3D ultrasonography is as accurate as low-dose CT in thyroid volumetry

Summary

Aim: The purpose of this study was to compare thyroid volumetry by three-dimensional mechanically swept ultrasonography (3DmsUS) and low-dose computed tomography (ldCT). Patients, methods: 30 subjects referred for radioiodine therapy of benign thyroid diseases were subjected to 3DmsUS and ldCT. A prerequisite of 3DmsUS analyses was that the scans had to capture the entire thyroid, excluding therefore cases with a very large volume or retrosternal portions. The 3DmsUS data were transformed into a DICOM format, and volumetry calculations were performed via a multimodal workstation equipped with standard software for cross-sectional imaging. Volume was calculated applying both the ellipsoid model and a manually tracing method. Statistical analyses included 95% confidence intervals (CI) of the means and limits of agreement according to Bland and Altman, the latter including 95% of all expected values. Results: Volumetric measurements by 3DmsUS and ldCT resulted in very high, significant correlation coefficients, r = 0.997 using the ellipsoid model and r = 0.993 with the manually tracing method. The mean relative differences of the two imaging modalities proved very small (−1.2±4.0% [95% CI −2.62; 0.28] using the ellipsoid model; −1.1±5.2% [95% CI −2.93; 0.80] using the manually tracing method) and the limits of agreement sufficiently narrow (−9.1% to 6.8%; −11.3% to 9.2%, respectively). Conclusion: For moderately enlarged thyroids, volumetry with 3DmsUS proved comparable to that of ldCT, irrespective of whether the ellipsoid model or the manually tracing method was applied. Thus, 3DmsUS qualifies as a potential alternative to ldCT, provided that the organ is completely accessible. The use of a standard workstation for cross-sectional imaging with routine software did not prove problematic.

Zusammenfassung

Ziel dieser Studie ist der Vergleich der Schilddrüsenvolumetrie mittels dreidimensionalem mechanisch geschwenktem Ultraschall (3DmsUS) und Niedrigdosis-Computertomographie (ldCT). Patienten, Methoden: Bei 30 Patienten, die aufgrund einer gutartigen Schilddrüsenerkrankung eine Radioiodthera- pie erhielten, wurde zusätzlich 3DmsUS und ldCT durchgeführt. Voraussetzung für den 3DmsUS war, dass die komplette Schilddrüse erfasst werden konnte. Die 3DmsUS-Daten wurden in ein DICOM-Format umgewandelt und anschließend die Volumenberechnungen mit einer Standardsoftware für Schnittbildge- bung ausgeführt. Das Volumen wurde mit der Ellipsoidformel und einer manuellen Kontu rierungsmethode ermittelt. Die Statistik wurde mit 95%-Konfidenzintervallen der Mittelwerte und den „limits of agreement” nach Bland und Altmann durchgeführt. Ergebnisse: Der Vergleich der beiden Volumetriemethoden (3DmsUS und ldCT) ergab eine positive, signifikante Korrelation für die Ellipsoidformel (r = 0.997) und die manuelle Konturie- rungsmethode (r = 0.993). Die durchschnittlichen relativen Differenzen zwischen den Volumetriemethoden waren niedrig (Ellip soidformel: −1.2±4.0% [95% CI −2.62; 0.28]; manuelle Konturierungsmethode: −1.1± 5.2% [95% CI −2.93; 0.80]). Die „limits of agreement” waren ausreichend eng (Ellip- soidformel: −9.1% bis 6.8%; manuelle Kon turierungsmethode: −11.3% bis 9.2%). Schlussfolgerung: 3DmsUS und ldCT liefern bei moderat vergrößerten Schilddrüsen vergleichbare Volumina, unabhängig davon, ob die Ellipsoidformel oder die manuelle Konturierungsmethode angewandt wird. Daher stellt der 3DmsUS eine potenzielle Alternative zur ldCT dar, vorausgesetzt, dass das Organ vollständig abgebildet werden kann. Der Einsatz einer Standardsoftware für Schnittbildgebung zur Volumenberechnung war unproblematisch.

Keywords

Thyroid gland volume - thyroid gland ultra sonography - thyroid gland computed tomo graphy - thyroid gland three-dimensional imaging - volumetry methods

Schlüsselwörter

Schilddrüsenvolumen - Schilddrüsen-Ultraschall - Schild drüsen-CT - dreidimensionale Bildgebung - Volumetrie

• References

• 1 Andermann P, Schlogl S, Mader U. et al. Intra-and interobserver variability of thyroid volume measurements in healthy adults by 2D versus 3D ultrasound. Nuklearmedizin 2007; 46: 1-7.
• 2 Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1: 307-310.
• 3 Brunn J, Block U, Ruf G. et al. Volumetric analysis of thyroid lobes by real-time ultrasound. Dtsch Med Wochenschr 1981; 106: 1338-1340.
• 4 Darr AM, Opfermann T, Niksch T. et al. Lowactivity ¹²⁴I-PET/low-dose CT versus ^99mTc-pertechnetate planar scintigraphy or ^99mTc-pertechnetate single-photon emission computed tomography of the thyroid: A pilot comparison. Clin Nucl Med 2013; 38: 770-777.
• 5 Freesmeyer M, Darr A, Schierz JH. et al. 3D ultrasound DICOM data of the thyroid gland. First experiences in exporting, archiving, second reading and 3D processing. Nuklearmedizin 2012; 51: 73-78.
• 6 Hermans R, Bouillon R, Laga K. et al. Estimation of thyroid gland volume by spiral computed tomography. Eur Radiol 1997; 7: 214-216.
• 7 Knudsen N, Bols B, Bulow I. et al. Validation of ultrasonography of the thyroid gland for epidemiological purposes. Thyroid 1999; 9: 1069-1074.
• 8 Kot BC, Sin DM, Ying M. Evaluation of the accuracy and reliability of two 3-dimensional sonography methods in volume measurement of small structures: an in vitro phantom study. J Clin Ultrasound 2009; 37: 82-88.
• 9 Lyshchik A, Drozd V, Reiners C. Accuracy of three-dimensional ultrasound for thyroid volume measurement in children and adolescents. Thyroid 2004; 14: 113-120.
• 10 Malago R, D’Onofrio M, Ferdeghini M. et al. Thyroid volumetric quantification: comparative evaluation between conventional and volumetric ultrasonography. J Ultrasound Med 2008; 27: 1727-1733.
• 11 Ng E, Chen T, Lam R. et al. Three-dimensional ultrasound measurement of thyroid volume in asymptomatic male Chinese. Ultrasound Med Biol 2004; 30: 1427-1433.
• 12 Nygaard B, Nygaard T, Court-Payen M. et al. Thyroid volume measured by ultrasonography and CT. Acta Radiol 2002; 43: 269-274.
• 13 Ozgen A, Erol C, Kaya A. et al. Interobserver and intraobserver variations in sonographic measurement of thyroid volume in children. Eur J Endocrinol 1999; 140: 328-331.
• 14 Pang BS, Kot BC, Ying M. Three-dimensional ultrasound volumetric measurements: is the largest number of image planes necessary for outlining the region-of-interest?. Ultrasound Med Biol 2006; 32: 1193-1202.
• 15 Rago T, Bencivelli W, Scutari M. et al. The newly developed three-dimensional (3D) and two-dimensional (2D) thyroid ultrasound are strongly correlated, but 2D overestimates thyroid volume in the presence of nodules. J Endocrinol Invest 2006; 29: 423-426
• 16 Reinartz P, Sabri O, Zimny M. et al. Thyroid volume measurement in patients prior to radioiodine therapy: comparison between three-dimensional magnetic resonance imaging and ultrasonography. Thyroid 2002; 12: 713-717.
• 17 Riccabona M, Nelson TR, Pretorius DH. Three-dimensional ultrasound: accuracy of distance and volume measurements. Ultrasound Obst Gyn 1996; 7: 429-434.
• 18 Schlogl S, Andermann P, Luster M. et al. A novel thyroid phantom for ultrasound volumetry: determination of intraobserver and interobserver variability. Thyroid 2006; 16: 41-46.
• 19 Schlogl S, Werner E, Lassmann M. et al. The use of three-dimensional ultrasound for thyroid volumetry. Thyroid 2001; 11: 569-574.
• 20 Shin JJ, Grillo HC, Mathisen D. et al. The surgical management of goiter: Part I. Preoperative evaluation. Laryngoscope 2011; 121: 60-67.
• 21 Shu J, Zhao J, Guo D. et al. Accuracy and reliability of thyroid volumetry using spiral CT and thyroid volume in a healthy, non-iodine-deficient Chinese adult population. Eur J Radiol 2011; 77: 274-280.
• 22 Tong S, Cardinal HN, McLoughlin RF. et al. Intra-and inter-observer variability and reliability of prostate volume measurement via two-dimensional and three-dimensional ultrasound imaging. Ultrasound Med Biol 1998; 24: 673-681.
• 23 Van Isselt JW, de Klerk JM, van Rijk PP. et al. Comparison of methods for thyroid volume estimation in patients with Graves’ disease. Eur J Nucl Med Mol Imaging 2003; 30: 525-531.
• 24 Volzke H, Ludemann J, Robinson DM. et al. The prevalence of undiagnosed thyroid disorders in a previously iodine-deficient area. Thyroid 2003; 13: 803-810.
• 25 Ying M, Pang BS. Three-dimensional ultrasound measurement of cervical lymph node volume. Br J Radiol 2009; 82: 617-625.
• 26 Ying M, Yung DM, Ho KK. Two-dimensional ultrasound measurement of thyroid gland volume: a new equation with higher correlation with 3-D ultrasound measurement. Ultrasound Med Biol 2008; 34: 56-63.