Enhancing the Detection of Malignancy in Thyroid Nodules by Assessing Longitudinal Diameter-to-Anteroposterior Diameter Ratio

The aim of investigate the ability of 3-dimensional diameter measurements of the nodule to predict malignant nodules. Adult patients with thyroid nodules who underwent thyroid surgery or fine-needle aspiration biopsy between December 2017 and December 2022 were included in this retrospective study. Thyroid ultrasound images and final pathology results were collected. Nodule size was remeasured using recorded ultrasound images in 3 dimensions (longitudinal, anteroposterior, and transverse). The ratios of the longitudinal diameter to the transverse diameter (L/T), the longitudinal diameter to the anteroposterior diameter (L/AP), and the anteroposterior diameter to the transverse diameter (AP/T) were calculated. The recent American College of Radiology TI-RADS system was used for the ultrasonographic scoring of the nodules. Patients were grouped as benign or malignant based on their final pathology results. In total, 398 (70.69%) patients had benign nodules and 165 (29.31%) patients had malignant nodules. The malignant group was significantly older than the benign nodule group (P = 0.011), while sex distributions were similar (P = 0.101). Malignant nodules could be predicted with the following cutoff values: L/T ≤ 0.97 (P < 0.001), L/AP ≤1.6 (P < 0.001), and AP/T > 1.0 (P < 0.001) or >0.94 (P < 0.001). Multivariable logistic regression indicated that low (≤1.6) L/AP ratio and high scores for echogenicity, shape, margin, and echogenic foci were independently associated with malignancy. Combining the L/AP ratio with the AP/T ratio could improve the discrimination of malignant thyroid nodules from benign nodules. Incorporating the L/AP ratio into new risk classification systems warrants careful consideration.