A thyroid scan is used to gather information about the structure and function of the thyroid. The procedure uses a radioactive tracer and a special camera to measure how much of the tracer is absorbed from the bloodstream by the thyroid gland.
A thyroid scan can show the size, shape and location of the thyroid gland. The test can also locate spots in the thyroid gland that are overactive or underactive. The camera takes pictures of the thyroid gland from three different angles.
Thyroid scans are used to:
- Determine if the gland is working properly
- Diagnose problems, such as an overactive thyroid gland
- Assess the nature of a nodule discovered in the gland
- Detect areas of abnormality, such as lumps or inflammation
- Determine whether thyroid cancer has spread beyond the thyroid gland
- Evaluate changes in the gland following surgery, radiotherapy or chemotherapy
In performing a thyroid test, a radiotracer is usually administered 30 minutes before the test begins. The radioactivity of this tracer is very low, and there are no side effects. Actual scanning time for a thyroid test is 30 minutes or less.