How To Prepare continued...
Your doctor may ask you to eat a low-iodine diet for several days if this test is being done to check for thyroid cancer.
For a thyroid scan, you will either swallow a dose of radioactive iodine
or be given technetium in a vein (intravenously)
in your arm. When and how you take the radioactive tracer depends on which
tracer is used.
- Iodine can be taken as a capsule or a fluid 4 to 24
hours before the scan is done. Iodine has little or no taste.
- Technetium is
given 5 to 30 minutes before the scan is done.
Just before the test, you will remove your dentures (if you
wear them) and all jewelry or metal objects from around your neck and upper
You will be asked to sign a consent form that says you understand the risks of the test and agree to have it done.
Talk to your doctor about any concerns you have regarding the need for the
test, its risks, how it will be done, or what the results will mean. To help
you understand the importance of this test, fill out the
medical test information form(What is a PDF document?).
How It Is Done
A thyroid scan is done in the nuclear
medicine section of a hospital's radiology department by a person trained in
nuclear medicine (nuclear medicine technologist).
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 be given technetium in a vein (intravenously) in your arm 5 to 30 minutes before the scan.
For this test,
you will lie on your back with your head tipped backward and your neck
extended. It is important to lie still during this test. A special camera
(called a gamma scintillation camera) takes pictures of your thyroid gland from
three different angles. The test takes
about 30 minutes.
For a whole-body thyroid cancer scan, the camera will scan your body from head to toes.
thyroid scan, you can do your regular activities. But you will be asked to take
special precautions when you urinate. This is because your body gets rid of the
radioactive tracer through your urine. This takes about 24 hours. During this time, it is important to flush the toilet twice each time you use it and wash
your hands thoroughly after each time you urinate.
How It Feels
You may find it uncomfortable to lie
still with your head tipped backward.
There is always a slight chance of damage to
cells or tissue from radiation, including the low levels of radiation used for
this test. But the chance of damage from the radiation is usually very low
compared with the benefits of the test.
This test is not done for
pregnant women because of the chance of exposing the baby (fetus) to radiation. This test is also not recommended
for breast-feeding women or young children.