A thyroid scan is a specialized imaging procedure for examining your thyroid, the gland that controls your metabolism. It’s located in the front part of your neck.
Typically, the scan works with nuclear medicine to evaluate the way your thyroid functions. Nuclear medicine involves using small amounts of radioactive material to diagnose disease.
Radioactive iodine is typically used in thyroid tests, including a thyroid scan. Your thyroid and most types of thyroid cancer absorb iodine naturally. The radioactive iodine builds up in your thyroid tissue. A gamma camera or scanner detects the radioactive emissions.
Your doctor will use the results of this test to evaluate how your thyroid is functioning.

Thyroid scans can help your doctor determine if your thyroid is working properly. You may also have a radioactive iodine uptake (RAIU) test with the scan to measure your thyroid’s reaction.
A radioactive material called a radioisotope, or radionuclide “tracer,” is given to you before the test. You may get it through an injection, a liquid, or a tablet. The tracer releases gamma rays when it’s in your body. A gamma camera or scanner can detect this type of energy from outside your body.
The camera scans your thyroid area. It tracks the tracer and measures how your thyroid processes it. The camera works with a computer to create images that detail the thyroid’s structure and function based on how it interacts with the tracer.
A thyroid scan can be used to evaluate abnormalities found in a physical exam or laboratory test. The images from this test can be used to diagnose:

• lumps, nodules (cysts), or other growths
• inflammation or swelling
• an overactive thyroid, or hyperthyroidism
• an underactive thyroid, or hypothyroidism
• goiter, which is an abnormal enlargement of the thyroid
• thyroid cancer

An RAIU evaluates the function of the thyroid gland. When your thyroid absorbs the radioactive iodine, it processes the iodine to make thyroid hormones. By measuring the amount of radioactive iodine in your thyroid gland, your doctor can evaluate the way you’re producing thyroid hormones.
A metastatic survey is a type of thyroid scan. It’s usually reserved for people with thyroid cancer. It can determine whether thyroid cancer has spread by detecting where the iodine is absorbed. The procedure is typically performed after thyroid surgery and ablation, or removal. It can identify pieces of the thyroid that remain after surgery.

• To determine thyroid gland functioning and identify any dysfunction of the gland.
• To help in the diagnosis of conditions like Hashimoto’s Disease, Grave’s Disease, thyroiditis, hypo or hyperthyroidism, etc.
• To identify goiter (enlarged thyroid), cysts, nodules, or other abnormal growths of the thyroid
• To assess thyroid nodules when the patient has hyperthyroidism.