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Your child's MRI scan

This website page explains the benefits, risks and alternatives, as well as what you can expect when you come to hospital.

If you have any questions or concerns, please do not hesitate to speak to a doctor or nurse caring for your child.

What is a magnetic resonance imaging (MRI) scan?

An MRI scan uses a combination of a strong magnet and radio waves to produce detailed pictures of the inside of the body.

What are the benefits of an MRI scan?

An MRI scan can help to find out what is causing your child’s problem and help your doctor to find the best treatment.It provides much more detailed pictures of your child’s body than an ordinary X-ray.

It is particularly good at identifying problems in the spine, brain and in joints. It is also helpful for looking at other parts of the body, often when other types of scan have not given a full picture.

Unlike X-rays and computerised tomography (CT) scans, MRI scans do not use radiation.

Are there any risks?

Having an MRI is a very safe procedure for most patients, but patients with heart pacemakers and certain other surgical implants, for example a cochlear implant, can’t be scanned. You will be asked to complete and sign a safety questionnaire for your child before their scan to make sure it is safe for them to be scanned. You will also be asked to complete and sign a safety questionnaire for yourself to make sure it is safe for you to go into the MRI room with your child.

Your child may need to have an injection of contrast agent (dye) for their scan which can very rarely cause an allergic reaction. Please see the ‘Will my child need an injection?’ section later in this leaflet for more information.

Are there any alternatives?

If your child can’t have a scan, for example, if they have a cochlear implant, the radiologist (a doctor trained in studying scans and X-rays) may suggest an alternative type of imaging. This could be a CT scan or an ultrasound scan.

How can I prepare my child for the scan?

Your child can eat and drink as normal. If your child is taking any medication, please continue with this. If we do need your child to do anything in preparation we will send you information about this with your appointment letter.

Talk to your child

Preparing your child for the visit to hospital and the MRI scan will help them understand what is happening. From a young age, children are keen to talk about what they know about hospitals.

Talking to your child before their appointment will give them time to ask any questions or raise any concerns.

Will my child need an injection?

If we are scanning certain areas of your child’s body, we may need to give them an injection of contrast dye. This shows up on the scan and gives us more detailed pictures, particularly of your child’s blood vessels.

The injection will be given by inserting a small needle into a vein in your child’s arm.The contrast dye contains gadolinium, which may, occasionally, cause allergic reactions.

The most common allergic reactions can be headaches, nausea (feeling sick) and vomiting (being sick), sneezing, wheezing, runny nose, eye irritation, itching, hives, skin rash, swelling of the face, mouth, hands, feet or throat, difficulty in breathing, and low blood pressure. Before the scan we will check whether your child has had any previous allergies. If you would like more information about the injection, please ask the radiographer (a member of the radiology team who performs the MRI scan) before your child’s scan.

If your child has any problems with their liver and/or kidneys please raise this with the radiographer as extra tests may be required before administering any contrast.

What does your child need to wear?

Your child will need to change into a hospital gown. This is because some fabrics contain metallic elements which may heat up during the scan, and metal fastenings may spoil the pictures.

All jewellery and hair slides/clips must also be removed before the scan. If you are going into the MRI room with your child, you will need to take off your watch and take any credit cards or travel cards with magnetic strips out of your pockets.The scanner can affect these and stop them from working. Lockers are provided for your clothes and valuables.

What happens before the scan?

You will be given the opportunity to ask the radiographer any questions you have.Your child will also have the opportunity to spend a short time with a radiographer or a hospital play specialist (a member of staff trained to use play to prepare children for procedures) to discuss the scan. This will give your child a better understanding of what to expect during the MRI scan.

What happens during the scan?

In the scanner your child will be asked to lie on the scanner bed where they will be made as comfortable as possible as they will need to keep very still during the scan. It is important that they do not move, or the pictures could be blurred and the scan will have to be repeated. Once your child is positioned correctly, we will move them into the scanner – the part of your child’s body that we are scanning, must be in the centre of the machine. The scanner is a short tunnel.The radiographer will talk to your child during the scan to let them know what is happening and your child will be given a buzzer to press if they need to attract our attention during the scan.

When the scanner is working, it makes a loud banging noise. We will give you and your child headphones to wear, to reduce the noise. Your child can listen to music while they are being scanned, and for some scans they can watch a DVD – so please bring in your music or a DVD of your choice!

You can also bring a favourite teddy bear (which has no metal on it) to go into the scanner with your child.How long will the scan take?

This depends on which part of your child’s body is being scanned and the information that the doctor needs.

The radiographer will tell you how long they expect your child’s scan to take. Most scans take 20-30 minutes.

Will your child feel anything?

The scan should be completely painless. The most difficult part is keeping still. Please make sure your child is as comfortable and as relaxed as possible before we start.

Can you stay with your child during the scan?

Yes. Although this is a children’s hospital, you are still responsible for the behaviour of your child. If you are responsible for other children please arrange supervision for them so you can be with your child during the scan.

What happens afterwards?

As soon as the scan is finished you can go home, or back to the ward if your child is staying in the hospital. Your child can eat and drink as normal and resume their usual activities.The pictures taken during the scan are carefully studied by the radiologist who will produce a detailed report.

When will you get the results?

The results will be sent to the doctor who referred your child for the scan – usually a hospital specialist. If you make a clinic appointment for two weeks after the scan, the results should be available. For more urgent problems, they may be available sooner.

Further information

Find out more about having an awake MRI scan at the Evelina Children’s Hospital MRI unit.

GSTT ‘My MRI’ virtual reality app – Provides a virtual reality 3D experience of having an MRI scan at Guy’s and St Thomas’ Hospital MRI Unit. It is available to download from Google Play and Apple App Store.

Contact us

If you have any questions or concerns about your child’s MRI scan, please contact the MRI department on 020 7188 9218, Monday to Friday, 9am-5pm. Outside of these hours, please call 020 7188 46113932 and leave a message on our answer phone.


Leaflet number: 2314/VER5
Date published: November 2019
Review date: November 2022
© 2019 Guy’s and St Thomas’ NHS Foundation Trust
A list of sources is available on request

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If you have any questions or concerns about your child’s medicines, please speak to the staff caring for them or contact our helpline.

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