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°. 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

SBC2007-176490 CHANGES IN VASCULAR VISCOELASTICITY CAUSED BY SMOOTH MUSCLE CELL TONE AND PRESSURIZATION FREQUENCY

ABSTRACT The cushioning and conduit functions of large arteries allow the body to efficiently circulate blood and perfuse organs. These functions can be characterized by quantifying the viscoelastic properties of arteries. In this study, we investigated the effects of smooth muscle cell (SMC) tone and pressurization frequency on vascular viscoelasticity using an isolated, perfused vessel test. We tested mouse carotid arteries in control, dilated (via sodium nitroprusside) and constricted (via the thromboxane receptor analogue U46619) states at 0.1, 1, 3, and 5 Hz with a pulse pressure from 90 to 120 mmHg. Dose response experiments were first performed in order to determine the optimal vasoconstrictor concentration to be used in frequency response experiments. Our results showed that energy dissipation was significantly higher and elasticity was significantly lower for vasoconstricted arteries. We also found that frequency significantly changed both energy dissipation and elasticity as the frequency was increased from 0.1 to 5 Hz. These results provide insights into the changes in vascular viscoelasticity caused by SMC tone and pressurization frequency, which have implications for vascular function in vivo

Visualizing tendon elasticity in an exvivo partial tear model

Supersonic shear imaging (SSI) is evaluated as a means of visualizing changes in regional tendon elasticity caused by partial tears in a porcine model. Thirty digital flexor tendons were cut to 25% (n=10), 50% (n=10) and 75% (n=10) of the tendon thickness along the deep surface. Tendon elasticity was mapped left of, centered on and right of the tear site before and after tearing from 0% to 2% strain. Shear wave speed increased at 1% (p \u3c 0.05) and 2% (p \u3c 0.001) strain for all regions. Deep surface shear wave speed decreased in the 25%, 50% and 75% tears (p \u3c 0.05 and p \u3c 0.001). Computational tendon tear models were also created to investigate regional changes in strain resulting from a tear. In the computational models, strain on the deep surface decreased progressively with increasing tear size. Visualization of tendon shear wave speed was achieved in normal and partially torn tendons, indicating the potential of SSI to add tendon shear wave speed to traditional morphologic assessment of partial tears, which may improve assessment of tendon health. © 2014 World Federation for Ultrasound in Medicine & Biology