A thyroid scan (or thyroid uptake scan) is a type of nuclear medicine scan which relies on an injection of a low dose of radioactive Technetium99m. This radioactive isotope is harmless to patients, but is extracted from the blood by the thyroid gland in exactly the same way as Iodine. The Technetium emits gamma rays which can be detected by a gamma camera and produces a picture of the uptake within the thyroid gland. The advantage of this technique is that it is possible to quantify the uptake of tracer within the thyroid gland to give an indication of the activity.
Uses for the thyroid scan include:
- Evaluation of the activity and/or location of the thyroid gland in neonatal hypothyroidism
- Evaluation of causes for thyrotoxicosis
- Evaluation of thyroid nodules
- Evaluation of suspected ectopic thyroid tissue
It is important to know if patients have had any tests, such as an x-ray or CT scan, surgeries or treatments using iodinated contrast material within the last two months or if they are taking medications or ingesting other substances that contain iodine, including kelp, seaweed, cough syrups, multivitamins or heart medications. These can interfere with thyroid uptake and the scan.
At Trinity Medical Imaging, the thyroid scan can be combined with SPECT-CT for accurate location of ectopic thyroid tissue and retrosternal extension of thyroid goitres.
Thyroid scan preparation
What is a thyroid uptake scan?
A thyroid uptake scan uses small amounts of a radiopharmaceutical which is injected into a vein and accumulates in the thyroid gland (which lies in the midline of the front of the neck). The gamma camera detects the gamma rays coming from the radiopharmaceutical and creates an image with information about your thyroid’s size, shape, position and function This can highlight information which helps the doctor to diagnose your condition.
Are there are any risks?
As the gamma rays are similar to X-rays, there are small risks associated with being exposed to radiation. However, the radiation decays away over a few hours and the amount of radiation used in medical imaging is very low. This is comparable to the natural radiation we all receive from the environment over about 2 months. If you are concerned about the risks of the radiation, please speak to a member of our team.
Are you required to make any special preparations?
When making your appointment, you will be asked what medication you are currently taking, and you may need to stop certain drugs before your scan. In some cases this can be up to 3 months before your scan. You will be asked if you have taken any food (e.g. kelp) which contains iodine. You should tell us if you have had a radiology scan involving a contrast injection within the last 2 months. After your injection, you should use the special toilet for nuclear medicine patients.Your technologist will show you where the toilet in the department is.
Can I eat and drink normally?
Large meals can slow the absorption of the radiopharmaceutical, so we ask you to avoid meals for at least 2 hours before and 2 hours after the injection. You can drink normally.
If you are pregnant or breastfeeding
If you are pregnant, or think you may be pregnant, you mustinform the department before attending, and certainly before the radiopharmaceutical is administered.
If you are breastfeeding, please inform the department before attending and you will be advised as to whether you will need to take any precautions. You may be advised to avoid breastfeeding for a few hours afterwards and you may need to express milk before your scan.
Can you bring a relative/friend?
Yes you can, but for reasons of safety, they may not be able to accompany you into the examination room, except in very special circumstances. Please do not bring children with you as they will potentially be exposed to radiation from other patients.
Arriving for your appointment
When you arrive for your appointment, please go to the reception desk, after which you will be shown where to wait until collected by a technologist.
The technologist will explain the procedure, and you can ask any questions. You may be asked some questions about your health, or whether you have had this examination before.
The technologist will then give you the injection of radiopharmaceutical preparation into a vein in the arm. This is just like having blood taken.
What happens during the scan?
You do not need to undress but please remove any jewellery or metallic objects from around your neck. You will be taken to the scanner room and made comfortable either lying down on the couch or sitting on a stool in front of the gamma camera. The technologist will position the gamma camera over the front of your neck and you will be asked to remain still. You can breathe normally throughout.
The technologist will remain in the control room and watch you through the glass screen in the examination room. It may be necessary to take one or two more localised views, if more detail is required.
Will it be uncomfortable?
No. Apart from the injection, you will not feel anything.
Can I listen to music while I have my scan?
Your technologist will ask you whether you would like to listen to music during your scan. You may bring in a CD or select music from our selection.
How long will it take?
The scanning process usually takes about 20 minutes, and your total time in the department will usually be less than one hour.
Are there any side-effects?
No, the injection causes no side-effects, nor will you feel drowsy. You can drive home afterwards and go about your normal activities.
In addition to mothers who are breastfeeding, parents with young children should notify the technologist, who will explain that it is advisable not to have prolonged close contact with them for the rest of the day. This is to avoid their being exposed to unnecessary radiation.
When will you get the results?
The scan will be examined after your visit and a written report on the findings will be sent to your referring doctor within 7 days.
The radiopharmaceutical required for this examination is ordered especially for you. If you cannot attend your appointment, please let the department know as soon as possible, so that we can use it for someone else.
We hope that this leaflet has answered your questions, but remember that this is only a starting point for discussion about your treatment with the doctors looking after you. Make sure you are satisfied that you have received enough information about the procedure.