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.
How is the thyroid scan performed?
A thyroid scan is an outpatient procedure usually done in the nuclear medicine section of a hospital. This is usually part of the radiology department.
If you have a thyroid scan, you will be asked to take a drink, or swallow a pill containing the iodine. You will then wait for the iodine to be taken up by the thyroid - usually about 4 hours. At this time you lie under a scintography camera, and it will take pictures which correlate directly to the amount of iodine taken up by the thyroid. This is done by counting the intensity and location of the gamma rays emitted by the radioactively labeled iodine. You then leave the hospital, and return in 24 hours to have a second scan performed in the same manner.
There are no limitations during this 24 hour interval except that you will be asked to take precautions when you urinate. This is because the radioactive iodine is removed from your body by the urine, and it is safer to have others avoid contact with your urine during this time. Be sure to let the doctor performing the test know if you have an iodine allergy, or if you have ingested a lot of iodine-containing foods (like sushi) prior to the test.
There’s a small but safe amount of radiation contained in the radionuclide used in any thyroid scan. Your exposure to radiation will be minimal and within the acceptable ranges for diagnostic exams. There are no known long-term complications of having a nuclear medicine procedure.
Allergic reactions to the radionuclide material are extremely rare. The effects are mild when they occur. You may experience mild pain and redness at the injection site for a short time if you receive an injection of the radionuclide.
Even though the radiation exposure is minimal and short term, thyroid scans aren’t recommended for pregnant or breastfeeding women. Your doctor may recommend that you avoid becoming pregnant or fathering a child for six months after the test if you’ve had a metastatic scan.