CT scans (CAT scans)
What is a CT scan?
CT stands for computed tomography, also called computerised axial tomography (CAT). CT is a procedure for creating a detailed picture of the interior of part of the body using a series of X-rays. Like most ordinary X-rays, it is a painless procedure.
If you knew that something was hidden inside a loaf of bread the obvious way to find it would be to cut the loaf into slices. In just the same way, a CT scan takes a series of X-rays of different 'slices' of the part of the body being examined. The information obtained is processed by a computer, which can create sets of pictures from different directions and also 3-dimensional pictures.
Having a CT scan
A CT scanner is shaped like a large doughnut lying on its side. To have a CT scan, you lie on a moving table that slides inside the "doughnut hole" of the scanner. You must lie still while various parts of the scanner move around taking the X-ray pictures. You may hear whirring and clicking noises. Some people find being inside the machine slightly unpleasant, especially if they have claustrophobia (fear of confined spaces). However, the whole procedure usually takes only 10 to 20 minutes.
For some scans you may be given an injection of a contrast dye to give a clearer picture or additional information. For CT scans of the stomach and intestine you may be asked to drink a contrast dye.
Benefits and risks of CT scans
The CT scan has replaced many uncomfortable and invasive tests that were done in the past. It allows doctors to diagnose accurately and treat patients more effectively. CT scans are very useful for:
- diagnosing a wide variety of different conditions, including internal injuries and bleeding after accidents;
- detecting and monitoring diseases such as cancer and heart disease; and
- guiding surgery and other procedures.
Like all X-rays, CT scans expose you to radiation. In fact, because CT scans involve a series of X-rays, they generally expose you to far more radiation than a single X-ray. This can very slightly increase your risk of cancer. It also means CT scans are generally unsuitable in pregnancy.
Your doctor can help you weigh up the risks and benefits of having a CT scan. Your doctor can also discuss whether there are any suitable alternatives in your case, such as magnetic resonance imaging (MRI).
Last Reviewed: 16 June 2010
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