Thyroid scan

A thyroid scan uses a radioactive tracer and a special camera. The tracer can be swallowed or can be injected into a vein. It travels through your body, giving off radiation signals. The camera “sees” the signals and can measure how much tracer the thyroid absorbs from the blood.

A thyroid scan is done to:

• Help find problems with the thyroid gland.
• Check a thyroid nodule.
• See whether thyroid cancer has spread outside the thyroid gland. A whole-body thyroid scan will usually be done for this evaluation.

• The tracer used in this test is either radioactive iodine or technetium. You will either swallow a dose of iodine 4 to 24 hours before the scan. Or you may be given technetium in a vein (intravenously) in your arm 15 to 30 minutes before the scan.
• For the scan, you will lie on your back with your head tipped backward and your neck extended.
• A special camera takes pictures of your thyroid gland from three different angles.
• For a whole body thyroid cancer scan, the camera will scan your body from head to toes.

You may need to stop eating for several hours before the test. If the test is being done to check for thyroid cancer, you may have to eat a low-iodine diet for several days before the test. Your doctor may have you stop taking thyroid medicines for some time before this test.

If you are breastfeeding, you may want to pump enough breast milk before the test to get through 1 to 2 days of feeding. The radioactive tracer used in this test can get into your breast milk and is not good for the baby.

A whole-body scan will show whether iodine is in bone or other tissue (iodine uptake) after the thyroid gland has been removed for cancer. The whole-body scan can check to see if cancer has spread to other areas of the body.