The thyroid gland is a lobulated structure located in the lower neck, in front of the trachea, with the right and left lobes close together on either side of the trachea and a thin ring of thyroid tissue connecting the left and right lobes called the “isthmus” in the middle. Thyroid imaging and detection rates are related to the diagnostic imaging modality. Ultrasound: Normal thyroid tissue on ultrasound is uniformly echogenic, and the anterior and posterior diameters of the isthmus generally do not exceed 3 mm. 19% to 67% of thyroid nodules are detected on ultrasound. CT: The thyroid gland is uniformly dense on plain CT, with a CT value of 80-100 HU. On enhanced CT, the thyroid tissue is uniformly and markedly enhanced, but it is important to note that the use of iodine contrast can cause abnormal iodine uptake in the thyroid gland for 4-8 weeks, which should be considered if one is planning to undergo thyroid nuclide testing or 131I therapy. MR: In MR images, the signal of the thyroid tissue is slightly higher than the signal of the adjacent muscle, similar to enhanced CT. enhanced MR images have uniform and consistent enhancement of the thyroid. Ultrasound is the preferred method of thyroid examination because of the superficial location of the thyroid gland, which facilitates ultrasound observation. 19% to 67% of thyroid nodules are detected by ultrasound, and in addition, ultrasound is easy and inexpensive to perform. 9% of thyroid nodules are detected by CT and MRI, and nodules found on CT and MRI are still selected for further examination by ultrasound. Nuclear imaging: The concentration of uptake in the right and left lobes of the thyroid gland is symmetrical, if the local concentration is “hot” nodules, and if it is reduced, it is “cold” nodules, and if the level of thyrotropin-releasing hormone is analyzed, if the nodules are hot and the level of thyrotropin-releasing hormone is reduced, the nodules are “hot” nodules. If a hot nodule is associated with hypothyroidism, it is very unlikely to be malignant and does not require further ultrasound or FNAB. Cold nodules are 10-20% likely to be malignant. 131I: 131I is useful for an overall evaluation of the remaining portion of the gland after thyroidectomy or ablation or for the presence of metastases. PET-CT: In PET-CT, the detection rate of thyroid nodules is 2-3%, and both benign and malignant nodules show increased FDG uptake relative to normal thyroid tissue. 14-40% of nodules with increased FDG uptake may be malignant, so further ultrasound and FNAB are still needed to clarify the diagnosis.