Value Of Anteroposterior-To-Transverse Ratio in Ultrasonic Diagnosis of Thyroid Nodule in Different Locations.

Purpose: To investigate the value of anteroposterior-to-transverse ratio (ATR) and the effect on features of nodules in ultrasound (US) diagnosis of thyroid nodules in different locations.  Methods: The nodules were divided into three groups according to the different nodule location: isthmus group; upper and lower poles of bilobed thyroid group; and the middle of the bilobed thyroid group. The diameters of the nodules were recorded, and ATR of the nodule was calculated on the transverse and longitudinal sections. The transverse and the longitudinal sections of ATR of thyroid nodules in different groups were compared.  Result: The transverse section of ATR was significantly different among the three groups (p = 0.001). In addition, there are significant differences in many US features among three groups, including nodule composition, thyroid parenchyma, morphology, echogenicity, shape, calcifications, vascularity, nodule ACR TI-RADS and histopathologic (all p < 0.05). In the group of upper and lower poles of bilobed thyroid, significant difference was found between the transverse and the longitudinal section of ATR (p = 0.019). The cut-off values of transverse section and longitudinal section of ATR were 0.967 and 0.750, respectively.  Conclusion: The transverse section of ATR at different location of thyroid may be a predictor for malignancy with clinical diagnostic significance.