Evaluation of inter-observers consistencyin differentiating diagnosis of thyroid nodules based on calculation of the strain ratio on thyroid sonoelastography

Abstract

Objective To investigate inter-observers consistencyin differentiating benign or malignant thyroid nodules by calculating strain ratio (SR).Methods Eighty-two thyroid nodules in 68 patients were examined with conventional ultrasound (US) and real-time elastography by three independent ultrasound doctors.SR of the nodule and the surrounding tissue was calculated.A 5-point confidence level was used to discriminate malignant from benign nodules by US and then by combined with SR.The diagnostic performances were evaluated by receiver operating characteristic (ROC) analysis.Results With combination of US and SR,the numbers of lesions with 3-point were less than US alone in all three doctors,while the numbers of 1-point and 5-point were increased apparently.A better inter-observers consistency was achieved in combination of SR and US,compared to US alone (k =0.715,0.734,0.803 versus 0.441,0.536,0.517,all P ＜ 0.05).The sensitivity,positive predictive value,and accuracy in three operators increased significantly when combined with SR (all P ＜ 0.05).ROC analysis revealed significant improvement in differential diagnosis between malignant and benign thyroid nodules with combination US and SR.The areas under the ROC curve were 0.929 at combined with SR and 0.835 at US for doctor 1,0.938 and 0.852 for doctor 2,and 0.917 and 0.840 for doctor 3(P ＜0.05,respectively).Conclusions As a novel semi-quantitative method,combination with the SR could help to improve differential diagnosis between benign or malignant thyroid nodules and was showed reliable interoperator consistency. Key words: Ultrasonography; Thyroid diseases ; Elasticity ; Strain ratio