CT scan

What is a CT scan?

A CT scan is a sophisticated X-ray that takes cross-sectional and 3-dimensional pictures of any part of the body using a computer.

Why is this test done?

There are several reasons why a CT scan is performed. One of the main reasons is to help the doctor make an accurate diagnosis, particularly when normal X-rays have not detected a disease. CT scans can often replace other techniques used to diagnose, such as exploratory surgery. Some people will have a CT scan to determine how well they have responded to a particular treatment, for example, after chemotherapy.

What do I need to do to prepare for this test?


Generally no preparation is needed before a CT scan. A small number of people find that having a CT scan makes them feel very claustrophobic, especially those having a scan of the head. If you have problems in confined spaces you may wish to discuss this with your doctor before you go. A light sedative can be given. Let your doctor know if you have any allergies.

You may be asked to drink a contrast medium (a type of dye) and to not eat or drink for a few hours prior to having an abdominal scan. This allows the radiologist to get a better picture of your bowel.

Children and infants

Generally, children and infants are given a light, general anaesthetic or sedative. This is to ensure that they lie still during the test, which can take up to an hour. If your child requires an anaesthetic you will need to make sure he or she does not eat or drink anything for 6 hours before the test. You will also be given the opportunity to speak to an anaesthetist and will be required to sign a consent form. Children who have had sedation or an anaesthetic can usually go home one or 2 hours after the test, if all has gone well.

What happens during the test?

A radiographer (a specialist in taking X-rays) or a specialist nurse will meet you. You will be asked to change into a hospital gown and lie on the scanner table.

The table can move up in the air and then slide so that any part of you can be placed inside a short, circular tunnel measuring about 30 centimetres in length and 60 centimetres across. You will be in the CT room by yourself during the test, but you can speak to the radiographer at any time through an intercom.

During the test you will be asked to keep very still. The radiographer will ask you to hold your breath while the picture is taken. A number of pictures will be taken and the table will be moved slightly each time. For chest and abdominal scans, you will be asked to hold and release your breath many times.

If you are having a scan of your abdomen, you may be given a few glasses of a bitter tasting drink 30 minutes before the test. If the scan is of the lower abdomen, a limited enema may be given before the pictures are taken. These help to improve the contrast in the pictures. Women may be asked to insert a tampon to outline the vagina.

What are the risks?

This is a very safe test. The only complication that may occur is an allergic reaction to the dye injection. If an allergic reaction does occur, it will be treated immediately with medicine. Some medical conditions affect the way your body gets rid of the dye, so read the consent form carefully.

If you are pregnant and a CT scan has been advised, make sure your doctor knows that you are pregnant. You and your doctor can then decide whether you should have a scan.

What happens after the test?

You can resume normal physical activity and return to work as soon as the test is done. If the test took a long time, you may be watched for signs of light-headedness or fainting when you first sit or stand up.

When the test is finished, a radiologist will study the pictures. The results and a written report will then be sent to the doctor who organised the test. A follow-up appointment will be made to discuss them with you.

Further information and support

Talk to your doctor. Contact the hospital or radiology centre where you are having the CT scan.

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