Applicative value of acoustic radiation force impulse imaging in differential diagnosis of small hypoechoic thyroid nodules

Abstract

Objective To investigate the applicative value of acoustic radiation force impulse imaging (ARFI) in the differential diagnosis of small hypoechoic thyroid nodules.Methods 31 patients were pathologically confirmed as having a total of 44 small hypoechoic thyroid nodules ≤ 1 cm in diameter,followed by analyses of the characteristics of their ARFI images,including virtual touch tissue imaging (VTI) and virtual touch tissue quantification (VTQ).Based on VTI images of the nodules,the hardness of small hypoechoic thyroid nodules was respectively scored,and the ratios of VTI images to gray scale image areas were calculated.With pathological diagnosis as the gold standard,VTI scores,area ratios and VTQ values of the ROC curve in diagnosis of thyroid malignant nodules were sketched so as to explore the optimal cut-off points in VTI scores,area ratios and VTQ values in the diagnosis of malignant nodules.Results By the ROC curve test,VTI score of 3 was determined as the cut-off point of areas ratio,with the sensitivity and specificity of diagnosing thyroid cancer being 96.0 ％ and 94.7％,respectively.There were 34 nodules with VTI score greater than 3 (including 9 benign nodules and 25 malignant nodules) and 10 nodules with VTI score of 3 or less (all benign nodules).Malignant thyroid nodules had higher ratio of VTI images to gray scale image area than that of the benign nodules (1.58 ± 0.18 vs 1.30 ± 0.10,P ＜0.05).When 1.47 was set as the cut-off point of areas ratio,the sensitivity and specificity of diagnosing thyroid cancer were 80.0％ and 94.7％,respectively.The VTQ value of 2.76 m/s in diagnosis of thyroid malignant nodules was designated as the cut-off point,with a sensitivity of 88.0 ％,specificity of 94.7 ％.Conclusions The ARFI technique is able to provide information of thyroid nodule hardness,which guarantees its high applicative value in the differential diagnosis of small hypoechoic thyroid nodules. Key words: Ultrasonography; Thyroid nodule ; Acoustic radiation force impulse imaging