Thyroid scintigraphy is nuclear imaging of the thyroid gland in the neck. Also called a thyroid scan, this test can provide important information about the shape of the thyroid as well as the level of its function. A doctor may recommend it to a patient with a suspected thyroid abnormality, as part of a treatment follow-up, or in response to concerns about exposure to risks that might cause thyroid cancer. The test is minimally invasive, although it typically does require several hospital visits.
In this test, the patient swallows a small amount of a radioactive isotope in an iodine solution. Any thyroid tissue in the body will uptake the iodine along with the isotope. A gamma camera positioned over the patient can take photographs where the thyroid tissue will be highlighted because of the gamma emissions from the isotope. Typically patients need one set of images around four hours after taking the tracer material, and again approximately one day later.
Before a patient can have a thyroid scintigraphy test, the doctor will need to screen for certain risks. Pregnant and lactating patients cannot have this test, as there are concerns about the effects of the radioactive material on the developing fetus or baby. If thyroid screening is immediately necessary for such patients, doctors can discuss available options. It may be possible, for example, to pump and save milk ahead of time to use while the radioactive material works its way out of the body.
Certain medications, particularly thyroid drugs and some contrast materials that contain iodine, can interfere with thyroid scintigraphy. The patient may need to temporarily stop taking these medications before the test. Likewise, the doctor may recommend some temporary dietary changes to reduce the amount of iodine consumed in foods like iodized salt, seaweed, and seafood. These are usually necessary to get the clearest and most useful test results.
The amount of radioactive material needed for thyroid scintigraphy is very small. A nuclear medicine specialist can calculate the right dosage for a patient. It dissipates from the body rapidly and should not pose a risk to the health of the patient or people in the patient's vicinity. Patients with high radiation exposures from medications or other imaging studies may be an increased risk of complications, and should discuss this with their doctors.
Images from a thyroid scintigraphy can be reviewed for signs of abnormalities. The results may reveal masses in the thyroid as well as abnormal thyroid functioning. This information may be used to develop a treatment plan to manage the patient's thyroid condition.