Korean J Radiol.  2015 Apr;16(2):402-409. 10.3348/kjr.2015.16.2.402.

Comparison between Ultrasonography and Computed Tomography for Detecting the Pyramidal Lobe of the Thyroid Gland: A Prospective Multicenter Study

• Kim DW
• Jung SL
• Kim J
• Ryu JH
• Sung JY
• Lim HK

• KMID: 2070184
• DOI: http://doi.org/10.3348/kjr.2015.16.2.402

Abstract

OBJECTIVE
To compare the detection rates of the pyramidal lobe of the thyroid gland (TPL) using ultrasonography (US) and computed tomography (CT) in a prospective multi-center study.
MATERIALS AND METHODS
We enrolled 582 patients who underwent neck CT at six institutions. Each radiologist prospectively evaluated the presence and features of TPLs on thyroid US. Radiologists were divided into two groups according to their previous experience in detecting TPL on US or CT. The same radiologist also retrospectively assessed CT findings, blinded to the corresponding US findings.
RESULTS
The pyramidal lobe of the thyroid glands were detected in 230 cases (39.5%) on US and in 276 cases (47.6%) on CT. The TPL detection rate at the six institutions ranged from 22.0% to 59% for US and from 34.1% to 59% using CT. There were significant differences between US and CT in the detection rate, length, anteroposterior diameter, volume, and superior extent of TPL (p < or = 0.027). The TPL detection rates on both US and CT (p < 0.001) differed significantly according to the experience level of the radiologists. When the CT result was used as a reference standard, the sensitivity, specificity, positive and negative predictive values, as well as the accuracy of US for TPL detection were 72.6%, 91.5%, 89.3%, 77.3%, and 82.1%, respectively.
CONCLUSION
Our prospective multicenter study revealed that US could detect TPL with relatively high diagnostic accuracy compared to CT. Because the detection rate of TPL varied significantly according to the radiologists' level of experience, careful inspection is necessary to avoid imaging pitfalls and ensure appropriate evaluation of TPL on both US and CT.

Keyword

Thyroid; Variation; Pyramidal lobe; Ultrasonography; Computed tomography; Anatomy

MeSH Terms

Adult
Aged
Diagnostic Imaging
Female
Humans
Male
Middle Aged
Neck/*radiography/*ultrasonography
Prospective Studies
Retrospective Studies
Sensitivity and Specificity
Thyroid Gland/pathology/*radiography/*ultrasonography
Tomography, X-Ray Computed/*methods
Young Adult

Figure

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  Fig. 1 Left pyramidal lobe detected on US and CT in 58-year-old woman. Transverse (A) and longitudinal (B) gray-scale sonograms show left pyramidal lobe (arrows). Non-enhanced (C) and contrast-enhanced (D) axial CT images of left pyramidal lobe (arrows) show same attenuation and enhancement as main thyroid gland (arrowheads).

• 

  Fig. 2 Fatty tissue mimicking thyroid pyramidal lobe on ultrasonography in 49-year-old woman. Transverse (A) and longitudinal (B) gray-scale sonograms show longitudinally arranged structure mimicking thyroid pyramidal lobe (arrows). Nonenhanced (C) and contrast-enhanced (D) axial CT images shows only fatty tissue in same position (arrows), and they show different attenuation and enhancement from main thyroid gland (arrowheads).

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