Dual-plane taller-than-wide definition for thyroid nodules: comparative analysis across TIRADS

The selection of ultrasound (US) plane for evaluating the taller-than-wide (TTW) shape remains controversial. This study aimed to determine whether the diagnostic value of TTW criteria differs when used alone or in combination with other US features, and to identify the optimal TTW criterion across four major Thyroid Imaging Reporting and Data Systems (TIRADS: Chinese (C)-TIRADS, American College of Radiology (ACR)-TIRADS, European (EU)-TIRADS and Korean (K)-TIRADS).

Preoperative US images of thyroid nodules were reviewed retrospectively. Four TTW criteria were defined as follows: transverse plane only (T-only), longitudinal plane only (L-only), both planes (Dual-plane), and either one or both planes (Single- or dual-plane). Diagnostic performance was assessed using the area under the receiver operating characteristic curve (AUC) and net reclassification improvement (NRI) for malignancy prediction and fine-needle aspiration (FNA) guidance.

Among 1125 nodules, 558 (49.6%) were benign and 567 (50.4%) were malignant. Using the TTW shape alone, Single- or dual-plane achieved the highest AUC for malignancy (0.813). Within TIRADS, Dual-plane demonstrated the highest AUCs in C-TIRADS (0.884) and EU-TIRADS (0.874) and improved reclassification, whereas in ACR-TIRADS and K-TIRADS, Dual-plane and Single- or dual-plane performed similarly and outperformed the T-only and L-only. For FNA guidance, the Dual-plane also showed improvements in C-TIRADS and ACR-TIRADS.

The optimal TTW US plane differs when applied alone versus when combined with other suspicious US features. Within the TIRADS, assessment of the TTW shape in both transverse and longitudinal planes achieves superior accuracy and contributes to improving malignancy diagnosis and FNA decision-making.

Question Which TTW criterion provides the best diagnostic performance for malignancy risk stratification and FNA guidance across the four major TIRADS? Findings Dual-plane TTW yielded the best performance in C-TIRADS and EU-TIRADS, and improved FNA guidance in C-TIRADS and ACR-TIRADS versus other TTW criteria. Clinical relevance The stricter criterion not only improves the malignancy diagnosis but also provides better guidance for biopsy, offering valuable evidence for refining future guideline recommendations and standardizing the evaluation of thyroid nodules.