갑상선 결절의 감별을 위한 탄성초음파 : 고식적 초음파와의 비교

Abstract

Purpose To compare the diagnostic performance of real-time freehand ultrasound (US) elastography with conventional ultrasonography (CUS) in differentiating malignant from benign thyroid nodules and to assess the usefulness of US elastography in evaluating the thyroid nodules with indeterminate findings in CUS.

Materials and Methods Between October 2007 and February 2008, we performed both CUS and US elastography for the patients who were scheduled to undergo thyroid operation. The results of CUS were divided into three categories; benign, indeterminate, and malignancy. The elasticity (E) score was assigned from 1 to 5 according to the degree and distribution of strain induced by light compression. Mean E scores in malignant and benign nodules were examined by using a Student t-test. We evaluated the diagnostic performance of CUS and US elastography in differentiating malignant from benign lesions by using a ROC analysis to compare the area under the curve (AUC), sensitivity and specificity at the optimal cut-off value.

Results Real-time US elastography and CUS were performed in 203 thyroid nodules (113 malignant; 90 benign) of 114 patients (F: M=101:13). The mean age of the patients was 49 years. The mean E score in total nodules was significantly higher in the malignant nodules (3.8 ± 1.0) than benign nodules (2.0 ± 0.6) (p< 0.001). There was no malignancy in nodules with E score 1, and no benign histology in nodules with E score 4 or 5. In CUS malignant category, the mean E score was significantly higher in malignant nodules (3.9 ± 0.9) than benign nodules (2.6 ± 0.5) (p< 0.001). In CUS indeterminate category, the mean E score was also significantly higher in the malignant nodules (3.1 ± 0.8) than benign nodules (2.0 ± 0.5) (p< 0.001). The AUC for elastography (0.933) was slightly higher than that for CUS (0.894), however, those values had no significant difference (p=0.102). The overall sensitivity and specificity of CUS at the cutoff point between CUS indeterminate and malignant category were 87.6% and 88.9%, respectively. Those of E score at the cutoff point between 2 and 3 were 92.0% and 81.1%, respectively.

Conclusion For the differential diagnosis of thyroid nodules, the diagnostic performance of elasticity score was at least equivalent to that of CUS. Although thyroid nodules had indeterminate findings in CUS, the elasticity was significantly different between malignant and benign nodules.