MRI stands for magnetic resonance imaging. It creates pictures using magnetism and radio waves.
MRI scans produces pictures from angles all around the body.
You don't often have an MRI scan for ALL. But there might be certain situations were your doctor might want you to have one. For example if you have symptoms that suggest that you might have:
- leukaemia that has to spread to the
central nervous system (CNS)
- bleeding in the CNS
Symptoms might include headaches, feeing or being sick, seizures (fits), dizziness, unsteady when walking, changes to eyesight, weakness in your arms or legs and changes to your speech.
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 have 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. These include:
- 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
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 it.
Tell the department staff beforehand if you think you’re pregnant.
Eating, drinking and medicines
You might need to stop eating and drinking an hour or more before the scan. Talk to your doctor if this could be a problem, for example if you're diabetic.
You can usually take all your medicines as normal beforehand.
Some stick-on medicine patches contain metal and could overheat in the MRI scan, causing burns. Tell your radiographer beforehand if you use medicine patches. You might need to remove them before the scan.
What to expect
When you arrive at the scanning 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.
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.
Voiceover: This is an MRI scanner.
This type of scan uses magnetism to build up a picture of the inside of your body to help your doctor either make a diagnosis and decide what treatment you need or to find out if your treatment is working.
The radiographer makes sure you are lying in the correct position on the couch and explains what will happen.
You need to lie as still as possible.
MRI scans are very noisy so you wear ear plugs or headphones. During the scan you won’t feel anything.
The space you lie in can feel small, if you think you will find it difficult being in a small space, contact the scanning department before your appointment.
The radiographer controls the scan from a separate room but they will be able see and hear you throughout.
Here you can see an example of an MRI scan.
Once the scan is finished you can go home.
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 might stay in the department for about 15 minutes so the staff can make sure you’re okay. Your radiographer removes the cannula from the vein in your arm.
You can then go back to the ward if you are an inpatient or back home. You can eat and drink normally.
Getting your results
Ask your doctor when to expect your results and how you will receive them.
Waiting for test results can be a worrying time. You might have contact details for a specialist nurse and you can ask them for information. It may help to talk to a close friend or relative about how you feel.
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.
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.