[Abstract] Objective To investigate the differential diagnostic value of ultrasound gray-scale ultrasound and elastography and their combined application for benign and malignant thyroid nodules. Methods The preoperative gray-scale ultrasound and ultrasound elastography features of a total of 97 lesions in 73 patients with thyroid nodules were retrospectively analyzed, and the nodules were classified into five grades: benign, probably benign, indeterminate, probably malignant and malignant, respectively, and compared with pathological findings, and the diagnostic effect of the three was evaluated by applying the subject operating characteristic curve (ROC curve). Results The area under the ROC curve of thyroid nodules diagnosed by ultrasound elastography (0.806) was smaller than that of gray-scale ultrasound (0.890) (P<0.01), while the area under the ROC curve of thyroid nodules diagnosed by the combination of both (0.945) was larger than that of gray-scale ultrasound alone (P<0.05) or ultrasound elastography (P<0.01). Conclusion Ultrasound elastography can help the differential diagnosis of benign and malignant thyroid nodules by gray-scale ultrasound, and the combined application of both can significantly improve the diagnostic accuracy of thyroid cancer. [Ultrasonic Elastography (UE) is a new ultrasound technique developed in recent years, firstly proposed by Ophir et al. in 1991, which can be used to evaluate the hardness of tissues and lesions. Currently, ultrasound elastography is more frequently applied to determine the benignity and malignancy of breast and prostate masses, as well as the evaluation of the degree of atherosclerosis, and its value has been affirmed, but fewer studies have been reported on the application to thyroid nodules. In this study, gray-scale ultrasound and elastography features of a total of 97 thyroid nodules in 73 patients with pathological findings were retrospectively analyzed to evaluate the effect of both alone and in combination in determining the benignity and malignancy of thyroid nodules, with the aim of exploring the value of elastography in the differential diagnosis of benign and malignant thyroid nodules. 1, Materials and methods 1.1, General data, 73 patients with 97 thyroid nodules examined in our hospital from October 2009 to July 2010, including 52 females and 21 males, aged 24 to 72 years, with an average of (48.3±13.7) years. The size of the lesions ranged from (4.6×3.2) mm to (41.7×23.3) mm, with 49 on the left side of the thyroid, 41 on the right side of the thyroid, and 7 in the isthmus. All cases were diagnosed by surgical or ultrasound-guided puncture biopsy. 62 benign nodules, including 49 nodular goiter nodules, 6 adenomas, 4 Hashimoto's disease hyperplastic nodules, and 3 subacute thyroid inflammatory nodules, and 35 malignant nodules, all of which were papillary carcinomas. 1.2, Instruments and examination methods, The instruments were SIEMENS S2000 color Doppler ultrasound diagnostic instrument with probe model 14L5 and frequency 5-14 MHz. the patient was placed in a supine position with the pillow behind the neck padded back so that the neck was overextended and the examination site was fully exposed. The nodules were then subjected to ultrasound elastography with a sampling frame (i.e., ROI of the region of interest) larger than the extent of the lesion. For ultrasound elastography, the probe was placed lightly on the neck to ensure a close fit with the skin, and a QF value greater than 60 was observed on the ultrasound instrument display to obtain a more stable ultrasound elastogram and save the disk. The gray-scale ultrasound and ultrasound elastography of all nodules were analyzed offline by two ultrasound professional investigators respectively, and the diagnosis was completed and conclusions were drawn independently; for those who disagreed with each other, the two investigators agreed as the final conclusion after consultation; both the gray-scale ultrasound and ultrasound elastography investigators were unaware of each other's diagnostic results. 1.3. The criteria for determining gray-scale ultrasound, reference literature reports and clinical practice experience classify the gray-scale ultrasound performance of thyroid nodules into malignant features and benign features. Malignant features include irregular morphology, unclear border, aspect ratio greater than or equal to 1, internal hypoechoic, microcalcifications, posterior echogenic attenuation, etc.; benign features include regular morphology, clear border, aspect less than 1, internal isoechoic, hyperechoic, The features of benign include regular morphology, clear border, longitudinal and transverse less than 1, internal isoechoic, hyperechoic, with (or without) no echogenicity or coarse calcification, no posterior echogenic attenuation. The evaluation criteria were: those with the above benign features were judged as benign, those with less than 3 (including 3) benign features but no malignant features were judged as possibly benign, those between benign and malignant were judged as indeterminate, those with 1~2 malignant features were judged as possibly malignant, those with more than 3 (including 3) malignant features were judged as malignant; the diagnoses of benign, possibly benign, indeterminate, possibly malignant and malignant were recorded separately. The diagnostic results of benign, possibly benign, indeterminate, possibly malignant and malignant were recorded as 1, 2, 3, 4 and 5 points respectively. 1.4. Judgment criteria of elasticity imaging, SIEMENS S2000 color Doppler ultrasound diagnostic instrument elasticity imaging color-coded the hardness of tissues, and reflected the relative hardness of each tissue by different colors, from soft to hard as pink, purple, green, yellow and red, respectively. In this study, we synthesized the experience of ultrasound elastography in breast and thyroid nodules from domestic and foreign literature, and combined with the characteristics of color elastography of this instrument, we developed the following scoring and judgment criteria for ultrasound elastography of thyroid nodules: according to the different colors of nodules displayed in ultrasound elastography, they were scored as 1 to 5: 1, nodules are predominantly pink; 2, nodules are predominantly purple; 3, nodules are predominantly green; and For a score of 4, the nodules were predominantly yellow; for a score of 5, the nodules were predominantly red. A score of 1 was judged as benign, 2 as possibly benign, 3 as indeterminate, 4 as possibly malignant, and 5 as malignant. 1.5. Judgment criteria for the combined application of gray-scale ultrasound and elastography. If the scores of gray-scale ultrasound and elastography are the same, the score will be used as the combined application score; if they are not the same, the scores of the two methods will be summed and averaged. Judgment criteria: 1 and 1.5 points were judged as benign, 2 and 2.5 points were judged as possibly benign, 3 points were judged as indeterminate, 3.5 and 4 points were judged as possibly malignant, and 4.5 and 5 points were judged as malignant. 1.6. Statistical analysis was performed using MedCalc 11.2 software to calculate the sensitivity and specificity of gray-scale ultrasound, elastography and the combined application of both for the graded diagnosis of thyroid nodules, respectively. 2. Results 2.1. Graded diagnostic results, gray-scale ultrasound, elastography and the combined application of both on thyroid nodules were determined. Among the 97 thyroid nodules in this group, 11 (11.34%), 11 (11.34%) and 8 (8.25%) nodules could not be determined as benign or malignant by gray-scale ultrasound, elastography and the combined diagnosis of both, respectively. Of the 11 nodules for which gray-scale ultrasound could not determine the benignity or malignancy, elastography diagnosed 6 as possibly malignant or malignant, 3 as possibly amphoteric or benign, and 2 as indeterminate in nature. Of the 11 nodules whose benignity could not be determined by elastography, gray-scale ultrasound diagnosed 3 as possibly malignant or malignant, 7 as possibly conscientious or benign, and 2 as indeterminate in nature. And, of the 27 (27.84%) nodules diagnosed as malignant by elastography, 12 were diagnosed as malignant by gray-scale ultrasound, 2 could not be determined, and 13 were probably benign or benign. Elastography and gray-scale ultrasound are complementary, and their combined diagnosis of thyroid nodules reduces misdiagnosis. 2.2. Graded ROC curve results, gray-scale ultrasound, elastography and the combined application of both for grading determination of thyroid nodules ROC curve. The area under the ROC curve of thyroid nodules determined by elastography alone (0.806) was smaller than that of grayscale ultrasound alone (0.890) (Z=3.525, P<0.001), but the area under the ROC curve of thyroid nodules determined by the combination of both (0.945) was larger than that of grayscale ultrasound alone (Z=2.512, P=0.012) and elastography (Z=4.433, P<<< em="">0.001). 3. Discussion 3.1. The significance of gray-scale ultrasound for the diagnosis of thyroid nodules. With the widespread use of high-resolution ultrasound equipment in clinical practice, more and more palpable or nonpalpable thyroid nodules are being detected clinically. Cooper et al. showed that ultrasound detected the presence of thyroid nodules in 19-67% of a randomly selected population and that ultrasound was able to detect nodules as small as 1 to 3 mm. However, a variety of pathological conditions can lead to the formation of thyroid nodules, including malignant tumors and benign lesions (adenomas, hyperplasia, inflammatory disease, etc.), making accurate determination of the benignity or malignancy of thyroid nodules critical to the clinical selection of an appropriate treatment strategy. In this study, we evaluated the gray-scale ultrasound characteristics of 97 thyroid nodules, including morphology, borders, internal echogenicity, presence or absence of calcification and calcification pattern, and posterior echogenic changes, and found that the nature of some nodules could not be determined by gray-scale ultrasound in comparison with pathological findings, and the area under the ROC curve for the diagnosis of thyroid nodules by gray-scale ultrasound grading was 0.890. In order to better identify the benignity and malignancy of thyroid nodules In order to better identify the benignity and malignancy of thyroid nodules, the author combined grayscale ultrasound and elastography to evaluate the benignity and malignancy of thyroid nodules and compared the results with grayscale ultrasound and elastography alone. The principle of elastography is based on the fact that when human tissues are under certain pressure (pressure includes external and internal forces), the tissues will undergo different degrees of deformation due to differences in softness and hardness, and the ultrasound equipment uses autocorrelation techniques to analyze the RF signals generated before and after the tissue deformation to obtain the internal strain distribution of the corresponding tissues. The ultrasound equipment uses autocorrelation technology to analyze the RF signals generated before and after the tissue deformation to obtain the strain distribution within the corresponding tissues and color-code them to form a color elastogram for diagnosis. Malignant tissues are usually harder and less elastic, which is reflected by the elastogram. At present, both breast and a small number of thyroid ultrasound elastography studies have been performed using technologies provided by HITACHI or ESAOTE, both of which rely on the operator to apply a certain amount of external force to the tissue through the probe, and are therefore more compliant to the physician. In contrast, this study uses SIEMENS ultrasound elastography, which does not require the operator to apply external force to the probe and relies mainly on the mechanical excitation of the thyroid gland by internal factors (breathing, heartbeat, vascular pulsation, etc.) of the subject, so the elastogram of this technique is more stable and objective. 3.3. The significance of elastography for the diagnosis of thyroid nodules. In this study, ultrasound elastography of 97 thyroid nodules was graded for benignity and malignancy, and the results showed that the area under the ROC curve was 0.806, which was similar to the results of the study by Ping Zhou et al. However, of the 27 thyroid nodules judged as malignant by ultrasound elastography in this data set, only 18 (66.67%) were confirmed as thyroid cancer by final pathological results. The results showed that the larger the volume of the nodule, the lower the sensitivity and specificity of the nodule. All three benign nodules in this group were diagnosed as malignant on ultrasound elastography; third, the mechanical excitation of the carotid artery pulsation may differ significantly between different sites of thyroid nodules, and therefore may also have an impact on the elastography results. Although the results of this study showed that ultrasound elastography was less accurate than gray-scale ultrasound in diagnosing thyroid cancer, the ability of combined ultrasound elastography and gray-scale ultrasound to determine benign and malignant thyroid nodules was significantly greater than that of gray-scale ultrasound or ultrasound elastography alone. Among the 97 thyroid nodules in this group, the area under the ROC curve for the combined diagnosis of ultrasound-elastography and grayscale ultrasound (0.945) was greater than that for grayscale ultrasound alone (0.890) (Z=2.512, P=0.012) and ultrasound-elastography (0.806) (Z=4.433, P<< em="">0.001); moreover, the number of nodules whose nature could not be determined by the combined diagnosis was 8 (8.25%). was 8 (8.25%), which was lower than 11 (11.34%) for gray-scale ultrasound and 11 (11.34%) for ultrasound elastography alone. In conclusion, elastography can be a useful complement to gray-scale ultrasound in determining the benignity and malignancy of thyroid nodules, and their combined application can significantly improve the diagnostic accuracy of thyroid cancer. However, as a new ultrasound technique, the application of ultrasound elastography in thyroid lesions is still in the preliminary stage. The author believes that with the progress of ultrasound elasticity technology and the accumulation of clinical application experience, it has a good application prospect in the differential diagnosis of benign and malignant thyroid nodules.