Comparison of methods for thyroid volume estimation in patients with Graves' disease

Abstract

Individualised dosage models are frequently applied for radioiodine therapy in patients with Graves' hyperthyroidism, especially in Europe. In these dosage schemes the thyroid volume is an important parameter. Thyroid volume determinations are usually made with ultrasonography or with thyroid scintigraphy, although the accuracy of planar scintigraphy for this purpose is not well established. The aim of this study was to compare the accuracy of three modalities for the determination of the thyroid volume in patients with Graves' disease: planar scintigraphy (PS), single-photon emission tomography (SPET) and ultrasonography (US). These three modalities were compared with magnetic resonance imaging (MRI) as the gold standard. Thyroid volume estimations were performed in 25 patients with Graves' disease. The PS images were subjected to filtering and thresholding, and a standard surface formula was used to calculate the thyroid volume. With SPET the iteratively reconstructed thyroid images were filtered, and after applying a threshold method an automatic segmentation algorithm was used for the volume determinations. Thyroid volumes were estimated from the US images using the ellipsoid volume model for multiple two-dimensional measurements. For MRI, thyroid segmentation was performed manually in gadolinium-enhanced T1-weighted images and a summation-of-areas technique was used for the volume measurements. The thyroid volumes calculated with MRI were 25.0+/-13.8 ml (mean+/-SD, range 7.0-56.3 ml). PS correlated poorly with MRI ( R(2)=0.61) and suffered from a considerable bias (-4.0+/-17.6 ml). The differences between PS and MRI volume estimations had a very large spread (33+/-58%). For SPET both the correlation with MRI ( R(2)=0.84) and the bias (1.8+/-11.9 ml) were better than for PS. US had by far the best correlation with MRI ( R(2)=0.97) and the best precision, but the bias (6.8+/-7.5 ml) was not negligible. In conclusion, SPET is preferred over PS for accurate measurements of thyroid volume. US is the most accurate of the three modalities, if a correction is made for bias.

The estimation of the thyroid volume before surgery—an important prerequisite for minimally invasive thyroidectomy

“…In this context, however, it is worth considering that a very similar formula was reported by van Isselt et al [7] who correlated US-TV with MRI measured TV on a series of 25 patients with Graves' disease.…”

“…Moreover, it has been shown that in nodular glands, US overestimates TV compared to 3D-US [10]. In a paper in which MRI was assumed as the gold standard method for in vivo TV measurement, it has been demonstrated that two-dimensional US was, among other imaging techniques, the most accurate method [7]. Furthermore, in a more recent and prospective report in which US-TV was compared with that measured post-surgery, it was shown that in 90% of cases, thyroid volume was underestimated by ultrasonography.…”

“…In this context, several attempts have been made to estimate the accuracy of twodimensional US thyroid volume with respect to other imaging techniques, including planar scintigraphy, 3D-US, computed tomography (CT), single-photon emission tomography, and magnetic resonance imaging (MRI) [6][7][8][9][10][11][12][13]. In particular, the report from van Isselt et al [7] in which MRI was assumed as the gold standard method for TV measurement demonstrated that US, among other imaging techniques, was the most accurate. However, accuracy of US-TV was also evaluated by comparison with postsurgery or autopsy specimens demonstrating that thyroid volume is underestimated by ultrasound [14][15][16].…”

“…However, its concordance with respect to real TV is not yet well defined [6,7]. In this context, several attempts have been made to estimate the accuracy of twodimensional US thyroid volume with respect to other imaging techniques, including planar scintigraphy, 3D-US, computed tomography (CT), single-photon emission tomography, and magnetic resonance imaging (MRI) [6][7][8][9][10][11][12][13].…”

Local bupivacaine for postoperative pain management in thyroidectomized patients: A prospective and controlled clinical study

“…Ellipsoid formula with correction factor, which is the most commonly used two-dimensional ultrasonographic mathematical method to estimate thyroid gland volume was used for calculation (24)(25)(26). This formula refers to width ´ depth ´ length ´ 0.524 for each lobe.…”