Has your doctor told you to have a 'thyroid scan'? You might be a little scared when you hear the name. It's normal to feel scared when you hear words like 'radioactive'. But it's actually a very safe, commonly performed test. So today, let's talk about what this Thyroid Uptake and Scan is, why it's done, and how to prepare for it.
What is Thyroid Uptake and Scan?
Simply put, this is a special imaging test that checks the function of the thyroid gland in your neck. We call this a nuclear medicine imaging. Don't be scared by the name. It involves injecting a very small, safe radioactive substance (radiotracer) into your body and taking pictures of your thyroid gland with a special camera.
Imagine, a regular thyroid ultrasound can look at the shape and size of the gland. But with this Thyroid Uptake and Scan, you can get even more information, namely how the gland works . It's like looking at what's going on inside the engine of a car, rather than looking at the exterior.
'Uptake' and 'Scan' - what's the difference between the two?
These two are actually two processes, but they are usually done together. If you understand the difference between the two, your fear of the test will disappear.
| Test section | Simply put... |
|---|---|
| Thyroid Uptake | This measures how 'hungry' your thyroid gland is. That is, how much of the radioactive iodine given is 'eaten' (absorbed) by the gland. This can tell if the gland is overactive or underactive . No pictures are taken here, just a measurement. |
| Thyroid Scan | This is really a 'photo session'. Because the gland has absorbed the radioactive material, the shape and size of the gland, as well as which parts of the gland are working the most and which are working the least, can be seen in the pictures. It's like a 'working map' of the gland. |
Simply put, 'Uptake' measures the overall activity of the gland, while 'Scan' takes a picture of that activity spread throughout the gland.
Why do we have to do this test?
There are several reasons why a doctor might order this test. The main reasons are:
- Check if your thyroid gland is working properly: This scan can help determine the exact cause, especially if you have been diagnosed with hyperthyroidism.
- Find out more about thyroid nodules: After an ultrasound scan reveals a lump in the neck, it is important to know whether the lump is a 'hot' nodule that produces hormones, or a 'cold' nodule that does not produce hormones.
- See the results of treatment: This test is also done to see if there has been a change in the function of the gland after using medication for a thyroid disease or after surgery.
How should we prepare before the test?
There are a few things you need to be aware of and tell your doctor before this test. Following these instructions exactly is very important for the accuracy of the test.
- Very important: If you are pregnant, planning to become pregnant, or breastfeeding, you must tell your doctor and the person conducting the test before the test.
- Tell your doctor about all the medications you are taking: If you are taking any medications, especially thyroid medications, such as Methimazole or Propylthiouracil (PTU), your doctor will advise you how many days before the test you should stop taking those medications.
- Tell us about other medical conditions and allergies: Tell us about any other medical conditions you have and any allergies you have.
- Tell us about any recent scans you've had: If you've had anything like a CT scan recently, meaning within the last two months, that involves injecting iodine-containing contrast material, be sure to tell us about that as well. The iodine can interfere with this test.
- Fasting: You may be advised to refrain from eating or drinking for a few hours before the test.
If you have any questions about this, don't be afraid to ask your doctor. Follow their instructions exactly.
What happens during the test?
As we discussed earlier, 'Uptake' and 'Scan' are two processes. Let's see how to do these two separately.
How to do Thyroid Uptake
This is a very simple, painless process.
| Steps | What is happening? |
|---|---|
| Step 1 | You will be given a pill or liquid to drink that contains radioactive iodine (radiotracer). This has no taste whatsoever. |
| Step 2 | After drinking it, you can go home. You will be asked to come back to the hospital in 4 to 6 hours. |
| Step 3 | You will be made to lie on a bed, and a small device called a gamma probe will be placed around your neck to measure the amount of radiation absorbed by your thyroid gland. This will take less than 5 minutes. |
| Step 4 | Sometimes, you may be asked to come back after 24 hours and take this measurement. |
How to do a Thyroid Scan
This 'Scan' can be done after the 'Uptake' measurement or on a separate day.
| Steps | What is happening? |
|---|---|
| Step 1 | Most often, a radioactive substance (radiotracer) is injected into a vein in your arm. |
| Step 2 | After giving the substance a little time to be absorbed by the thyroid gland, you will be made to lie down on a bed. You will have to keep your neck tilted back a little. |
| Step 3 | A special camera is placed around your neck and takes pictures from different angles. It is very important to stay still during this time. |
| Step 4 | This entire process can take about 30 minutes. Sometimes, if you need clearer pictures, you may need to take a few more pictures. Don't worry about that, it's normal. |
What do you do after the test?
After the test, unless your doctor tells you otherwise, you can go about your normal activities. The most important thing is to drink plenty of water . Doing so will help flush out the very small amount of radioactive material in your body quickly through your urine.
Is there a risk in this?
The word 'radioactive' makes everyone feel scared. But in reality, the amount of radioactive material used in this test is very small. The amount of radiation your body is exposed to is very small.
Remember, the amount of radioactive material used in this test is very small, so the benefits of knowing your thyroid health accurately far outweigh this small risk.
However, as mentioned earlier, this radiation can affect a child in the womb of a pregnant mother or a child from a breastfeeding mother, so it is imperative to inform them about it.
Other possible, but very rare, complications include:
- There may be some slight pain where the medicine was injected. This will subside in a day or two.
- An allergic reaction to the radioactive material. This is very rare, but it is usually a mild allergic reaction.
When will I receive the report?
The images and measurements taken during the test are reviewed by a nuclear medicine specialist (radiologist) and a report is prepared. The report is sent to your doctor who ordered the test. Your doctor will then explain the details in the report to you.
Take-Home Message
- Thyroid Uptake and Scan is a very safe and useful test to learn about the function and health of your thyroid gland.
- Before having this test, be sure to tell your doctor if you are pregnant or breastfeeding.
- Inform your doctor about all medications you are taking and any recent CT scans you have had.
- It is very important to remain still during the test to get clear images.
- Drink plenty of water after the test.
- If you have any questions or concerns about this test, don't hesitate to talk to your doctor about it.
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