Comparative Analysis of ACR TI-RADS and K-TIRADS: Inter-System Agreement and Diagnostic Performance Using a Single Study Cohort.

Purpose: To evaluate the inter-system agreement and diagnostic performance of experienced readers using two Thyroid Imaging Reporting and Data Systems (TI-RADS). Materials and Methods: A total of 481 thyroid US images were collected retrospectively. Four experienced radiologists independently reviewed the images and documented the US features and final assessments based on the Korean TI-RADS (K-TIRADS). The final American College of Radiology (ACR) TI-RADS score was calculated using individual US feature scores. The final assessments from both TI-RADS systems were used to evaluate inter-reader and inter-system agreement. The diagnostic performance metrics, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and unnecessary biopsy rate, were calculated and compared. Results: Among the 481 US images, 157 were benign, 184 were malignant, and 140 were negative images. In the final assessment, substantial agreement was observed between the two TI-RADS systems (κ = 0.61) for all four readers. The mean AUC did not differ significantly between ACR TI-RADS and K-TIRADS ( Conclusion: Substantial agreement was observed between the final assessments of ACR TI-RADS and K-TIRADS. The mean AUC did not differ significantly between the two TI-RADS categories, reflecting consistent image interpretation and patient management regardless of the system.