Ultrasound, CT, and MRI are commonly used imaging tests in medicine. Generally speaking, CT and MRI are indeed more advanced and better than ultrasound and can provide more information to help doctors make a diagnosis. However, each imaging test has its own advantages and shortcomings, and it is important to choose the right test for different organs rather than just the advanced one. The first choice for thyroid nodule screening is ultrasound. Because of its superficial location, the thyroid gland is well suited for ultrasound. ultrasound is useful for thyroid nodules that cannot be palpated during a physical examination and in cases where thyroid palpation is unsatisfactory. Ultrasound examination can determine whether the nodule is single or multiple, cystic, solid or mixed, whether the echogenicity of the nodule is uniform, whether the edges are smooth, whether there is an envelope and whether the envelope is intact, whether there is calcification within the nodule and the nature of the calcification, whether there is blood flow and whether there is abundant blood flow, and the relationship between the thyroid and adjacent tissues such as the carotid artery and jugular vein. Ultrasound examinations can be used for follow-up and observation during medical treatment of thyroid disease and after surgery to find out whether there is local recurrence of metastasis. Ultrasound is now used as the first choice for routine thyroid examination. CT examination cannot reliably identify the benignity or malignancy of thyroid nodules, so it is usually not the first choice for imaging thyroid nodules, and is only done when the following cases are encountered: suspicion of lung metastases from thyroid cancer, and identification of thyroid metastases from esophageal cancer; preparation for thyroid surgery, especially in cases of reoperation of the thyroid gland, to understand the residual thyroid gland, and to assess the relationship between the thyroid gland and the surrounding tissues. As with CT, magnetic resonance imaging (MRI) is not usually the preferred method of imaging the thyroid. The disadvantages of MRI are that due to the special structure of the head and neck organs, with cavernous organs such as the nasopharynx, oropharynx, larynx and sinuses, artifacts are easily produced, and physiological movements such as swallowing, breathing, and large blood vessel pulsations can cause distorted images, and MRI is not comparable to ultrasound in determining the nature of nodule calcification, plus the examination is expensive, so MRI is generally not considered. Therefore, for most thyroid nodules, ultrasound is the first choice for routine examination. For some thyroid cancers, CT or MRI can be chosen on the basis of ultrasound if necessary to determine the size of the tumor, the relationship with adjacent organs, whether there are lymph node metastases, airway compression obstruction, lung metastases, etc., or to clarify the extent of retrosternal nodular goiter, depending on the specialist’s opinion.