Analyses of muscle-tendon junction several methods

Ultrasound imaging is used to measure the muscle–tendon junction (MTJ) to investigate the mechanical properties of the tendon and the interaction of the muscle–tendon unit in vivo.Although the MTJ can be observed clearly in the resting state, accurate tracking of the MTJ is difficult during muscle contractions due to changes in its morphology. We devised a novel method using an algorithm that extracts and tracks multiple feature points in ultrasound images to automatically measure the MTJ that moves with muscle contraction. We then evaluated the usefulness of this method experimentally. Tests were conducted on 20 participants performing isometric maximal contractions, and ultrasound echo images of the gastrocnemius and Achilles tendon junctions were recorded. MTJ excursion was calculated using the developed multiple feature points algorithm and two conventional methods (multi-updating template-matching and modified Lucas–Kanade [LK]) of automatic analysis. The root mean square error (RMSE) was used to compare the obtained results. The intraclass correlation coefficient (ICC) was used to evaluate repeatability among examiners. RMSE was 1.57±0.62 for the proposed algorithm and 2.18±0.89, 1.84±1.13 for the conventional methods. Thus, the proposed algorithm had a smaller error. Furthermore, the ICC values were 0.96, 0.40, and 0.86 for the proposed algorithm, multi-updating template-matching, and the modified LK method, respectively. When tracking an MTJ excursion that flexibly changes its shape, the use of multiple feature points provides robust results and achieves tracking that approximates the manual analysis results.