In vivo estimation of flexor digitorum superficialis tendon displacement with speckle tracking on 2-D ultrasound images using Laplacian, Gaussian and Rayleigh techniques.

Abstract This study applies 2-D speckle tracking using B-scan ultrasound imaging to estimate the instantaneous and total displacement of the middle flexor digitorum superficialis (FDS) tendon proximal to the wrist. This is achieved by performing the study with human patients, during regular carpal tunnel surgeries. B-Scan images were collected with a 12-MHz transducer placed proximal to the wrist, while a video microscope simultaneously imaged the exposed flexor tendons in the palm as a reference for validation. The accuracy of the proposed speckle-based tracking method is compared using log-compressed Rayleigh (Fisher-Tippet)-, Gaussian (sum of squared differences)- and Laplacian (sum of absolute differences)-based statistics as similarity measures. Overall, tracking was successful and the Rayleigh technique performed better than the Laplacian or Gaussian technique. One goal of this research was to non-invasively monitor FDS tendon displacement in the wrist for the purposes of controlling a prosthetic device. An additional goal was to obtain pre- and post-operative clinical information.