CT scan factsheet


Computerised tomography (CT) scans are used to see the inside of the body in detail.

They are used to look at:

  • bones
  • organs
  • muscles
  • blood vessels.

 Before the scan

You will get instructions from the hospital or your child’s doctor before the CT scan. 

Let your child’s treatment team know if they have:

  • any allergies
  • asthma
  • kidney problems.

Parents and carers are encouraged to stay and support their child during the scan. If a parent or carer is pregnant, they will not be able to stay in the scan room due to the radiation.

Instructions may be different depending on what part of your child’s body is being looked at.


Some children might need to fast nil by mouth before a CT scan if they are:

  • having a general anaesthetic – medicine that puts your child to sleep so they don’t feel stress or pain
  • being sedated – medicine that relaxes your child but is not as intense as a general anaesthetic.

Fasting nil by mouth means no eating or drinking before the scan. This lowers the risk of aspiration. 

Aspiration is when food or water is brought up into the lungs during a procedure. Aspiration can be life-threatening.


Contrast is a liquid that travels through the body and helps different parts show up clearly on the scan.

Contrast can be given:

  • oral contrast – a drink
  • contrast dye – an injection into the bloodstream.

Contrast can make your child feel nauseous, so they may be asked to fast nil by mouth before the scan. 

Some children have a serious allergic reaction to contrast dye called anaphylaxis. 

Let your child’s doctor know if they have any allergies or have had a reaction to contrast dye before.

 During the scan

A CT scan is done in a big X-ray machine, shaped like a doughnut. Your child will be exposed to some X-ray radiation during the scan.

The machine will make a soft noise like a fan. It will also make some clicking noises as the pictures are taken. 

The scan will go for a few minutes and should not be painful. 

Your child will need to stay very still for the scan, and they may be asked to hold their breath for a few seconds at different times.

Speak to your child's doctor if you have any questions or concerns about the CT scan.

 After the scan

Your child should be able to go home after the scan.

Children who had contrast dye will need to wait 15 minutes after their scan to make sure they do not have an allergic reaction.

Last updated Tuesday 7th May 2024


This factsheet is provided for general information only. It does not constitute health advice and should not be used to diagnose or treat any health condition.

Please consult with your doctor or other health professional to make sure this information is right for you and/or your child.

The Sydney Children’s Hospitals Network does not accept responsibility for inaccuracies or omissions, the interpretation of the information, or for success or appropriateness of any treatment described in the factsheet.

© Sydney Children’s Hospitals Network 2024