What happens during a scan?
Our animated video has been designed to help children learn about what happens during a scan.
Scans are used to give a detailed image of the brain. Your child may have a brain scan so that doctors can see whether a tumour is present and, if it is, its size and position. Scans are used for diagnosis and also for monitoring during and after treatment. The most commonly used scans are CT and MRI scans.
Neither scan is particularly better - it is more a question of which scan is best suited to meet the needs of the patient .
CT stands for Computerised Tomography. They are sometimes also called CAT scans.
CT scanners use x-rays to build up a 3D image of the inside of your child's head. It does this by taking many pictures of 2D 'slices' through their head. These slices are then stacked together, using a computer, to make a 3D image.
The CT scanner is shaped like a doughnut with a round hole in the middle - this is where your child's head will go.
MRI stands for Magnetic Resonance Imaging. This scan uses magnetic fields to build up a 3D image of the brain. It takes 'pictures' from several angles around your child's head to build a detailed picture. It can give many different kinds of information about the tumour and surrounding tissue.
An MRI scanner is an open-ended tunnel. The body part being scanned goes in the middle. For brain tumours, this usually means that your child's head and shoulders will be in the tunnel. If their spine is also being scanned, then their spine will be in the middle and their head may be near or out of the other (open) end.
Before your child's CT or MRI scan, it is important to let the doctors know if your child gets, or is likely to be very frightened of scans, has any allergies, is on any medications or has had a recent illness.
If your child has an adjustable shunt, this may need to be reset following an MRI scan, as the magnetic field can change the settings.
Keep a note of the settings of your child's shunt and check with the medical team that the correct levels have been reset after the scan. It is also good practice to put the settings on a medical alert bracelet, so medics can access them, if they ever need them and you are not there.
CT scans - although radiation is used, it is kept at a very low dose. They are used only when they are considered necessary, with the benefits outweighing the risks.
MRI scans - are completely safe. There are no risks associated with them, although they are not suitable for people who have metal in their body (for example, skull plates). Very rarely, the contrast medium can affect the kidneys - tell you child's medical team if your child has any kidney problems.
No, but if your child is given a contrast medium, this may make them feel hot or flushed or feel as if they have urinated (even though they haven't). These feelings usually last about a minute. Less commonly, some people have reported feeling cold after the contrast medium. Sometimes it can cause a metallic taste in the mouth, so it could be a good idea to bring mints or sweets with you to the appointment.
If your child was given the contrast medium via a 'cannula' (tube) in their hand or arm, this area may be a bit sore.
If your child feels claustrophobic, it is a good idea to let the hospital know before the day of the scan. They may refer your child to a play therapist, or they can arrange for your child to have a sedative to keep them calm.
With MRI scans, often a mirror can be placed so your child can see out of the scanner, making it feel less enclosed.
The radiography team will send a copy of the scan to your child's medical team in time for your next appointment, when you will be given the results.
How long this takes can vary - it can take some time for the very detailed images to be carefully analysed and discussed by your child's health team.
You should be given a time frame for your results by your child's doctor or clinical nurse specialist.
Page last reviewed: 02/2018
Next review due: 02/2021
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:
0808 800 0004 (free from landlines and mobiles)
Phone lines open Mon-Fri, 09:00-17:00
You can also join our active online community on Facebook - find out more about our groups.