Value of Intratumoral and Peritumoral Ultrasound Radiomics Nomogram for Differential Diagnosis of C‐TIRADS 4 Thyroid Nodules

OBJECTIVE: The Chinese Thyroid Imaging Reporting and Data System (C-TIRADS) 4 thyroid nodules (TNs) have intricate sonographic features that potentially lead to overdiagnosis or misdiagnosis. This study aimed to improve the precision of differentiating C-TIRADS 4 TNs using radiomic nomograms that include both intratumoral and peritumoral features. METHODS: A total of 337 patients with C-TIRADS 4 thyroid nodules confirmed by pathology or FNAB were retrospectively enrolled and randomly divided into a training cohort (n = 269) and a validation cohort (n = 68) at a ratio of 8:2. Radiomics features were extracted from intratumoral and peritumoral (1-3 mm) regions on B-mode ultrasound images. Feature stability was assessed using intraclass and intraclass correlation coefficients (ICC). Key features were selected through a sequential process involving the Mann-Whitney U test, recursive feature elimination (RFE), and least absolute shrinkage and selection operator (LASSO) regression, followed by calculation of the radiomics score (Rad-score). Independent predictors were identified by univariate and multivariate logistic regression. Three models were constructed: a clinical and ultrasound model (Model 1), a radiomics model (Model 2), and a combined nomogram integrating both (Model 3). Model performance and clinical utility were evaluated using receiver operating characteristic curves, calibration curves, and decision curve analysis (DCA). RESULTS: Multivariate analysis showed that age, margin, echogenic foci, and the intratumoral and peritumoral 1 mm Rad-score were independent predictors for the benign or malignant nature of C-TIRADS 4 nodules (p < 0.05). The combined nomogram (Model 3) achieved an area under the curve (AUC) of 0.852 (95% CI: 0.804-0.892) in the training cohort, significantly higher than that of Model 1 (AUC = 0.737) and Model 2 (AUC = 0.784) (p < 0.05). In the validation cohort, Model 3 yielded an AUC of 0.916 (95% CI: 0.851-0.980), outperforming Model 1 (AUC = 0.766) and Model 2 (AUC = 0.807) (both p < 0.05). The calibration curve of the nomogram showed good agreement with the ideal curve (Hosmer-Lemeshow test p > 0.05), and DCA indicated that it provided the greatest clinical net benefit. CONCLUSION: The nomogram integrating clinical characteristics, ultrasound characteristics, and intratumoral and peritumoral 1 mm Rad-score can distinguish benign from malignant C-TIRADS 4 TNs, with superior diagnostic performance compared to single-modality models. It may serve as a non-invasive and reliable tool to reduce unnecessary FNAB rates.