Objective: The aim of this study was to compare the accuracy of thyroid nodule volume measurements performed by 2- and 3-dimensional ultrasonography and to evaluate the dependence of volume measurement results on nodule size and echographic characteristics.
Methods: Results of multiple 2- and 3-dimensional ultrasonographic volume measurements of thyroid nodules in 102 children with different variants of thyroid nodular disease were reviewed retrospectively. The standardized difference, within-observer variability, and repeatability were estimated for both 2- and 3-dimensional ultrasonography. The mean age of the patients +/- SD in the examined group was 14.9 +/- 2.8 years; the mean volume of thyroid nodules was 0.78 +/- 0.13 mL.
Results: The SD of the normalized difference for 3-dimensional ultrasonography (2.8%) showed the clear superiority of its accuracy over 2-dimensional ultrasonography (15.9%; F test, P < .01). Intraobserver variability and repeatability for both examined methods had significant dependence on the nodule outline. For 2-dimensional ultrasonography, the intraobserver variability increased from 14.0% in nodules with a regular outline to 24.5% in those with an irregular outline (P < .001), and for 3-dimensional ultrasonography, it increased from 5.1% to 9.3% (P < .001). Intraobserver repeatability dropped from 85.4% in regular nodules to 74.6% in irregular nodules (P < .001) for 2-dimensional ultrasonography and from 94.7% to 90.4% (P < .001) for 3-dimensional ultrasonography.
Conclusions: Volume measurements by 3-dimensional ultrasonography are more accurate, showing lower intraobserver variability and higher repeatability, than those made by 2-dimensional ultrasonography with less dependence on nodule size and echographic characteristics.