In the 1960s and 1980s, nuclear imaging (ECT) was once very “popular” in the examination of thyroid nodules, but since the 1980s, it has been replaced by more convenient and accurate tests. It is now well established that thyroid nuclear scans are not very meaningful in determining the benignity or malignancy of thyroid nodules. It is not necessary to perform a nuclear scan for thyroid nodules. The previous belief that a “cold nodule” is indicative of cancer is not correct, as 80% of the “cold nodules” are still benign. So, when should I get a nuclear scan? When the thyroid gland is not suspected to grow in the neck but in other parts of the body (ectopic thyroid), a nuclide scan can be done to clearly locate the nodule; another function is to clarify whether the nodule is functional or not; another meaningful part of the nuclide scan is to do whole-body imaging with iodine 131 after total thyroid cancer surgery to find metastases and prepare for high-dose iodine 131 treatment. However, a negative whole body image of iodine 131 does not mean that there is no metastasis of thyroid cancer; it is possible that the metastasis of thyroid cancer at this time is a metastasis that does not absorb iodine 131. Whether the result of nuclear scan is positive or not, it should be analyzed in combination with other imaging examinations, determination of serum thyroglobulin and calcitonin after total thyroidectomy, and fine needle aspiration. Positron emission tomography (PET-CT) is a new medical imaging technology developed in the last decade or so. However, because PET-CT is expensive, it is usually not used as a routine examination, but for postoperative follow-up of thyroid cancer without iodine 131 uptake, conventional iodine 131 whole body scan with negative imaging, poorly differentiated thyroid cancer or medullary carcinoma to detect recurrence and metastasis of thyroid cancer.