A CT scan uses x-rays to build a three-dimensional (3D) picture of the inside of the body. You may be given either a drink or injection of dye.

What is a CT scan?

A CT scan makes a three-dimensional (3D) picture of the inside of the body. The 3D picture is built up using lots of detailed x-rays taken by the CT scanner. It uses a small amount of radiation. This is very unlikely to harm you. It will not harm anyone you come into contact with.

Before a CT scan

You will get an appointment letter telling you if you need to do anything before the scan. You may be asked not to eat or drink for a few hours before the scan. This depends on the part of the body being scanned. If this is a problem for you, call the number on your appointment letter.

When you arrive at the hospital, you may be asked to put on a hospital gown. The staff may also ask you to remove any jewellery or objects containing metal, including:

  • piercings
  • hair clips
  • zips
  • your bra.

This is because the metal in these objects can affect the picture made by the scanner.

You may have a drink or injection of a dye. This is called a contrast. It helps show certain areas of the body more clearly. The contrast may make you feel hot all over for a few minutes. It is important to let your doctor know if you are allergic to iodine or have asthma. This is because you could have a more serious reaction to the injection.

Having a CT scan

You have the scan in the x-ray department at the hospital. The person who works the scanner is called a radiographer. The scan takes 5 to 10 minutes, but you may be in the department for longer. You lie very still on a narrow bed. The bed moves slowly back and forward through the donut-shaped scanner.

You will probably be able to go home as soon as the scan is over. The radiographer may suggest you drink plenty of water for the rest of the day. This will help flush out the contrast.

Types of CT scan

There are some specialised types of CT scan. These may be used to help diagnose some types of cancer. They may also be used to check how well treatment is working.

  • CT urogram

    A CT urogram looks in more detail at the bladder, kidneys and ureters (tubes that drain urine from kidney to bladder).

  • Virtual colonoscopy (CT colonography)

    A virtual colonoscopy looks at the bowel in more detail.