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Starship Paediatric Radiology

Public Service, Radiology, Paediatrics

Computed Tomography (CT)

The CT scanner that we use was donated by the Starship Foundation with special help from Lucy Lawless.

C- or C+ may be written on the requisition.
C-  means no intravenous contrast is given for the CT examination.
C+ means that contrast - a clear fluid that contains iodine which is visible on the images - is given through a needle or small tube (catheter) that has been placed in a vein before the images are acquired.
Often, for abdominal scanning, and before coming to the CT room, the child is given fluid to drink that contains iodine or a small amount of barium. This oral contrast fills the inside of loops of bowel, and allows us to identify where they are in the abdomen.

For the CT examination, the child usually lies on his or her back on a special x-ray table. We make sure that there is no metal on the child, or in a pocket because it causes artifacts (unwanted effects on the image). The table moves through a large donut-shaped structure which is a sophisticated x-ray machine combined with a special computer. The images are called “scans” and sometimes, “CT cuts” but this refers to cross-sectional images that are obtained after the computer has analysed the data; the machine does not touch or cut the child. The radiographer puts the child into the correct position, on the examination table, for the area that is to be imaged.
The first scan that is obtained is of the area of interest, for example the brain, or abdomen or chest, and this is used as a type of map so that the cross sections are taken of the appropriate structures.  Sometimes, if the blood vessels need to be visible, or if the amount of blood flow to a structure needs to be shown, intravenous contrast is administered, usually through a vein in the arm or hand. This intravenous contrast looks like a clear liquid but it contains iodine which is visible on x-ray images. Depending on the child’s medical or surgical problem, we sometimes need a second set of scans as the contrast moves through the bloodstream and into the kidneys where it is excreted into urine.

The child may have to hold his or her breath for some examinations; they should lie as still as possible. If the child is very little and we need to have the child very still, we may need to give the child medicine for sedation. In some cases, we work with the anaesthetists who can give a child general anaesthesia.
Usually a parent or caregiver, who is given a lead apron to wear, can be in the CT room with the child. The technologist sits in a separate control room that has a glass window between it and the scanner. There is an intercom so that people can talk between the two rooms.
The scan time will vary depending on the type of examination required, but as a rule it will take less than 30 minutes.

The list below provides  instructions appropriate to the child’s age and type of scan.  The instructions are general.  You will be given detailed instructions at the time you receive your appointment.  If you do not think your child can keep still for their CT, or if there is any other problem, please let the booking co-ordinator know well before the scan date so we can make other arrangements.

  • Babies under 3 months of age: keep awake and do not feed for 3 hours before the appointment. Bring a bottle feed, security toy & pacifier if the child uses one. With these measures babies often sleep through their scan.
  • Children 3 months to 3 years or less than 20kg in weight: most children in this age group will need sedation (a medicine given by mouth to make them sleepy). This will be given in the Radiology Department. In case the child needs sedation, the child of 3 months to 3 years of age must fast (have no food or milk) for 4 hours before the scan. They can have water or clear fluids such as diluted Ribena, apple juice, up to 2 hours before the scan.  Clear fluids are anything you can see through.  Do not give fizzy drink or milk. 
  • Children over 3 years of age or more than 20kg in weight: with our new ultrafast scanner most of these children do not need any sedation.
    If they are having intravenous contrast, they must not have any food or drink for 4 hours before the scan.  This instruction does not include the oral contrast that might be needed. Instructions for that are below.



If sedation fails, or if an older child cannot keep still, your child may need a brief GA for the CT.  This is performed by qualified paediatric anaesthetists in the CT room. Fasting times vary for a child having a general anaesthetic, depending on their age and medical condition. Specific instructions will be sent to the parent/caregiver with the appointment. Please follow them correctly. If you have any questions please phone the booking clerk well in advance. The booking clerk’s number will be on the appointment letter.


For scans that require abdominal contrast, a packet of E-Z-CAT dry barium sulfate suspension will be given or sent to the parent/caregiver.

Instructions: please read and follow the instructions below, NOT those on the E-Z Packet.

Inside this envelope is a pack of E-Z-CAT DRY BARIUM SULPHATE SUSPENSION.

  1. Pour 900mls of water into a container.
  2. Pour contents of packet into the container and stir well.
  3. Let mixture stand for 5 minutes and stir again.
  4. Stir again before drinking. 

You may prepare the mixture ahead of time and store in the refrigerator. There will be excess fluid that can be discarded.

60mls 4 hours prior to CT Scan
60mls 2 hours prior to CT Scan
Nothing else to eat or drink in the 4 hours prior to scan.

100mls at 4 hours prior to CT Scan
100mls at 2 hours prior to CT Scan
Nothing else to eat or drink in the 4 hours prior to scan.

200mls at 4 hours prior to CT Scan
200mls at 2 hours prior to CT Scan
Nothing else to eat or drink in the 4 hours prior to CT Scan.

250mls at 4 hours prior to CT Scan
250mls at 2 hours prior to CT Scan
Nothing else to eat or drink in the 4 hours prior to CT Scan.

400mls at 4 hours prior to CT Scan
400mls at 2 hours prior to CT Scan
Nothing else to eat or drink in the 4 hours prior to CT Scan.

Your child may be given another small drink of the same contrast when you arrive for the scan.

This page was last updated at 11:51AM on April 14, 2021.