Quantitative Ultrasonic Backscatter Evaluation of Elastic and Mechanical Property in a Rabbit Tendinopathy Healing Model.

Objective: This study investigates the feasibility of non-invasive ultrasound backscatter techniques for quantitative tendon characterization.

Methods: Sixty-six New Zealand white rabbits were divided into three groups: normal control group (NC group), model control group (MC group), and low-intensity pulsed ultrasound (LIPUS) treatment group (LT group). Tendinopathy models were induced in MC and LT groups, with the LT group receiving LIPUS intervention and the MC group receiving sham ultrasound therapy. The NC group underwent no treatment. Ultrasound backscatter signals were acquired in vitro and in vivo using a 3.5 MHz unfocused transducer at 1, 4, 7, 14, and 28 days post-intervention. Signals of interest (SOI) from the Achilles tendon were extracted based on in vitro monolayer tissue and in vivo multilayer tissue models. The backscatter parameters including average integrated backscatter (AIB), spectral centroid shift (SCS), frequency slope of apparent backscatter (FSAB), and frequency intercept of apparent backscatter (FIAB) were calculated and analyzed to ultrasound elastic and mechanical properties.

Results: The results revealed that backscatter parameters were strongly correlated with ultrasonic elastic properties and weakly correlated with mechanical properties, generally exhibiting negative correlations. Notably, AIB demonstrated stable characterization capability for both ultrasonic elastic and mechanical properties (in vitro: r = -0.71 for shear modulus; r = -0.43 for tensile modulus; in vivo: r = -0.70 for shear modulus; r = -0.50 for tensile modulus).

Conclusion: This study validates the use of quantitative ultrasound backscatter as a viable technique for assessing tendon properties.

Significance: ultrasound backscatter offers potential applications in tendon characterization.