What is a CT Scan?

A CT (computerised tomography) scanner is a special kind of x-ray machine. Instead of producing an image (radiograph) from a single direction, the x ray source is rotated around the patient - acquiring a cross-sectional image (tomogram) from many angles.
The x-rays from the beams are detected after they have passed through the body and their strength is measured. Beams that have passed through less dense tissue such as the lungs will be stronger, whereas beams that have been absorbed by denser tissue such as bone will be weaker. A computer can use this information to work out the relative density of the tissues examined. The computer processes the results, displaying them as a two-dimensional picture shown on a monitor.

How long does it take?

The examination varies depending on which area of the body is being scanned but can take anything from 15- 45 minutes.

What does it involve?

Please ensure that you have nothing to eat or drink for 6 hours before your appointment

You will be asked to change into a hospital gown. A member of radiology staff will explain the test to you and answer any questions you may have. The examination is carried out by a consultant radiologist (a doctor who specialises in X-ray procedures). A radiographer operates the equipment.

For abdominal CT you may be asked to drink a liquid to outline the bowel before commencing the examination.

You may require a small injection of contrast medium to assist the examination

The scanner looks like a large doughnut. During the scan the patient lies on a bed, with the body part under examination placed in the round tunnel or opening of the scanner. The bed then moves slowly backwards and forwards to allow the scanner to take pictures of the body, although it does not touch the patient. The length of the test depends on the number of pictures and the different angles taken.

What happens afterwards?

The results of the examination will be sent to the doctor who requested it. This can take up to 2 weeks. If you encounter any problems please contact your GP.

Are there any risks?

You will receive a dose of x-rays, however it is very unlikely to cause harmful effects. If you have an injection of contrast you may experience a sensation of warmth and a metallic taste in the mouth. Very occasionally transient side effects such as nausea or an itchy rash may occur, but other reactions are extremely rare.

If there is any chance that you may be pregnant you should inform us before the examination.