Thyroid Scan (Scintigraphy)
What is a thyroid scan?
A thyroid scan produces an image of the thyroid gland after the intravenous injection of a weakly radioactive tracer.
The exam takes place in two steps.
First, the radioactive tracer is injected: either iodine-123, the more specific and therefore more frequently used tracer, or technetium-99m. The tracer is absorbed by the thyroid cells in varying degrees based on cell activity, thus allowing the radiologist to visualize “hot areas” where uptake is very high, and “cold areas” where uptake is low.
These areas are viewed through a gamma camera which records the concentration of the radioactive tracer in the different parts of the thyroid gland.
What is the purpose of a thyroid scan?
A thyroid scan is used to highlight morphological abnormalities such as a goiter or nodules, and/or functional abnormalities, such as hypersecretion.
The main diagnostic indications are:
- Nodules and multinodular goiters
In some instances of hyperthyroidism (Graves’ disease, pre-toxic or toxic hyperfunctioning nodule) or goiters, it is used to guide radioactive iodine-based treatment.
What happens during a thyroid scan at the American Hospital of Paris?
After completing the paperwork with our receptionist, you will be seen by a doctor from the department who will check the scan request, gather the main clinical, lab and ultrasound findings relating to your thyroid disorder, and explain what to expect during the thyroid scan.
A technologist will give you an intravenous injection of the radioactive product. There are no side effects and NO RISK OF IODINE ALLERGY.
The scan will be done two to three hours later (in the interim you will be allowed to leave the department).
The imaging itself takes ten to fifteen minutes. You will be lying down on a scanning bed with your neck extended.
Total exam time is three to four-and-a-half hours.
The results and images are given to you by the doctor, who will also send a report to your referring doctor the same day.
What are the risks of a thyroid scan?
The exam is painless.
- There are no particular risks: radiation exposure is very low and even young children can undergo the exam
- There is NO RISK OF IODINE ALLERGY: the injected dose is lower than your daily dietary intake
Thyroid scan: contraindications and precautions
- Injection of a radioactive tracer is contraindicated for pregnant women. If there is any possibility you might be pregnant, we recommend that you have your β-HCG level tested the day before the exam and bring us the result.
- You should discontinue breastfeeding for several days following the injection.
- If you have undergone a CT scan with an injection less than three weeks before the scheduled date of your thyroid scan, it is preferable to postpone your scan, except in the event of an emergency
How to prepare for a thyroid scan?
No special preparation is required and you do not have to fast prior to the exam.
Carefully gather the necessary documents: scan request from your doctor, blood test results, thyroid ultrasound, list of current medications, etc.