The Ultrasound Elastography for the Indeterminate Thyroid Nodules in Conventional Ultrasound

Abstract

PURPOSE To determine the usefulness of real-time freehand US elastography to differentiate malignant from indeterminate thyroid nodules in conventional US (CUS), with pathologic diagnosis as the reference standard

METHOD AND MATERIALS Between Oct. 2007 and Jan. 2008, conventional ultrasonography (CUS) in 78 thyroid nodules (61 benign; 17 malignant) of 56 patients (F: M=71: 7, mean age of 50.2 years) who were scheduled to undergo thyroidectomy showed indeterminate findings; no malignant sign (taller shape, speculated margin, calcification except rim-type, markedly hypoechoic), and not-definite benign (cyst or predominantly cystic nodule). The elasticity image was obtained with light compression and the elasticity score (1-5) according to the degree and distribution of strain. The proportion of no strain (PNS) per each nodule was assessed. Mean E scores and proportion of NS in benign and malignant nodules were examined by using a Student t-test. We evaluated the diagnostic performance to differentiate malignancy from benign lesions by using a receiver operating characteristic analysis to compare the area under the curve, sensitivity, specificity and accuracy at the cut-off value.

RESULTS For E score, the mean + standard deviation was 2.9 + 0.8 for malignant lesions and 2.0 + 0.5 for benign lesions (P<.001). For PNS, the mean + standard deviation was 63.2 + 27.8 for malignant lesions and 21.0 + 20.4 for benign lesions (P<.001). The area under the curve of E score and PNS was 0.814 and 0.884. There was no significant difference of AUC between E score and PNS (p=0.143). Sensitivity, specificity, and accuracy of E score at the cut-off value between 2 and 3 were 70.6%, 85.2%, and 76.0%, respectively. Those of PNS at the cut off value of 20% were 88.2%, 77.0%, and 78.2%, respectively.

CONCLUSION For the differential diagnosis of indeterminate thyroid nodules in CUS, US elastography would be valuable.

CLINICAL RELEVANCE/APPLICATION For the thyroid nodules with indeterminate findings of CUS for, US elastography may be useful as an adjunctive method to further categorize the nodules.