The Value Of Uitrasonic Elastography In Differential Diagnosis Of Thyroid Benign And Maliganant Nodules

Objective:To investigate the best cut-off point of strain ratio for diagnosis of thyroid cancer,To authenticate the diagnositic standard of Itoh5 elasticity score method;To compare the advantage of Itoh5 elasticity score method and the strain ratio method in diagnosis of thyroid cancer.Methods:191 patients with 278 nodules were examined by Itoh5 elasticity score method and the strain ratio method of ultrasonic elastograpy (UE) with TOSHIBA-SSA790A Color Doppler ultrasonography. The area under the curve(AUC) and cut-off point, both of which were obtained by using a receiver operating characteristic curve(ROC) analysis and according to the Youden index (sensitivity+specificity-1), were used to assess diagnositic performance. Statistical analysis of strain rate in diagnosis benign and malignant nodules was performed with line a=0.01 level T-test. Statistical analysis of sensitivity, specificity, accuracy between the two methods was performed with x2-test. Statistical analysis of AUC between the two methods for Z-test. All the statistical analysis in this study were carried out with SPSS13.0.Results:The biopsy of 191 patients with 278 noduless thyroid nodule showed:195 benign nodules, the majority of which is nodular goiter,69.7% (136/195).It was showed a large number of follicles and colloid by pathology. Other types of benign tumor-like pathological lymphocyte proliferation, thyroid adenoma, lymphocytic thyroiditis, nodular goiter with adenoma, atypical hyperplasia; 83 malignant nodules, the vast majority of which is papillary carcinoma,95.2% (79/83). During the pathology associated psammoma. In addition,3 cases is thyroid follicular cell carcinoma and 1 case is medullary thyroid carcinoma.(1) strain ratio method:the strain rate of benign nodules is 0.39-6.84 (3.19±1.36);the strain ratio of malignant nodules is 1.56-12.43 (7.33±2.21). Strain rate of malignant thyroid nodules was significantly higher than benign nodules. There was statistically significant (p <0.01). All possible strain ratios as the cut-point were calculated,then making ROC curve by sensitivity as the vertical axis and (1-specificity) as the abscissa. The beginning part of the curve rised more steeply, indicating a more accurate test resolution; while the area under the curve (AUC) was 0.939, indicating high diagnostic accuracy; area under curve compared with Az=0.5,there was statistically significant; According to the sensitivity and specificity, calculate the Youden index, select the most critical point as the cut-off point. Then determine the Strain Ratio 4.97 for the best diagnostic cut-off point.188 thyroid nodules Strain Ratio <4.97,90 nodules Strain Ratio> 4.97.176 thyroid nodules of the benign group thyroid nodules (195) in all 278 nodules Strain Ratio<4.97 and was coincidence with pathological diagnosis,19 nodules was not; 71 thyroid nodules of the malignant group (83) Strain Ratio≥4.97 Strain Ratio and was coincidence with pathological diagnosis,12 nodules was not. Strain Ratio 4.97 was the standard in differential diagnosis of benign and malignant thyroid nodules. The sensitivity was 85.5%,the specificity was 93.6%, the accuracy was 88.8%.(2) Itoh5 elasticity score method:score 1,2,3,4,5 as the cut-point were calculated respectively,then making ROC curve by sensitivity as the vertical axis and (1-specificity) as the abscissa. Area under the curve (AUC) was 0.896, indicating high diagnostic value, compared with Az=0.5,there was statistically significant; According to each possible score calculate sensitivity and specificity,and then calculate Youden index.They were 0.118,0.227,0.677,0.515,0.000 respectively. It can be seen, score 3 points was the most appropriate diagnostic cut-off point, namely, the benign nodules'score< 3,and malignant benign nodules' score> 3. It validated the diagnostic standard produced by professor Itoh in Japanese University of Tsukuba[II] The study consequence of elasticity score method showed 152 benign thyroid nodules elasticity score≤3; 126 thyroid nodules elasticity score > 3.146 thyroid nodules of the benign group thyroid nodules (195) in all 278 nodules elasticity score< 3. and was coincidence with pathological diagnosis,49 nodules was not; 77 thyroid nodules of the malignant group (83) elasticity score> 3. and was coincidence with pathological diagnosis,6 nodules was not. elasticity score 3 was the standard in differential diagnosis of benign and malignant thyroid nodules. The sensitivity was 92.8%,the specificity was 74.9%, the accuracy was 80.2%.(3) Comparison of two methods:the sensitivity of strain ratio method for diagnosis of benign and malignant thyroid nodules was increased 7.3% of that of elasticity score method, but there was no statistically significant (p> 0.05); the former specificity and accuracy was increased 15.3% and 8.6% of the latter respectively, there was statistically significant (p <0.01); Constructed ROC curve and calculate area under curve (AUC). Compare the two method with Az=0.5.there were statistically significant, indicating that the two diagnostic methods had high diagnostic value. The former increased 0.043,than the latter,but the statistical test Z=1.83, p=0.067> 0.05. Although there was statistically significant, the P is also close to 0.05. According to the foregoing analysis, Strain Ratio diagnostic value was higher than the elasticity scroe diagnosis..(4) misdiagnosis and missed diagnosis:In Itoh5 elasticity score method, elasticity score as a diagnosis standards of benign and malignant nodules,6 cases of missed diagnosis occured. Pathological types of thyroid were papillary carcinoma, (5) thyroid follicular cell carcinoma (1) respectively.49 misdiagnosed cases occurred. Pathologic types were nodular goiter, (44), thyroid follicular cell carcinoma (2), nodular goiter associated with Hashimoto's thyroiditis (3) respectively. In strain ratio method,4.97 as a diagnosis standards of benign and malignant nodules, there were 12 cases of missed diagnosis occurred. Pathological types of thyroid were thyroid papillary carcinoma (10), thyroid follicular cell carcinoma (2).19 misdiagnosed cases occurred. Pathological type were nodular goiter (15), thyroid adenoma (2), focal lymphocyte hyperplasia (2) respectively.Conclusion:1, Elasticity score method of thyroid ultrasonic elastography is helpful for differential diagnosis of thyroid benign and malignant nodules.2,The strain ratio can be more accurate and objective to reflect the relative hardness of the lesion. It may be a new and important standard in the diagnosis of benign and malignant thyroid nodules.3, The specificity and accuracy of strain ratio method as the cut-off points 4.97 was higher than Elasticity score method in differential diagnosis of thyroid benign and malignant nodules. There was statistically significant. The sensitivity difference had no statistically significant.