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Brain scans – CT scan, MRI scan

Brain scans provide a detailed 3D image of the brain by taking multiple pictures of the inside of your head. If you have a brain scan it will likely be a CT scan or an MRI scan, but there are other scans that you might have.

Scans are used during diagnosis or for monitoring your tumour. Some people will receive scans as part of active monitoring (also known as watch and wait). They allow doctors to see whether there is a tumour and, if there is, its size and position.

On this page we’ll look at the different types of brain scan and detail what you might expect before, during, and after a scan. We’ll cover:

What is a brain scan?

There are various types of scan that can produce a 3D image of the inside of your head, including your brain. 

The two types of brain scan that are most commonly used are:

CT scan

CT stands for Computerised Tomography. You may also sometimes hear doctors referring to CT scans as CAT scans – these are the same thing.

CT scanners use x-rays to take several cross-sectional pictures through your head, then use a computer to stack these 2D picture ‘slices’ into a 3D image.

MRI scan

Magnetic Resonance Imaging, or MRI, uses magnetic fields, rather than x-rays. MRI scanners take pictures from several angles around your head, then build these into a 3D image.

What other types of brain scan might I have?

There are some other types of scan that may be used to diagnose a brain tumour, or to find out more about a diagnosed tumour. These include:

  • PET (Positron Emission Tomography) scans
  • SPECT (Single Photon Emission Computerised Tomography) scans
  • fMRI (functional MRI scan)
  • specialised MRI scans.

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  • Find out as much information as possible about the process before having your scan, as this can help you if you’re worried about what’s going to happen
  • Find out the contact details of your medical team and make sure you know who to contact if you have any concerns
  • Take someone along to your appointment with you. It can be difficult to take in information during the appointment, so having someone else with you means that they might remember bits that you couldn’t at the time
  • Talk to your healthcare team about recording the conversation so you can refer back to it later
  • Make sure you let the medical team know if you’re feeling nervous, as they can find ways to help you feel more comfortable.

What to expect from a brain scan

Before your scan

You’ll need to take off anything metal, e.g. glasses, jewellery, hair clips, that may interfere with the scan. Fillings in your teeth and braces are fine, but tell your radiographer about them.

If you’re having an MRI scan, you’ll be asked if you have:

  • a pacemaker
  • any implants, such as a programmable shunt, infusion pump or skull section
  • ever worked in the steel or metal industries, as small metal fragments could be lodged in your body.

If you have, then an MRI may not be suitable for you, as it uses magnetic fields to take images. Your radiographer will be able to tell you more.

For both types of scan, you may be given a fluid called a contrast medium. Usually given via an injection (but sometimes as a drink), it helps to get a clearer image from the scan.

Depending on which contrast medium is used, it may make you feel warm all over, though some people feel cold. Or you may think that you’re passing urine, but you’re not.


For some people, the thought of having a scan can cause fear and anxiety – either about:

  • being in the scanner (I get claustrophobic. What’s it going to be like?)
  • waiting for the results (Has the tumour grown or returned?)

These feelings are often called ‘scanxiety’ (scan anxiety).

Find out more

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During the scan

The procedure for both CT scans and MRI scans is very similar.

You’ll lie, usually on your back, on the motorised flatbed that’s part of the scanner. The bed can move in and out of the scanner.

  • the CT scanner is shaped like a doughnut or ring, with a round hole in the middle– this is where your head will go
  • the MRI scanner is more cylindrical, like a short tube, and your head and shoulders will lie within it.

You’ll probably be given headphones, particularly for an MRI scan. You can usually take music to play through the headphones.

If you tend to get claustrophobic, it’s a good idea to contact the MRI or CT department before the day of your scan to find out the options and support available. You can also have a friend or relative with you if you’re nervous.  

Once the staff have got you in the right position, they’ll leave the room, but will be nearby. They can see, hear and talk to you, and you can hear and talk to them. They’ll tell you what will happen.

During the scan, you need to lie very still, so you shouldn’t talk while the actual scan is happening. You may be given a button to hold, which you can press if you need to stop the scan for any reason. But this will mean the scan has to start from the beginning again. 

You can breathe normally during the scan. 

The scan isn’t painful, nor will the scanner touch you. But, during the scan, you’ll hear noises from the scanner when it’s taking pictures:

  • for a CT scan, this will be soft humming and clicks
  • for an MRI scan, this will be very loud banging and clanging noises.
An image of a CT scan in a hopsital

What happens in a CT scan?

This video by Cancer Research UK shows what it’s like to have a CT scan

A patient in a MRI machine, with a member of the hospital team standing next to the machine.

What happens in an MRI scan?

This video by Cancer Research UK shows what it’s like to have an MRI scan

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After the scan

After the scan, you’ll usually be allowed to go straight home. You should arrange for a friend or relative to accompany you and take you home afterwards.

You should be told when you’ll get your test results. 

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Tips from our community

“I always keep my eyes tightly closed during scans. I ask for music and try to practise my yoga breathing. I usually come out feeling quite chilled.”

“One time in the scanner I began to panic. I pressed the panic button and the radiographer came into the room and sat with me, holding my hand for the rest of it. It helped me to feel calmer and less alone.”

“After MRI I always get a treat from my partner, or we go and do something nice together. It helps to make sure something positive happens that day and takes the focus off the scan.”

“Waiting for the MRI results is awful, so I recommend asking the radiographer when you can expect to get them. You can always call your Clinical Nurse Specialist if you are getting really anxious.”

By joining one of our Online Support Communities, you can get more tips about living with or beyond a brain tumour diagnosis from people who truly understand what you’re going through.

Find out more

Frequently asked questions

Neither scan is better than the other. It’s more a question of which scan is best suited to meet the needs of the person with a brain tumour.

MRI scans and CT scans are similar. Both build up detailed images of the brain. However, there are a few differences:

  • MRI scans don’t use ionising radiation to produce the images.
    (CT scans use x-rays [ionising radiation], while MRI scans use magnetic fields.
  • MRI scans usually give more detailed images than CT scans.
  • CT scans are quicker and quieter than MRI scans, and people tend to find them less claustrophobic.
  • CT scans can be used when there is an implant or piece of metal in the body that means an MRI is not suitable.

Your whole appointment will take quite a bit longer than the scan itself, as time will be spent getting you into the right position in the scanner.

For MRI scans, time will also be spent explaining the scan and going through the safety questionnaire with you.

For the scan itself:

  • CT scan – 5-10 minutes (though the newest CT scanners take about 1 minute to scan the whole brain)
  • MRI scan – 15-90 minutes (depending on the size of the area being scanned and how many images are taken).

How long this takes will vary.

Scan results should take 1-2 weeks, but it can help to ask how long you should expect to wait. Your doctors may need to first discuss your scan with other members of the medical team at their weekly Multi-Disciplinary Team (MDT) meeting.

Though CT scans use ionising radiation, it’s kept at a very low dose and they’re only used when they’re considered necessary, with the benefits outweighing the risks.

MRI scans are completely safe. There are no risks associated with them and they don’t expose your brain to ionising radiation. However, they aren’t suitable for some people who have metal in their body (e.g. some pacemakers).

Very rarely, the contrast medium can affect the kidneys, particularly if your kidneys aren’t working properly. So it’s important to tell you medical team if you have any kidney problems.

More information

Diagnostic scans for adults – PDF

Find out more about Diagnostic Scans in the full fact sheet.

Diagnostic scans for adults – Clear print PDF

Find out more about Diagnostic Scans in the full fact sheet – Clear print version, designed to RNIB guidelines.

If you have further questions, need to clarify any of the information on this page, or want to find out more about research and clinical trials, please contact our team:
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Coping with scanxiety

Learn more about how to cope when feeling anxious about upcoming scans or while waiting for results.