High-Frequency Quantitative Ultrasound Parameters Correlate With Microstructural Properties in a Murine Collagenase...

High-frequency quantitative ultrasound (QUS) offers a promising approach to characterize soft tissue microstructure ex vivo. In this study, we evaluated its ability to detect histological tendon changes in a murine model of patellar tendinopathy. Collagenase was injected into the patellar tendon of C57BL/6 J mice to induce tendinopathy. Tendons were scanned ex vivo using a 60-MHz transducer to acquire radiofrequency (RF) ultrasound echo data. QUS parameters based on envelope statistics and backscatter coefficient measurements were computed from the RF data. Additionally, tendon thickness was measured from the B-mode images. QUS parameters were compared between control and collagenase-injected groups. Histological sections were evaluated using a modified Movin score. Significant differences were observed in QUS parameters effective scatterer diameter (ESD), the Homodyned-K parameter $\alpha$ , and thickness between control and collagenase-injected groups (p < 0.05 for all). ESD and thickness correlated with histological scores (R = 0.50, p < 0.001 for both), and receiver operating characteristic analyses showed high classification accuracy (AUC = 0.82-0.89). These findings indicate that QUS parameters are sensitive to pathological alterations in tendon microstructure and may serve as surrogate markers of structural integrity. As a rapid, cost-effective, and portable imaging modality, QUS holds strong potential for longitudinal monitoring of tendinopathy and evaluating treatment response in both animal models and clinical settings. Statement of Clinical Significance: QUS parameters detected tendon microstructural changes, indicating potential for non-invasive longitudinal monitoring, although limited here to post-mortem imaging.