Computed Tomography (CT) is a sensitive diagnostic tool that uses X-rays to take a series of two-dimensional cross-sectional images ('slices') around an axis. It has been in widespread use since the 1970s and is used to image many diseases and injuries.
Using X-rays does carry a small risk. However, to put this into context, a CT scan will deliver approximately the same amount of radiation you would absorb from your normal surroundings in about three years. Another way of looking at this is to say that the benefits of having a scan outweigh the risks associated with it.
If you’ve never had an CT scan you might not know what to expect and this brief guide is designed to answer the questions that might be in your mind.
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've 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.
Using X-rays does carry a small risk. To put this into context, a CT scan will deliver approximately the same amount of radiation you would absorb from your normal surroundings in about three years. Another way of looking at this is to say that the benefits of having a scan outweigh the risks associated with it.
For an abdominal CT you may be asked to drink a liquid to outline the bowel before commencing the examination or you may need a small injection of contrast medium to assist the examination.
During the scan you'll lie on a bed, with the body part under examination placed in opening of the scanner.
The bed then moves slowly backwards and forwards to allow the scanner to take pictures of your body, although it won't actually touch you. The length of the examination depends on the number of pictures and the different angles taken.