Ultrasound is preferred for thyroid disorders because it is real-time, precise, non-invasive and economical. With ultrasound, it is possible to find out: is there a problem with the thyroid? What is the problem? Does it require surgical intervention? Normal thyroid ultrasound performance: transverse section is butterfly or horseshoe shape, basically symmetrical, longitudinal section is long shuttle or long oval, envelope is smooth, clear boundaries, internal echoes are moderately strong, uniform distribution, and vascular echoes can be seen. Ultrasonographic manifestations of thyroid cancer: 1. Quantitative manifestations: the proportion of solitary cases is about 80%, and in a small number of cases, there are more than 2 and other benign nodules. Therefore, every nodule of the multiple foci should be carefully scanned to avoid leakage of diagnosis, especially the isthmus and upper and lower extremity margins of the thyroid isthmus, which are the easy to be missed by ultrasonographic examination, so attention should be paid to the up and down movement and the left and right lateral movement of the probe, and a comprehensive and careful scanning should be made. Boundary, morphology, internal echogenicity: the morphology is mostly irregular, the boundary is rough, blurred, burr-like changes, and the interior is mainly solid uneven low echogenicity, usually without peritoneum. 3, no nodule peripheral halo: ultrasound image of the peripheral halo of the thyroid nodule, refers to the hyperechoic band around the nodule, for the peripheral membrane of the thyroid nodule or the thyroid parenchyma or blood vessels under pressure. If the periphery of the nodule has a complete and regular halo, the likelihood of benign is high (studies have shown that the likelihood of the nodule being benign at this point is 12 times higher than the likelihood of malignancy); even if the periphery has an incomplete halo, the likelihood of benign is still 4 times higher than the likelihood of malignancy. 4, Aspect ratio A/T: benign nodules are generally elliptical or long elliptical in shape and A/T is mostly <1, while A/T of thyroid cancer is mostly ≥1, and A/T with a value of 1 can be used as one of the diagnostic bases for determining the benignness of the lesion. 5.Microcalcified foci: more than half of the foci have point-like or gravel-like microcalcified foci (≤1mm in diameter), scattered or clustered distribution. The pathological mechanism of microcalcified foci is due to the insufficient blood supply of tumor cells, which leads to necrosis and degeneration of tissues, accompanied by the deposition of calcium salts; microcalcification is of great value in the ultrasound diagnosis of thyroid cancer, and it is a characteristic manifestation of thyroid cancer. 6.Whether there is liquefied area in the lesion: The presence or absence of liquefied area can be an important indicator for identifying the benign or malignant nature of thyroid nodules. 7, Posterior echo attenuation: the tissue density of thyroid cancer is greater than that of the surrounding tissues, and the ultrasound energy absorption is more than that of the normal structure and benign nodules, which is also one of the indicators to identify benign and malignant. 8, Elasticity coefficient: Because the hardness of thyroid cancer tissues is large, the elasticity is relatively small, the strain rate is low, and the coefficient is more than 4 (3.3). Some scholars have confirmed that ultrasound real-time elasticity imaging has a high diagnostic value for thyroid nodules, and its diagnostic sensitivity, specificity, and accuracy for nodules have reached 94%, 86%, and 91%, respectively. 9. Characteristics of lesion blood flow distribution: Color Doppler blood flow imaging of thyroid cancer lesions is characterized by type II blood flow distribution (peripheral irregularity), which is related to the sensitivity of the instrument used, parameter adjustment and experience of the examiner, and is non-specific. The metastatic pattern of thyroid cancer is generally primary foci → zone VI lymph nodes → zone IV lymph nodes → distant metastasis, so ultrasonography should pay special attention to the situation of zone VI lymph nodes, which provides an important basis for the diagnosis and staging of thyroid cancer. Literature reports that although the diameter of the primary lesion is ≤10mm, the incidence of metastasis in the central lymph nodes (Zone VI) is still as high as 50%-70%, and the recurrence rate of lymph nodes after surgical resection is 5-20%. Ultrasonographic diagnosis of thyroid cancer should rely on the comprehensive judgment of multiple characteristic indexes of ultrasound images, such as hypoechoic nodules, rough edges, irregular morphology, A/T ≥1, internal microcalcification, posterior echo attenuation, poor elasticity, and abnormalities of cervical lymph nodes should be highly suspected to be malignant nodes; in the case of multiple nodules, every thyroid nodule should be carefully swept and analyzed during ultrasonographic examination. If malignant lesions are suspected, close follow-up should be carried out, and ultrasound-guided puncture biopsy pathology should be performed to clarify the diagnosis when necessary. Pathologic types of thyroid cancer are: 1. Papillary carcinoma: accounting for 60-70%, 10-year survival rate after operation＞90%. 2.Follicular carcinoma: accounting for 20%, more common in middle-aged and old women. 3.Medullary carcinoma: accounting for 2-5%, undifferentiated carcinoma: accounting for about 5%, with short course, high metastatic rate, and survival period of only a few months. Cervical lymph node zoning and monitoring play a key role in staging thyroid cancer, formulating surgical plan and evaluating prognosis!