Variation in thyroid volumes due to differences in the measured length or area of the cross‐sectional plane: A validation study of the ellipsoid approximation method using CT images

Purpose This study examined the variation in thyroid volume determined by ellipsoid approximation method due to differences measured length or area of cross-sectional plane CT images. Methods Forty-five patients with Graves' disease were included this retrospective study. We designated three-dimensional volumes extracted manually (VCT) as reference data and calculated five approximate for comparison: (a) mean 8100 different depending on diameter at midpoint major axis, (Vellipsoid,mean); (b) using maximum its orthogonal diameter, (Vellipsoid,maxlength); (c) (Vellipsoid,maxvolume); (d) minimum (Vellipsoid,minvolume) volumes; (e) an equivalent circle (Vellipsoid,Heywood). Results Thyroid obtained via varied a error approximately 20%, while concordance correlation coefficient (CCC) differed each volume. Among these volumes, Vellipsoid,mean Vellipsoid,Heywood good agreement VCT, according single regression analyses resultant CCC values, errors 0.1% 10.4%, respectively. Conclusion While approximated vastly reduced errors, we recommend utilizing volumetry if measurement accuracy is required.