Value Of Contrast-enhanced Ultrasound In Differential Diagnosis Of ACR TI-RADS Level 4-5 Benign And Malignant Thyroid Nodules Stratified By Size

Objective: Our study aimed to compare the conventional ultrasound(US)and contrast-enhanced utrasound(CEUS)features of ACR TI-RADS level 4-5 benign and malignant thyroid nodules with different sizes,and use random forest algorithm to calculate the relative importance of each feature based on its specificity.Finally we evaluate the value of CEUS in differential diagnosis of ACR TI-RADS category 4-5 benign and malignant thyroid nodules stratified by size.Methods: A total of 192 ACR TI-RADS level 4-5 thyroid nodules underwent FNA or surgery were included.There were 92 nodules less than 1 cm,63 nodules were 1-2cmand 36 nodules were more than 2cm.Difference comparison was used to compare the ultrasound features between benign and malignant nodules in each group.Random forest algorithm was used to rank the relative importance of each feature based on its specificity.Using ROC curve to evaluate the value of CEUS in differential diagnosis of ACR TI-RADS level 4-5 benign and malignant thyroid nodules stratified by size.Result: Of those <1cm,the differences of echogenicity,aspect ratio,margin and enhancement intensity between benign and malignant thyroid nodules were significant.Of those 1-2cm,the differences of aspect ratio,margin,enhancement intensity and enhancement homogeneity were significant while of those >2cm,the differences of enhancement mode and enhancement homogeneity were significant(P < 0.05).Of those <1cm,the order of feature relative importance was isoenhancement,aspect ratio < 1,well defined margin,hypoenhancement,hyperenhancement,poorly defined margin,aspect ratio ≥ 1.Of those 1-2cm,the order was well defined margin,aspect ratio < 1,hypoenhancement,isoenhancement,aspect ratio ≥ 1.Of those >2m,the order was rim enhancement,diffuse enhancement,homogeneous enhancement,heterogeneous enhancement,centrifugal enhancement and centripetal enhancement.Of those <1cm,the differences in diagnostic value between US and US+CEUS were not significant(AUC: 0.787vs0.808,P=0.103,sensitivity: 56.5%vs79.0%,specificity:87.1%vs74.1%,accuracy: 66.7%vs77.4%).Of those 1-2cm,the differences in diagnostic value between US and US+CEUS were significant(AUC: 0.789 vs 0.882,P=0.045,sensitivity: 85.0% vs97.5%,specificity:65.2%vs65.2%,accuracy:77.8%vs85.7%).Of those >2cm,the differences in diagnostic value between US and US+CEUS were significant(AUC: 825 vs 945,P=0.033,sensitivity: 70.0%vs90.0%,specificity: 81.2%vs87.5%,accuracy: 75.0%vs88.9%).Conclusions:(1)The features of US and CEUS have different diagnostic value in different sizes of thyroid nodules.(2)The features with higher specificity were as follows: isoenhancement,aspect ratio < 1 and well-defined margin(<1cm);welldefined margin,aspect ratio <1,and hypoenhancement(1-2cm);rim-like enhancement,diffuse enhancement and homogeneous enhancement(>2cm).(3)CEUS is suitable for the differential diagnosis of TI-RADS level 4-5 benign and malignant thyroid nodules with diameter ≥ 1cm,especially with diameter > 2cm.In clinical,we can combined US with CEUS to improve the accuracy of differential diagnosis of TI-RADS category 4-5 thyroid nodules with diameter ≥ 1cm.However,CEUS is not effective in the differential diagnosis of TI-RADS level 4-5 thyroid nodules with diameter < 1cm.