A CT or CAT scan is often the term used to describe a radiological test known as 'computerized tomography' or ‘computed axial tomography’. The CT scanner is a doughnut shaped machine that uses advanced x-ray technology to take pictures of cross-sections of your body, called ‘slices’.

How is a CT scan performed? A nurse will take you into the CT scan room where you will be asked to lie down on the CT bed (usually on your back). You should get as comfortable as possible because it is very important that you do not move during the test. CT examinations differ depending on your medical problem and the part of your body being studied.

The radiologist will plan an examination that suits your diagnostic needs; for example, if you're brain is being studied, a series of pictures will be taken from your lower neck to the top of your head. During the study, you may be asked to hold your breath so the pictures will not be blurred. The machine will make some noise, so don’t be alarmed and the bed may move slightly after each picture. As part of your test, before or during the study, you may be given an injection (by a nurse, technologist or doctor,) of a contrast agent. This allows the radiologist to obtain clear images of your organs.

Your CT scan is tailored to your individual requirements, so don't be alarmed if your examination is different from one you have had before, or if some additional pictures are taken after the first series are completed. From start to finish the picture taking part of the test usually lasts only 10 to 15 minutes. However it takes some time to set up the equipment so the test can feel like it is taking much longer.

Once the CT scan has been completed and the information has been collected, you'll be able to leave and go about your normal activities.

Your examination results will then be reviewed by a radiologist who specializes in this type of imaging. Your results are then sent you doctor or neurologist.

Is a CT scan dangerous? The test itself is completely painless. You'll be asked to lie quietly on the CT scanner ‘bed’ during the study. Depending on the type of study being done, you may be injected with a contrast material. This part of the procedure may be slightly uncomfortable.

Often contrast agents contain iodine, which can cause allergic reaction in some individuals. Be sure to tell the radiologist or nurse if you have had an allergic reaction to iodine or contrast agent in the past, or if you have any other allergies.

CT scanners use x-rays; because x-rays can harm a developing fetus, you should tell your doctor if you are, or even think you may be pregnant before preparing for the CT scan. Even if you haven't told the doctor, be certain to tell the radiographer who prepares you for the study. A CT scan can see inside the brain and other parts of the body, and into areas that cannot be seen on regular X-ray examinations. The CT scanner makes it possible to diagnose certain conditions earlier and more accurately than with other imaging tools.