Reproducibility of shear wave elastography measuresof the Achilles tendon

Objective To assess the reproducibility of shear wave elastography (SWE) measures in the Achilles tendon (AT) in vivo. Materials and methods Shear wave velocity (SWV) of 14 healthy volunteers [7 males, 7 females; mean age 26.5 +/- 3.8 years, mean height 171.6 +/- 10.9 cm, mean Victorian Institute of Sports Assessment Achilles questionnaire (VISA-A) score 99.4 +/- 1.2] was measured with the foot relaxed and fixed at 90 degrees. Data were collected over five consecutive measures and 5 consecutive days. Results Mean SWV values ranged from 7.91 m/s-9.56 m/s +/- 0.27-0.50 m/s. Coefficient of variation (CV), correlations and intra-class correlation coefficient (ICC) scores ranged from 2.9%-6.3%, 0.4-0.7 and 0.54-0.85 respectively. No significant differences were noted for longitudinal or transverse data with respect to protocol or time and no significant differences were noted for foot position in transverse data. Significant differences in SWV values were noted between foot positions for longitudinal scanning (p = < 0.05), with a relaxed foot position providing SWV values on average 0.47 m/s faster than a fixed position. Increased reproducibility was obtained with the foot relaxed. ICC between operators was 0.70 for transverse and 0.80 for longitudinal scanning. Conclusions Reproducible SWE measures were obtained over a 1-h period as well as a period of 5 consecutive days with more reliable measures obtained from a longitudinal plane using a relaxed foot position. SWE also has a high level of agreement between operators making SWE a reproducible technique for quantitatively assessing the mechanical properties of the human AT in vivo.