Application Of Three-dimensional Volume Sonography In Differential Diagnosis Of Benign And Malignant Solid Thyroid Nodules

Objective: For the superiorities of high resolution, real-time imaging, repeatability, poor radioaction and affordability, conventional ultrasonography has been the best known diagnostic tool for evaluation of thyroid disease. High-frequency and color doppler ultrasound improve the level of discovery and diagnose of thyroid nodules, resulting in the early detection of thyroid cancer, especially of microcarcinoma. Nevertheless, some problematic issues remain for the complex and overlapping sonography features. Due to recent developments in computer techniques and scanner technology, three-dimensional sonography has improved rapidly and been applied in clinic extensively. Three-dimensional sonograms can be reconstructed from data obtained from a single sweep of an ultrasound beam across the involved organ, obtaining more information especially the coronal plane sonography against two-dimensional sonograms. As a consequence, relative positions in each tomographic section are indicative of the exact anatomic structures. This study aims to evaluate the clinical value and coronal plane sonography features of three-dimensional volume sonography in differential diagnosis of solid thyroid nodules.Methods: From December 2014 to January 2015, conventional 2D and 3D sonograms were obtained from 176 patients including forty-two male and one hundred and thirty-four female( age range 21-76 years, mean age 48.4±11.5 years) with 214 solid thyroid nodules(size range 0.5-3.8cm). All cases were confirmed by surgery and pathology. All sonograms were obtained using by a linear array 5- to 12- MHz transducer and a volume transducer 5- to 13- MHz of Philips IU22. For 2D images, multiple sections were scanned to observe sonographic features of thyroid nodules for the location, size, shape, margin, halo, calcification, and 2D sonograms diagnosis were recorded. For 3D images, a volume box size was selected adjusted to the size of the nodule, then the volume scan was performed automatically to collect and save the volume date. Blind method were adopted in retrospective analyze of 3D volume date and three-dimensional reconstruction was performed for the region of interest. Entire morphology were observed in multi-view with Volume rendering. The numerous, continuous slices, from one border to opposite border of the nodule were evaluated interactively with MPR and islice, and 3D sonography diagnosis were recorded. The coronal plane sonography features of benign and malignant nodules were analyzed comparatively with respect to the histological results. For evaluation of risk factor of thyroid cancer identified by coronal plane, multiple logistic regression analysis was applied. The pathology diagnosis was considered as the gold standard to calculate the sensitivity, specificity, PPV(positive predictive value), NPV(negative predictive value), accuracy of 2D and 3D sonograms. The diagnostic performance was compared.Results: Of the 176 patients with 214 solid thyroid nodules, 101 were benign, 113 were malignant. The coronal plane sonography showed significant difference between benign and malignant solid thyroid nodules in the characteristics of shape, margin, echogenicity, and the presence of micro-calcification and angulation or spiculation(P<0.05), except of macro-calcification(P>0.05). Benign solid thyroid nodules showed various interior echoes, and accounted for a high proportion when nodules showed ovoid to round shape, well defined margin, without angulation or spiculation, and without micro-calcification, whereas thyroid cancer showed hypo-echogenicity, irregular shape, poorly defined margin, angulation or spiculation, part with calcification.Multiple logistic regression analysis was built with scores of coronal plane sonography as independent variables, and pathology types as dependent variables. Our study revealed four features for thyroid cancer: irregular shape, poorly defined margin, angulation or spiculation, hypo- echogenicity(P<0.05), except of micro-calcification(P>0.05).For totally 214 solid thyroid nodules, 177 cases were correctly diagnosed and 37 were wrongly diagnosed by two-dimensional sonograms. The sensitivity, specificity, accuracy of 2D ultrasonography in diagnosis of malignant solid thyroid nodules was 87.6%, 77.2%, 82.7%. In contrast, 186 cases were correctly diagnosed and 28 were wrongly diagnosed by three-dimensional sonograms. The sensitivity, specificity, accuracy of 3D ultrasonography in diagnosis of malignant solid thyroid nodules was 91.2%, 82.2%, 86.9%, which were superior to 2D sonograms. However, the two sonographic techniques were not found to differ significantly in terms of diagnostic performance evaluated by chi-square test of paired(P>0.05).Conclusion: There is a significant difference between benign and malignant solid thyroid nodules in coronal plane features of shape, margin, echogenicity, and the presence of micro-calcification and angulation or spiculation. Irregular shape, poorly defined margin, angulation or spiculation, hypo-echogenicity account as independent sonographic risk factors for malignant solid thyroid nodules. 3D volume sonography appears to be an effective method for thyroid nodule evaluation, while further studies are warranted.