Purpose: Thyroid ultrasound (US) with two dimensional (2-D) probe and 3-D volumetric probe was performed in healthy adults to determine appropriate coefficient in evaluating thyroid gland volume using ellipsoid formula.
Subjects and Methods: 29 adults with normal thyroid function and negative anti-thyroid antibodies underwent thyroid ultrasound using 2-D probe and 3-D volumetric probe. In 2-D US, Thyroid volume (V) was calculated using ellipsoid formula (V=A×width×length×depth, where A=coefficient) with varied coefficients (0.47, 0.52 and 0.7). In 3-D US, volume was calculated by multi-planar volume approximation and data processing software. Results from 2-D US were compared with those from 3-D US, which was considered as the standard in our study.
Results and Discussion: Significant correlation was observed between thyroid volume determined by 2-D US with varied coefficients vs that by 3-D US. The average volume of thyroid gland (cm3) by 2-D US with coefficient of 0.47, 0.52, and 0.7 and that by 3-D volumetric probe were 9.4±3.7, 10.2±4.0, and 13.7±5.4 and 13.4±5.0, respectively. Results from 2-D US using coefficient of 0.47 and 0.52 were smaller than those from 3-D US (p<0.05). With the use of 0.7 as a coefficient, thyroid volume from 2-D US was comparable to that from 3-D US.
Conclusion: Our study suggests that coefficient of 0.7 gives appropriate results in evaluating thyroid volume by 2-D US and ellipsoid formula unless thyroid evaluate has substantial deformity or lumpy contour.
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