDI) may be used to better understand gait disorders in patients suffering from cerebral palsy, spinal cord and brain trauma and other neuromuscular disorders.