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MRI scan

Find out what an MRI scan is, how you have it and what happens afterwards.

What is it

An MRI scan creates pictures using magnetism and radio waves. It can help to find out where the cancer is and whether it has spread.

MRI stands for magnetic resonance imaging. It produces pictures from angles all around the body and shows up soft tissues very clearly. It can show up abnormal areas in the lymph nodes or other parts of the body.

Why you have it

You might have this test to look at your neck and chest to see if there are signs of thyroid cancer elsewhere in your body. MRI scans can pick up cancer that has spread into the soft tissues, such as in the neck.

If you have been diagnosed with medullary thyroid cancer, you might have an MRI scan of your tummy (abdomen) as well.

Preparing for your MRI scan

Before you go to your appointment, or when you arrive, you fill in a safety checklist. This asks about:

  • any operations you’ve had
  • whether you have any metal implants or other metals in your body

An MRI scan uses strong magnetism which could affect any metal in your body. This includes:

  • pacemakers or an implantable defibrillator (to treat abnormal heart rhythms)
  • surgical clips, pins or plates
  • cochlear implants (for deafness)
  • metal fragments anywhere in your body – for example from an injury, dental fillings and bridges. 

You can still have an MRI scan if you have some metals in your body, but your doctor and radiographer decide if it’s safe for you. Tell the scanner staff about any metals in your body.

Some people feel claustrophobic or closed in when they’re having an MRI scan. Contact the department before your test if you’re likely to feel like this. The hospital staff can take extra care to make sure you’re comfortable and that you understand what’s going on. Your doctor can give you medicine to help you relax if you need to.

An MRI is generally safe during pregnancy. But as a precaution, you usually won’t have one during the first 3 months of your pregnancy.

Tell the department staff beforehand if you think you’re pregnant. 

What to expect

When you arrive at the scan department

The radiographer might ask you to change into a hospital gown. You might not have to undress if your clothing doesn’t have any metal, such as zips or clips. 

You have to:

  • remove any jewellery, including body piercings and your watch
  • remove your hair clips
  • empty your pockets of coins and keys

It’s safe to take a relative or friend into the scanning room with you. But check with the department staff first. Your friend or relative will also need to remove any metal they have on them.

In the scanning room

Your radiographer takes you into the scanning room. The MRI machine is large and shaped like a doughnut.

MRI scan

You lie on your back on a couch that can slide into the MRI machine. 

You might have an injection of a dye (contrast medium) through a small plastic tube (cannula) into a vein in your arm. This helps to show up your body’s organs more clearly. Some people are allergic to the dye, so your radiographer will check first about any medical conditions or allergies you have.

After the dye injection you may:

  • feel sick
  • have a headache
  • feel warm or flushed
  • have a metallic taste in your mouth
  • feel a little dizzy

These effects are usually mild and last for a short time. Tell your radiographer if you feel unwell at any point during or after your scan.

Having the MRI scan

You need to lie as still as possible. The scan is painless but it can be uncomfortable to stay still. Tell them if you're getting stiff and need to move. 

Once you’re in the right position on the couch, your radiographer leaves the room. They can see you on a TV screen or through a window at all times from the control room. You can talk to each other through an intercom.

The couch moves through the MRI scanner. It takes pictures as you move through it. Your radiographer might ask you to hold your breath at times. 

The scanner makes a very loud clanging sound throughout the scan. You wear headphones to protect your hearing. You can also listen to music. Keeping your eyes closed can help.

This 1 minute video shows you what happens when you have an MRI scan.

After your scan

When the scan is over, your radiographer comes back into the room and lowers the couch so that you can get up.

You usually stay in the department for about 15 minutes after your scan if you've had the dye. This is in case it makes you feel unwell.  

Your radiographer removes the cannula from the vein in your arm before you leave.

You should then be able to go home or back to work, and also eat and drink normally.

Getting your results

You should get your results within 1 or 2 weeks. 

Waiting for results can make you anxious. Ask your doctor or nurse how long it will take to get them. Contact the doctor who arranged the test if you haven’t heard anything after a couple of weeks.

You might have contact details for a specialist nurse who you can contact for information if you need to. It may help to talk to a close friend or relative about how you feel.

For information and support, you can contact the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday.

Possible risks

An MRI is very safe and doesn’t use radiation. Some people can’t have an MRI but the checklist picks this up beforehand. Your doctor and radiographer make sure the benefits of having the test outweigh any possible risks. The risks include: 

Bruising and swelling

You might get a small bruise around the area where they put the needle in for the cannula. 

There's a risk that the contrast medium will leak outside the vein. This can cause swelling and pain in your arm but it’s rare. Tell your radiographer if you have any swelling or pain. Let your GP know if it doesn’t get better or starts to get worse when you’re at home.

Allergic reaction 

An allergic reaction to the contrast medium injection is rare. This most often starts with feeling weak, sweating and difficulty breathing. Tell your radiographer straight away if you feel unwell so they can give you medicine to control the reaction.

Last reviewed: 
03 May 2018
  • The Royal Marsden Manual of Clinical Nursing Procedures, 9th, Professional Edition

    L Dougherty and S Lister (Editors)

    Royal Marsden Manual Series, Wiley-Blackwell, 2015

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