Table 1.

Summary of the main features of ultrasound-based thyroid nodule systems.

ACR-TIRADS	Korean System	UK BTA System
TR 1 0 points Benign	K-TIRADS 1: no nodule	U1: No nodule
TR 2 2 points no suspicious	K-TIRADS 2: Benign	U2: Benign hyperechoic or isoechoic with a halo cystic change with ring-down artifact (colloid) microcystic or spongiform appearance peripheral egg-shell calcification peripheral vascularity
TR 3 3 points Mildly suspicious	K-TIRADS 3: Low partially cystic/isohyperechoic with no suspicious features	U3: Indeterminate solid homogenous markedly hyperechoic nodule with halo (follicular lesions) hypoechoic with equivocal echogenic foci or cystic change mixed or central vascularity
TR 4 TR4a = 4 TR4b = 5 TR4c = 6 from 4 to 6 points Moderately suspicious	K-TIRADS 4: Intermediate as for K-TIRADS 3 but with any suspicious features or as for K-TIRADS 5 without suspicious features	U4: Suspicious solid hypoechoic (compared with thyroid) solid very hypoechoic (compared with strap muscles) hypoechoic with disrupted peripheral calcification lobulated outline
TR 5 > 7 points Highly suspicious	K-TIRADS 5: High solid hypoechoic nodule with any suspicious feature	U5 Malignant solid hypoechoic with a lobulated or irregular outline and microcalcification papillary carcinoma solid hypoechoic with a lobulated or irregular outline and globular calcification medullary carcinoma intranodular vascularity taller than wide axially (AP > ML) characteristic associated lymphadenopathy

American College of Radiology Thyroid Imaging, Reporting and Data System (ACR-TIRADS); K-TIRADS: Korean Tirads; UK BTA TIRADS: United Kingdom British Thyroid Association TIRADS. TR = TI-RADS; AP = anteroposterio; ML = mediolateral.