Quantitative Ultrasound Super-Resolution Imaging of Intranodular and Perinodular Microvasculature for Differentiating ACR TI- RADS 4 and 5 Thyroid Nodules: A Pilot Study

Background The diagnostic accuracy of cancer detection for American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS) 4 and 5 thyroid nodules remains insufficient, leading to overdiagnosis or misdiagnosis. The heterogeneity of microvascular distribution in thyroid nodules offers a potential avenue for differentiation. The aim of this study was to evaluate the feasibility and differential diagnostic value of quantitative ultrasound super-resolution imaging (SRI) for differentiating ACR TI-RADS 4 and 5 thyroid nodules by assessing the heterogeneity of microvascular distribution between intranodular and perinodular regions. Methods This prospective study analyzed contrast-enhanced ultrasound images from 33 pathologically confirmed ACR TI-RADS 4 and 5 thyroid nodules. Quantitative microvascular parameters, including vessel diameter, vessel tortuosity, microvascular density, and fractal dimension, were measured using SRI in both intranodular and perinodular regions. Univariate and logistic regression analyses were performed to evaluate the diagnostic performance. Results In benign nodules, no significant differences were observed between intranodular and perinodular regions for all measured parameters. In malignant nodules, both perinodular microvascular density and fractal dimension were significantly higher than intranodular values. Additionally, intranodular mean tortuosity and perinodular fractal dimension in malignant nodules were significantly higher than those in benign nodules. The combination of intranodular mean tortuosity and perinodular fractal dimension achieved an area under the curve of 0.835 (95% confidence interval: 0.692–0.977) for differentiating benign from malignant thyroid nodules. Conclusion Quantitative SRI effectively characterizes differences in microvascular distribution between intranodular and perinodular regions of benign and malignant thyroid nodules. Mean tortuosity within intranodular regions and fractal dimension within perinodular regions are promising ultrasound markers for the differential diagnosis of ACR TI-RADS 4 and 5 thyroid nodules.