About a thyroid MRI scan
The thyroid is a small, butterfly-shaped gland at the front of the neck, just below the Adam’s apple, wrapped around the windpipe. It makes hormones that control how fast the body uses energy. A thyroid MRI uses a strong magnetic field and radio waves, not X-rays, to show the thyroid and the structures around it, including the windpipe, gullet, blood vessels and lymph nodes.
An ultrasound scan, along with blood tests, is the first test for most thyroid problems, including lumps (nodules) and swelling. It shows the thyroid in fine detail and can be used to guide a needle biopsy. MRI is not used to check thyroid function or to tell whether a nodule is cancer. It is used when more information is needed about how far something extends, for example:
- a large goitre (swollen thyroid), to see whether it reaches down behind the breastbone (retrosternal goitre) and whether it is pressing on the windpipe or gullet
- a thyroid cancer, to see whether it has spread into nearby tissues or lymph nodes before surgery
- to check the neck after treatment
CT is often used for these questions too. MRI does not use radiation or the iodine-based contrast dye used in CT, which can be helpful if you may need radioactive iodine treatment, as iodine contrast can delay it. For other lumps in the neck, see neck (soft tissue) MRI.
What happens during the scan
You lie on your back on the scanner bed with a coil placed around your neck. The scanner is loud, so you will wear ear plugs or headphones, and the radiographer can talk to you throughout. You need to keep still and try not to swallow or cough while each set of pictures is being taken; the radiographer will tell you when you can. An injection of contrast dye (gadolinium) may be used; where contrast is needed, it is charged separately.
What the scan can show
A thyroid MRI can help to look at:
- the size of a large goitre
- goitre extending behind the breastbone (retrosternal goitre)
- pressure on the windpipe, gullet or blood vessels
- spread of thyroid cancer into nearby tissues
- enlarged lymph nodes in the neck
- the neck after thyroid surgery or treatment
When to get urgent help: call 999 or go to A&E if you have a swelling in your neck with difficulty breathing or noisy breathing. See a GP urgently if you have a lump in your neck that is getting bigger, a hoarse voice for more than 3 weeks, or difficulty swallowing.
Preparing for your scan
No special preparation is needed, and you can eat and drink normally. Upload any previous ultrasound, biopsy and thyroid blood test results when you book. If you are due to have radioactive iodine treatment, tell your specialist and the scanning centre.
You can usually eat, drink and take your normal medicines unless the scanning centre tells you otherwise. Wear loose, comfortable clothing without metal zips or buttons, and leave jewellery at home. You will be asked to remove metal items such as hair clips, hearing aids, coins and keys, and you may be asked to change into a gown.
Before the scan you will complete a safety questionnaire. Tell the team if you have a pacemaker, any metal implant, surgical clips or other device, if you have kidney problems or allergies, or if you are, or might be, pregnant or breastfeeding. If you feel anxious in enclosed spaces, let us know when you book. Some centres can offer a relaxant, and if you take one you will need someone to take you home and must not drive for 24 hours.
Frequently asked questions
Can an MRI tell if a thyroid nodule is cancer?
No. Thyroid nodules are assessed with ultrasound and, if needed, a needle biopsy. MRI is mainly used to see how far a goitre or cancer extends.
Is MRI or CT better for a goitre?
Both can show how far a goitre extends and whether it is pressing on the windpipe. CT is often used first. MRI avoids radiation and iodine-based contrast. Your specialist will say which is needed; if you are unsure, contact us before booking.
Will I need to stop my thyroid medicine?
No. You can take your usual medicines, including thyroid tablets, as normal before the scan unless your specialist tells you otherwise.
Do I need a referral?
You can tell us if you have a referral from your GP, physiotherapist or consultant and upload it when you book. If you do not have one, select “no referral” when you book and the scanning centre will confirm the next steps with you.
Sources
- NHS – Goitre
- NHS – Thyroid cancer: diagnosis
- NICE NG230 – Thyroid cancer: assessment and management
- Retro-sternal Goitre: an Overview (PMC)
- NHS – MRI scan
The information on this page has been gathered from various sources and is provided for general information only. It is not medical advice. TOP MRI is not liable for the accuracy or completeness of this information. Please speak to your doctor or the scanning centre about your own situation.