Detection of Thyroid Pyramidal Lobe by Ultrasound Versus Computed Tomography

Abstract

The prevalence and features of the thyroid pyramidal lobe (TPL) on computed tomography (CT) have been reported, but no ultrasound (US) study has been found. The purposes of the current study were to assess the sonographic prevalence and features of TPLs and to compare the US and CT parameters of TPLs. From November 2012 to February 2013, a total of 160 patients who were scheduled for surgical treatment of thyroid cancers and follicular neoplasms were enrolled. A single radiologist prospectively evaluated the presence and features of TPLs on preoperative thyroid US, noting the size, location, degree of continuity with the main thyroid gland, and superior extent of each TPL. On a different day, the same radiologist retrospectively evaluated CT findings in the same patients from a picture archiving and communication system. Ultrasound revealed TPLs in 82 cases (50.6%) and CT revealed TPLs in 96 cases (59.3%). Thyroid pyramidal lobes predominantly originated from the left thyroid lobe on both US (34/82, 41.5%) and CT (40/96, 41.7%). The mean length, anteroposterior diameter, transverse diameter, and volume of the TPLs were 20.9 mm, 2.0 mm, 5.8 mm, and 268.6 mm on US and 22.8 mm, 1.9 mm, 6.1 mm, and 344.0 mm on CT, respectively. When CT findings were used as the reference standard, the sensitivity, specificity, positive and negative predictive values, as well as accuracy of US for detecting TPLs were 82.3, 95.3, 93.3, 78.2, and 87.5%, respectively. Like neck CT, thyroid US may be useful in evaluating TPLs.