Differentiating benign from malignant thyroid nodules: comparison of 2- and 3- dimensional sonography

To compare the diagnostic performance of radiologists and to determine interobserver and intraobserver variability with regard to differentiation of benign and malignant thyroid nodules using prospectively obtained 2-dimensional (2D) and 3-dimensional (3D) sonograms.

This study had Institutional Review Board approval, and the requirement for patient informed consent was waived. Conventional 2D and 3D sonograms were obtained from 82 patients (age range, 20-77 years; mean age, 51 years) with 91 thyroid nodules (15 cancers, 13 indeterminate, and 63 benign lesions) before diagnostic fine-needle aspiration. Three radiologists reviewed stored 2D and 3D images for internal content, shape, margin, echogenicity, echo texture, and the presence of calcification and estimated the level of suspicion as to the probability of malignancy according to known sonographic criteria. The diagnostic performance of 2D images was compared with that of 3D images.

For all readers, interpretation using 3D images was more sensitive and specific than that using 2D images for diagnosis of malignant thyroid nodules, with the exception of specificity for reader 1. However, differences were not statistically significant (P > .05). Area under the receiver operating characteristic curve values were 0.83 for 2D images and 0.92 for 3D images for reader 1; 0.78 for 2D images and 0.89 for 3D images for reader 2; and 0.89 for 2D images and 0.93 for 3D images for reader 3. Interobserver agreement between the 3 radiologists for differentiation of benign and malignant thyroid nodules was better for 3D images (κ = 0.49) than for 2D images (κ = 0.15). Intraobserver variability for nodule descriptions and assessments using 3D and 2D images was fair to moderate.

The performance of radiologists and interobserver and intraobserver agreement for characterization of thyroid nodules were better when 3D sonograms were used than when 2D sonograms were used.