Thyroid Scan
Medical Author: Ruchi Mathur, MD
Medical Editor: Melissa Conrad Stoppler, MD
What is the thyroid gland?
The thyroid is a gland that makes and stores essential
hormones that help
regulate the heart rate, blood pressure, body
temperature, and the rate of chemical reactions (metabolism) in the body. It is
located in the anterior neck
just below the Adams apple.
The thyroid gland is the, is the main part of the
body that takes up iodine. In a thyroid scan, iodine is labeled with a
radioactive tracer, and a special camera is used to measure how much tracer is
absorbed from the bloodstream by the thyroid gland. If a patient is allergic to
iodine, technetium can be used as an alternative.
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 a iodine allergy, or if you have
ingested a lot of iodine-containing foods (like sushi) prior to the test.
Next: When is thyroid scanning helpful? »
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