The basic principle of nuclear medicine nuclide imaging is tracer technology, the conventional tracer for thyroid imaging is 99mTc, the tracer is taken up by the functional thyroid tissue, the location of the thyroid gland can be observed, the morphology, diffuse or limited lesions, is an important and indispensable examination for the diagnosis and treatment of thyroid diseases. I. Morphological abnormalities of the thyroid gland: normal thyroid gland becomes butterfly-shaped, there can be physiological variations such as horseshoe-shaped, etc. Sometimes goiter can form abnormal thyroid morphology. When the thyroglossal duct is not completely closed, the conus lobe located in the isthmus can be formed. Absence of one lobe of the thyroid gland or hypoplasia of one lobe is of clinical importance in thyroid surgery. In cases of one-lobe agenesis, where a nodule or tumor develops on the healthy side, the surgical approach and the effect on postoperative thyroid function should be evaluated before surgery. If the nodule is benign normal thyroid tissue should be preserved as much as possible, and it should be made clear to the patient that there is a possibility of postoperative hypothyroidism. If the absence of one lobe of the thyroid is not clarified preoperatively and a lobectomy of the tumor gland is performed, this can result in severe loss of thyroid function, without the patient’s knowledge, and should be considered medical malpractice. Even if the nodule is malignant, this should be made clear to the patient. Therefore, before any surgery of the thyroid gland, it is necessary to do nuclear imaging of the thyroid gland to clarify the morphological characteristics of the thyroid gland, which is helpful to help formulate the surgical plan and avoid unnecessary disputes between doctors and patients. Second, the location of the thyroid gland is abnormal: 16 to 17 days of gestation, the embryonic anterior pharyngeal layer cells form the thyroid protoplasm, move down to form the thyroglossal ducts, and expand into the thyroid cell mass. In the 7th week of gestation, the final position of the thyroid gland is reached in the anterior inferior part of the trachea. the thyroid shape is formed in the 8th to 9th week. If there is any residual thyroid tissue during migration, then lingual thyroid, thyroglossal cysts, and thyroid conus lobes may form. Such lesions are characterized by the coexistence of normal and ectopic thyroid tissue, with the conical lobe of the thyroid gland being more common. Ectopic thyroid glands are formed when thyroid tissue migrates to any abnormal site along the migratory path of embryonic thyroid tissue between the base of the tongue and the posterior sternal mediastinum, e.g., the root of the tongue thyroid gland, the paratracheal thyroid gland, the anterior cervical subcutaneous thyroid gland, and the retrosternal thyroid gland. Such lesions are characterized by the presence of ectopic thyroid glands without normal thyroid glands. The cause of congenital hypothyroidism in neonates is ectopic thyroid in about 1/3 of cases. In cases of neonatal hypothyroidism, nuclear thyroid imaging should be performed promptly to clarify whether the thyroid is ectopic or not, and if the diagnosis is confirmed, protection should be provided to avoid damage. In some cases, the ectopic thyroid gland is well developed, and there is no manifestation of hypothyroidism. With the increase of age, the thyroid gland enlarges, forming a mass at the base of the tongue, a paratracheal mass, a subcutaneous mass in the anterior neck, and a retrosternal mass, etc. If surgical excision is performed, the thyroid gland will be removed. If surgical resection is performed according to the swelling, it can cause complete loss of thyroid function with serious clinical consequences. Therefore, if a mass is found at the base of the tongue, the anterior neck, or the posterior sternum and is to be operated on, it is necessary to do a thyroid nuclear imaging before the operation in order to clarify whether it is an ectopic thyroid gland or not. If the mass is ectopic and the normal thyroid is absent, the need for surgery and the consequences of loss of thyroid function after surgery should be evaluated before surgery, and the pros and cons should be weighed and the patient’s confirmation should be obtained. There are two types of retrosternal goiter, one is complete retrosternal goiter and the other is goiter with inferior extension to the retrosternum. The former can be left untreated if there are no compression symptoms. If there are compression symptoms, surgical treatment should be considered, but if there is a “cold nodule”, it should be surgically removed, because once the adenoma or cyst bleeds or ruptures, it can cause tracheal compression and even sudden death. The principle of the latter treatment is the same as above. Ovarian goiter is characterized by normal thyroid imaging, and the clinic may have normal thyroid function or hyperthyroidism. Abdominal imaging can see ovarian teratoma, nuclear imaging can see abdominal ectopic thyroid image. The mechanism of occurrence of ovarian ectopic thyroid differs from that of neonatal ectopic thyroid.