Strain measurements of rabbit Achilles tendons by ultrasound.

Axial components of tendons' transverse strain fields were successfully measured in vitro by ultrasound. Achilles tendons of New Zealand white rabbits were used. Tendon inflammation was simulated by artificially inducing ischemia. Strain measurements were also correlated with conventional B-mode sonograms and histological micrographs. Results showed that strain measurements had reasonable agreement with histological examinations and provided better tissue differentiation than conventional B-mode imaging. For a given tendon, the strain values corresponding to different tissue layers were easily differentiated with an elastographic contrast-to-noise ratio ranging from 17 to 43 dB. Such differences, however, were not always present in the sonograms. Therefore, ultrasonic strain imaging may be a useful tool for assessing tendon disorders during the rehabilitation process.