What is a Thyroid Scan?
A thyroid scan is an imaging test that helps your doctor see how your thyroid gland is functioning. The thyroid is a butterfly-shaped gland in your neck that produces hormones important for regulating your metabolism and many other body functions.
How Does a Thyroid Scan Work?
The scan uses a small amount of radioactive material (Technetium-99m pertechnetate) that mimics iodine, which is naturally used by your thyroid gland to produce thyroid hormones. This radioactive tracer allows us to:
- See the size, shape, and position of your thyroid gland
- Measure how your thyroid is functioning, that is, is it overactive, functionally normally, or underactive
- Identify areas of abnormal thyroid tissue
Why Might I Need a Thyroid Scan?
Your doctor may recommend a thyroid scan to:
- Evaluate an overactive thyroid gland (hyperthyroidism)
- Investigate the cause of an enlarged thyroid gland
- Check for thyroid nodules
- Determine appropriate dosing for radioactive iodine treatment
What Can I Expect During the Procedure?
- A small amount of radioactive tracer will be injected into a vein in your arm.
- You’ll wait approximately 20 minutes while the tracer concentrates in your thyroid gland.
- You’ll lie on an examination table with your neck slightly extended.
- A special camera (gamma camera) will take images of your thyroid from different angles.
- The entire procedure typically takes 30-45 minutes.
What Do the Results Mean?
- Uniform uptake: Normal thyroid tissue absorbs the tracer evenly
- Hot areas: Regions with increased tracer uptake may indicate overactive thyroid tissue
- Cold areas: Regions with decreased tracer uptake may indicate abnormal thyroid tissue that requires further evaluation
If cold areas are detected, your doctor may recommend:
- A second scan using a different tracer (99mTc-Sestamibi)
- An ultrasound examination
Preparation for Your Thyroid Scan
- Inform your doctor about all medications you’re taking – please share a full list of your medication with the technician performing your scan
- You may need to stop certain medications influence thyroid function or contain iodine (for example, neomercazole, carbimazole, amiodarone)
- You might need to fast for a few hours before the test
- Remove jewelry or metal objects from the neck area
- Tell your doctor if you are pregnant or breastfeeding
After the Procedure
- You can resume normal activities immediately
- Drink plenty of fluids to help flush the radioactive material from your body
- The small amount of radiation used in the test is generally considered safe and will naturally leave your body within a day
Your doctor will discuss the results with you during your follow-up appointment.
