| The thyroid secretes a variety of substances and plays a very important role in the human body.With the increase of people's physical examination awareness,more and more people take the initiative to participate in the physical examination,therefore,the detection rate of thyroid nodules is increasing day by day.The patients with early thyroid cancer without lymph node metastasis had a better prognosis.Lymph nody excision should be performed at thyreoidectomy when cervical lymph node metastasis occurred,the surgical incision will significantly increased,and these will affect severely the patient's appearance.The patients suffer from not only physical trauma,but also psychological stress and economic stress.Even some small papillary carcinoma could have lymph node metastasis in the early stages,so early diagnosis of thyroid cancer is particularly important.Ultrasound is the preferred imaging method for thyroid disease examination for easy operating,high resolution,low price,no radioactivity and higher diagnostic accuracy.However,the conventional ultrasound imaging model has its own insurmountable limitation,namely the operator dependence,therefore,a new effective ultrasound imaging method for identifying benign and malignant nodules is needed.The hardness of the tissue can reflect the properties of the thyroid nodules to a certain extent,generally,the malignant nodules are stiffer than the benign nodules.At present,ultrasound elastography is a relatively mature medical imaging mode,which reflects the hardness of the tissue by measuring the deformation of the tissue under pressure.Early ultrasound elastography use the external pressure or the pulsation caused by the body's own organs as pressure.The tissue produces distortion after being pressed and the elastic strain image appears on the screen of the ultrasonic instrument.The elastic images were graded according to degree of strain or the strain ratio(SR) between thyroid gland and the nodule was calculated.At present,acoustic radiation force impulse image(ARFI)is one of the research hotspots of ultrasound elastography,which includes the qualitative diagnosis of virtual touch tissue imaging(VTI)and the quantitative diagnosis of virtual touch tissue quantification(VTQ).ARFI imaging reduce the operator's dependence because the high-intensity acoustic pulse emitted by ultrasonic probe is used as external forces.From initial instantaneous elastography to later real-time elastography.Elastography from the initial manual compression and use one's own breathing or pulse compress tissue to create deformation to use acoustic pulse to compress tissue to create deformation.The repeatability of elastography is getting higher and higher through continuous technical improvement.Ultrasound elastography has a high diagnostic value for thyroid nodular disease.Previous studies have focused on the accuracy,sensitivity and specificity of thyroid cancer diagnosis with external pressure elastography scores or grades or strain ratio.This study will explore the diagnostic ability of ARFI imaging for thyroid nodules,compare with conventional ultrasound and stain ratio method of real time elastography,and combine with them,try to find out the best way to diagnose thyroid cancer.The pathological results were used as a reference standard,172 cases patients with thyroid nodules were examined by conventional ultrasound before operation from March 2014 to September 2014,in addition,128 cases patients with thyroid nodules were examined by conventional ultrasound,strain elastography and ARFI before operation from October 2014 to March 2015.Evaluate and compare the diagnostic capability of conventional ultrasound,strain ratio method of strain elastography and ARFI for thyroid nodules.The contents of this study include:(1)The diagnostic value of conventional high frequency gray scale ultrasound for thyroid nodules.(2)The value of acoustic radiation force impulse image in differentiating benign from malignant thyroid nodules.(3)Comparison of acoustic radiation force impulse imaging and strain elastography in differentiating malignant from benign thyroid nodules.Part one The Diagnostic Value of Conventional High Frequency Gray Scale Ultrasound for Thyroid NodulesObjective: This study mainly explored the diagnosis value of high frequency gray scale ultrasound for benign and malignant thyroid nodular disease.Methods: From March 2014 to September 2014,172 cases patients with 316 thyroid nodules were observed before operation in this study.The size,shape,echo type,boundary,aspect ratio,microcalcification and calcification type of the nodules were record.The diagnostic criteria of conventional high frequency gray scale ultrasound for benign and malignant thyroid nodules is as follows: the benign nodules are characterized by middle echo and high echo,regular shape,well defined boundary,no microcalcification and aspect ratio less than or equal to 1;the malignant nodules are characterized by low echo,very low echo,irregular shape,unclear boundary,internal microcalcification and aspect ratio greater than 1.Thyroid nodules with 3 or more malignant features were diagnosed as malignant nodules.Multivariate logistic analysis was performed for ultrasonographic features of thyroid carcinoma.Results: 1.There were statistical significance between benign and malignant thyroid nodules in shape,boundary,echo,aspect ratio,calcification type and age of patients(all P<0.001).2.Two-dimensional sonographic features such as irregular shape,unclear boundary,extremely low echo and aspect ratio greater than 1 were significantly associated with thyroid malignant nodules(all P<0.001).However,calcification type had no significant correlation with thyroid cancer.Aspect ratio greater than 1 is the strongest independent predictor of thyroid cancer(OR: 35.648;95%CI: 7.327-173.425),extremely low echo(OR: 23.492;95%CI: 3.231-170.792),unclear boundary(OR: 23.269;95% CI: 6.338-85.431),and irregular shape(OR: 10.596;95%CI: 3.784-29.676)are followed.3.The sensitivity,specificity,accuracy,positive predictive value,negative predictive of conventional high frequency gray scale ultrasound diagnosis for thyroid caner was 93.88%,96.45%,95.25%,95.83%,94.77%,respectively.Part two The Value of Acoustic Radiation Force Impulse Image in Differentiating Benign from Malignant Thyroid NodulesObjective: This study aimed to explore the diagnosic value of the grading method of VTI image,VTI image and two-dimensional gray scale image area ratio(AR)method,shear wave velocity(SWV)method,and the shear wave velocity of nodules and shear wave velocity of normal thyroid gland ratio(shear wave velocity ratio,SWR)method for differentiating benign from malignant thyroid nodules.Methods: From October 2014 to March 2015,128 cases patients with thyroid nodules were observed before operation and 152 thyroid nodules were analyzed in this study.Conventional ultrasound,VTI and VTQ were performed for the patients,VTI images were graded,area ratios and shear wave velocity ratios were calculated.According to the black and white proportion of the VTI images of thyroid nodules,the images were divided into six grades.Grade ?,all or most of the nodules are white(black proportion,0%–20%).Grade?,The nodules mainly appear in white with a small amount of black(black proportion,20%–40%).Grade ?,The nodules show similar percentages of black and white(black proportion,40%–60%).Grade ?,The nodules mainly appear in black with a small amount of white(black proportion,60%–80%).Grade ?,most of the nodules are black(black proportion,?80%).Grade?,all of the nodules are black(black proportion,100%)?The VTI images of all thyroid nodules were graded by two other sonographers respectively.The consistency of inter-observer about VTI grade was evaluated by the weighted kappa test.The consistency is very poor when ? < 0.20,the consistency is poor when ?= 0.21-0.40,the consistency is moderate when ?=0.41-0.60,the consistency is good when ?=0.61-0.80,the consistency is very good when ?= 0.81-1.00.Results:1.VTI images of the malignant nodules 72.73%(40/55)showed grade ?–?,whereas only 10.31%(10/97)of the benign nodules showed grade ?–?,and this difference was significant(P<0.001).2.The median of VTI grade for the malignant nodules were grade ?(95% confidence interval,CI 4.00-4.00),and the median of VTI grade for the benign nodules were grade ?(95% CI 2.00-2.00).The median of AR for the malignant nodules were 1.24(95% CI 1.10-1.27),and the median of AR for the benign nodules were 0.93(95% CI 0.88-0.98).The median of mean SWV for the malignant nodules were 3.54 m/s(95% CI 3.19-3.91),and the median of mean SWV for the benign nodules were 2.25 m/s(95% CI 2.12-2.43).The median of mean SWR for the malignant nodules were 1.70(95% CI 1.55-2.04),and the median of mean SWR for the benign nodules were 1.1(95% CI 1.05-1.17).The median of VTI grade,AR,mean SWV and mean SWR for the malignant nodules were significantly higher than those for the benign nodules(all P<0.001).3.Receiver operator characteristic(ROC)curve analyses showed that the best cutoff of VTI grade for predicting malignant nodules was greater than or equal to grade ?,the corresponding sensitivity,specificity,accuracy,positive predictive value,negative predictive was 72.73%,89.69%,83.55%,80.00%,85.29%,respectively.ROC curve analyses showed that the best cutoff of AR for predicting malignant nodules was 1.06,the corresponding sensitivity,specificity,accuracy,positive predictive value,negative predictive was 81.82%,79.38%,80.26%,69.23%,88.51%,respectively.ROC curve analyses showed that the best cutoff of SWV for predicting malignant nodules were 2.87m/s,the corresponding sensitivity,specificity,accuracy,positive predictive value,negative predictive was 78.18%,83.51%,81.58%,72.88%,87.10%,respectively.ROC curve analyses showed that the best cutoff of SWR for predicting malignant nodules was 1.36,the corresponding sensitivity,specificity,accuracy,positive predictive value,negative predictive was 83.64%,78.35%,80.26%,68.66%,89.41%,respectively.The area under the ROC curve(AUC)for VTI grade,AR,mean SWV and mean SWR was 0.854 (95% CI 0.788-0.906),0.860(95% CI 0.795-0.911),0.869(95% CI 0.805-0.918)and 0.853(95% CI 0.786-0.905),respectively,there was no significant difference(P>0.05).4.The results of interobserver agreement for VTI grade were as follow: the ? value was 0.98 and the 95% CI was 0.959-1.000(P<0.001).Part three Comparison of Acoustic Radiation Force Impulse Imaging and Strain Elastography in Differentiating Benign from Malignant Thyroid NodulesObjectives: This study aimed to evaluate the diagnostic value of acoustic radiation force impulse(ARFI)imaging and strain elastography in differentiating benign from malignant thyroid nodules.Methods: From October 2014 to March 2015,128 cases patients with thyroid nodules were observed and 152 thyroid nodules were analyzed before operation in our hospital.Conventional ultrasound,VTI grade,VTQ and SR were performed for all patients.The pathological result was the diagnostical standard,and the diagnostic performances of the 3 elastography analysis methods were analyzed and compared by multiple receiver operating characteristic curve analysis.The diagnostic performance of each independent elastography analysis method was expressed as the area under the receiver operating characteristic curve(AUC).The diagnostic performance was regarded as low(AUC=0.5-0.7),moderate(AUC=0.7-0.9),or high(AUC>0.9).Results: 1.The median of VTI grade,mean SWV and mean SR for the malignant nodules were grade ?(95% CI 4.00-4.00),3.54 m/s(95% CI 3.19-3.91)and 3.68(95% CI 3.09-4.10),respectively.The median of VTI grade,mean SWV and mean SR for the benign nodules were grade ?(95% CI 2.00-2.00),2.25 m/s(95% CI 2.12-2.43)and 1.42(95% CI 1.20-1.79),respectively.The median of VTI grade,mean SWV and mean SR for the malignant nodules were significantly higher than those for the benign nodules(all P<0.001).2.ROC curve analyses showed that the best cutoff of VTI grade for predicting malignant nodules was greater than or equal to grade ?,the corresponding sensitivity,specificity,accuracy,positive predictive value,negative predictive was 72.73%,89.69%,83.55%,80.00%,85.29%,respectively.The best cutoff of SWV for predicting malignant nodules were 2.87m/s,the corresponding sensitivity,specificity,accuracy,positive predictive value,negative predictive was 78.18%,83.51%,81.58%,72.88%,87.10%,respectively.The best cutoff of mean SR for predicting malignant nodules was 2.37,the corresponding sensitivity,specificity,accuracy,positive predictive value,negative predictive was 90.91%,74.23%,80.26%,66.67%,93.51%,respectively.The AUC of VTI grade,mean SWV and mean SR was 0.854(95% CI 0.788-0.906),0.869(95% CI 0.805-0.918)and 0.849(95% CI 0.782-0.902),respectively,the comparison of the three used the Z test,there was no significant difference(P>0.05).3.The sensitivity,specificity,and accuracy of conventional ultrasound features for differential diagnosis between malignant and benign thyroid nodules was 87.27%(95% CI 69.61-91.25),94.85%(95% CI 88.39-98.31),and 92.11%(95% CI 86.62-95.86),respectively.4.The accuracies of mean SWV and mean SR were inferior to that of conventional ultrasound,whereas there was no significant difference between VTI grade and conventional ultrasound.5.Seven malignant nodules were misclassified as benign nodules by conventional ultrasound,but the number of misdiagnoses decreased to 1,2,or 0 when conventional ultrasound combined with VTI grade,mean SWV and mean SR,respectively.Five benign nodules were misclassified as malignant nodules by conventional ultrasound,and the number of misdiagnoses decreased to 2 when conventional ultrasound combined with VTI grade;however,this number did not change for conventional ultrasound combined with mean SWV or mean SR.The combined application of conventional ultrasound and different elastography analysis methods further improved the accuracy compared with conventional ultrasound,although the differences were not significant(P>0.0083,Bonferroni correction).Conclusions: 1.Irregular shape,unclear boundary,very low echo,internal microcalcification,aspect ratio greater than 1 were typical ultrasonographic features of thyroid carcinoma.Aspect ratio greater than 1 is the strongest independent predictor of thyroid cancer.Its specificity is higher but its sensitivity is too low.2.The direct evaluation method of ARFI(including VTI grades and mean SWV)and the indirect evaluation method of ARFI(including AR and SWR)can effectively differentiate benign from malignant thyroid nodules.3.ARFI imaging and the mean SR method of strain elastography exhibited approximately equal value in distinguishing benign from malignant thyroid nodules.When the malignant characteristics of thyroid nodules are not obvious and they have no typical benign characteristics at the same time: the nodules are solid low echo or extremely low echo,internal echo uniform or non-uniform,regular shape,well defined boundary,no obvious envelope,no obvious microcalcification,or with peripheral or internal coarse calcification,on the basis of conventional ultrasound,it is helpful in differentiating benign and malignant thyroid nodules by combining with ARFI or SR elastography. |
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