Characteristics Of Time-intensity Curve On Contrast-enhanced Ultrasound For Benign And Malignant Thyroid Nodules

Objective: To assess the characteristics of time-intensity curve(TIC)on contrast-enhanced ultrasound(CEUS)for benign and malignant thyroid nodules.Materials and Methods: We retrospectively reviewed the patients with diagnosis of thyroid nodules,which were scanned by CEUS from July 2014 to August 2015.Written informed consent was obtained from all patients before CEUS.The inclusion criteria were: the nodules underwent CEUS based on conventional ultrasound(US);final diagnosis was confirmed by pathology after surgical excision or cytology after Fine Needle Aspiration(FNA,combined with conventional US results).Exclusion criteria included: the amplitude of the respiratory motion is too sharp to compensate;the solid part of the nodule was too small to be analyzed;the size of the nodules were too large that the plane of CEUS couldn't show the entire nodule and its surrounding thyroid gland at the same time.Finally,103 thyroid nodules from 98 patients were included.The histology by surgical excision or cytology by FNA(combined with conventional US results)finally confirmed that 76 malignant(Papillary carcinoma was diagnosed in 75 nodules,follicular carcinoma in 1,)and 27 benign nodules(nodular goiter in 12,chronic lymphocytic thyroiditis in 11,thyroid adenoma in 4)were included.The dynamic contrast-enhanced images were saved in DICOM format from the machine's hard disk and input into Tom Tec software(Tom Tec Gmb H,Munich,Germany),which could draw TIC for quantitative analysis.Manually designed regions of interest(ROI)were separately drawn in solid part of the nodule and the peripheral thyroid parenchyma.The TICs were assayed for the following indices: 1.Perfusion parameters:(1)Peak intensity(PI),defined as the maximal signal intensity measured in the selected ROI(the PI of peripheral thyroid parenchyma was defined as 100%);(2)Rise time(RT),defined as the time that the curve increase from the starting point to the 50% of the peak;(3)Time to peak(TTP),defined as the time from the starting point to the PI of the curve;(4)Area under the rising curve(AUCR),defined as the area under the rising part of the curve;(5)The maximum slope coefficient of the wash-in curve(MSCWI),defined as the maximum slope coefficient of the rising curve.2.Clearance parameters:(1)The maximum slope coefficient of wash out curve(MSCWO),defined as the maximum slope coefficient of the falling curve;(2)Area under the falling curve(AUCF),defined as the area under the falling part of the curve.3.Comprehensive parameters:(1)Mean transit time(MTT,in seconds),defined as the time from the starting point to the PI drop to 50% of the curve;(2)Area under the curve(AUC),defined as the area under the whole time intensity curve.The relative values(RV)of PI(?PI)were calculated by subtracting the signal intensity measured in the peripheral parenchyma,when the signal intensity in the nodule reached the PI,from the PI in the nodule;the RV of RT(?RT),TTP(?TTP),MTT(?MTT),MSCWI(?MSCWI),MSCWO(?MSCWO),AUC(?AUC),AUCR(?AUCR),and AUCF(?AUCF),were calculated by subtracting the values in the peripheral parenchyma from the values in the nodules respectively.The statistical analyses were performed using the SPSS 13.0 statistical package.Quantitative variables were expressed by the mean with standard deviation.Comparisons between two groups were performed with the T-Student test and among three groups were performed with one-way ANOVA.All differences with a P value of less than 0.05 were considered significant.Results: Compared with benign thyroid nodules,the characterization of TIC on CEUS in malignant nodules could be a lower ?PI(25.82±9.26,-11.13±9.08),later ?RT(-0.32±0.23,0.31±0.47)and ?TTP(-0.44±0.18,0.38±0.52),gentler ?MSCWI(5.72±2.81,-3.69±4.93),smaller ?AUCR(74.02±21.13,-89.80±23.00)in perfusion parameters,a smaller ?AUCF(111.91±25.51,-81.72±29.36)in clearance parameters and a smaller ?AUC(185.93±35.23,-171.52±38.97),an earlier ?MTT(2.10±1.18,-1.69±1.20)in comprehensive parameters(P<0.05).Compared with malignant nodules(<1cm),the characterization of TIC on CEUS in malignant nodules(?1cm)could be a higher ? PI(-14.72±7.29,-1.07±5.22),earlier ? RT(0.53±0.27,-0.30±0.31)and ? TTP(0.67±0.2,-0.43±0.17),steeper ? MSCWI(-6.19±2.73,3.32±2.13)in perfusion parameters,a larger ? AUCF(-91.19±27.00,-55.21±17.02),steeper ?MSCWO(2.16±1.33,-2.07±1.77)in clearance parameters and a larger ? AUC(-182.88±37.60,-139.72±21.37),earlier ? MTT(-1.52±1.08,-2.17±1.42)in comprehensive parameters(P<0.05).Conclusions: Characteristics of TIC on CEUS for malignant thyroid nodules are more pretend to be a higher ? PI,earlier ? RT and ? TTP,steeper ? MSCWI in perfusion parameters,a larger ? AUCF,steeper ?MSCWO in clearance parameters and a larger ? AUC,earlier ? MTT in comprehensive parameters.TIC on CEUS could present the different characteristics of benign and malignant nodules,which is a potential technique for differentiation.