A CT scan takes a series of x-rays (“slices”) to build up a three-dimensional picture of structures inside the body.
CT stands for Computed Tomography. The scan is sometimes called “CAT”, which means Computed Axial Tomography.
CT is not recommended for routine imaging in children or adults with a known or suspected constitutional RB1 mutation. Radiation exposure increases second cancer risk in these individuals.
CT may be used:
to aid diagnosis and staging of retinoblastoma
for radiotherapy setup
in emergencies when a rapid view of the brain is important
in routine follow up of high risk retinoblastoma when MRI is unavailable
Before the Scan
Some children feel claustrophobic inside the scanner, so prepare your child for this beforehand. You can often arrange a pre-scan visit with your child to familiarize yourselves with the machine.
Your child may be asked to remove clothing or jewellery, and put on a hospital gown.
Before or during the scan, your child may be given an intravenous injection of liquid contrast dye that creates clearer pictures of certain tissue types. The contrast may make your child feel warm and tingly all over for a few minutes. This does not hurt, but she may cry if she is unprepared for the sensation.
The contrast often contains iodine. The technician will first ask if your child is allergic to it or has asthma. If the department knows about this in advance, the contrast can usually still be given, but your child will be given a steroid the day before and on the day of the scan, to prevent a reaction.
During the Scan
This painless scan takes 10–30 minutes. Your child lies on the scan bed, with her head on a special pillow. The bed then moves so your child’s head is inside the scanner. During the scan, she will be able to hear, and speak to, the technician through a microphone inside the scanner.
The technician leaves the room during the scan. Many hospitals allow parents to stay if the scan is done awake. You have the right to request this. Do advocate to stay with your child as your presence can be very reassuring. You will be asked to wear a lead apron to protect you from radiation exposure.
You will be asked to wait in the department until the technician has reviewed all images to ensure they are sufficient.
Young children are often given a short acting general anaesthetic as it is vital they lay very still during the scan to obtain good images. However, with good child life support, children as young as 2 can complete the scan awake.
After the Scan
If your child completes the scan awake, you will be free to go as soon as it is over. If she has a general anaesthetic, you will usually be taken to recovery or a day care ward. You will be allowed to leave once she is fully awake and has had something to drink.