In vivo quantification of the shear modulus of the human Achilles tendon during passive loading using shear wave dispersion analysis.

The shear wave velocity dispersion was analyzed in the Achilles tendon (AT) during passive dorsiflexion using a phase velocity method in order to obtain the tendon shear modulus (C 55). Based on this analysis, the aims of the present study were (i) to assess the reproducibility of the shear modulus for different ankle angles, (ii) to assess the effect of the probe locations, and (iii) to compare results with elasticity values obtained with the supersonic shear imaging (SSI) technique. The AT shear modulus (C 55) consistently increased with the ankle dorsiflexion (N = 10, p < 0.05). Furthermore, the technique showed a very good reproducibility (all standard error of the mean values <10.7 kPa and all coefficient of variation (CV) values ⩽ 0.05%). In addition, independently from the ankle dorsiflexion, the shear modulus was significantly higher in the proximal location compared to the more distal one. The shear modulus provided by SSI was always lower than C55 and the difference increased with the ankle dorsiflexion. However, shear modulus values provided by both methods were highly correlated (R = 0.84), indicating that the conventional shear wave elastography technique (SSI technique) can be used to compare tendon mechanical properties across populations. Future studies should determine the clinical relevance of the shear wave dispersion analysis, for instance in the case of tendinopathy or tendon tear.

Observation of the internal response of the kidney during compressive loading using ultrafast ultrasonography.

A protocol based on ultrafast ultrasonography was developed to study the internal response of isolated perfused human (n=3) and porcine (n=11) kidneys subjected to loading at 0.003 m/s and 0.3m/s respectively. Regional uniaxial strains were calculated based on natural target tracking. The effect of loading speed and regional differences could be statistically detected on the porcine specimens. However, despite the inhomogeneity of their anatomical structures, strains' responses appeared relatively homogeneous at 0.3m/s in both porcine and human kidneys. Failure, identified as a sudden change on the ultrasonography movie, also appeared at similar compression levels for both species (38.3% of applied strain in average for human and 35.8% of applied strain in average for porcine).