CT Scan

CT scan

Also known as a CAT scan, is a specialised X-ray test. It can give quite clear pictures of the inside of your body. In particular, it can give good pictures of soft tissues of the body which do not show on ordinary X-ray pictures.

CT stands for computerised tomography, and CAT for computed axial tomography. The CT scanner looks like a giant thick ring.. You lie on a couch which slides into the centre of the ring until the part of the body to be scanned is within the ring. The X-ray machine within the ring rotates around your body. As the couch moves slowly through the ring the X-ray beam passes through the next section of your body. So, several cross-sectional pictures (slices) of the part of your body being investigated are made by the computer. Newer scanners can even produce 3-dimensional pictures .

What is a CT scan used for?

A CT scan can be done on any section of the head or body. It can give clear pictures of bones. It also gives clear pictures of soft tissues which an ordinary X-ray test cannot show, such as muscles, organs, large blood vessels, the brain and nerves.

The most commonly performed CT scan is of the brain - to determine the cause of a stroke, or to assess serious head injuries. Other uses of a CT scan include:

To detect abnormalities in the body, such as tumours, abscesses, abnormal blood vessels.
To give a surgeon a clear picture of an area of your body before certain types of surgery.
To pinpoint the exact site of tumours prior to radiotherapy.
To help doctors find the right place to take biopsies (tissue samples).

What preparation do I need to do before a CT scan?

It depends on which part of your body is to be scanned. You will be given instructions by the CT department appropriate for the scan to be done. As a general rule, you will need to remove any metal objects from your body, such as jewellery, hair clips, etc. It is best not to wear clothes with metal zips, studs, etc. You may be asked not to eat or drink for a few hours before your scan - depending on the part of your body to be scanned. If you need an injection of contrast, as described below, it may be necessary to stop certain medicines before the procedure.

In some situations, depending on what part of the body is being scanned, one of the following may be needed. For abdominal and pelvic scans you may be asked to have a special drink before the scan. This helps to show up the stomach and bowel more clearly.

For pelvic scans, some fluid may be put into your rectum (back passage).
For pelvic scans, women may be asked to insert a tampon into the vagina.
Sometimes a dye (contrast medium) is injected into the bloodstream via a vein in your arm. The dye may give you a flushing feeling and an odd taste in your mouth, which soon goes.

The CT scan itself is painless. You will be asked to stay as still as possible, as otherwise the scan pictures may be blurred. The scan can take between 5-30 minutes, depending on which part of the body is being scanned.

Can anybody be with me during the scan?

Because the scan uses X-rays, other people should not be in the same room. However, you can talk to them, usually via an intercom, and you will be observed at all times on a monitor.

Some people feel a little anxious or claustrophobic in the scanner room when they are on their own. A mild sedative may be offered if you are particularly anxious.

Are there any possible complications?

Complications are rare. Rarely, some people have an allergic reaction to the contrast dye which is sometimes used. This can be treated immediately. Very rarely the dye may cause some kidney damage, most commonly in people already known to have kidney problems.

Pregnant women
If possible, pregnant women should not have a CT scan, as there is a small risk that X-rays may cause an abnormality to the unborn child.

Risks of X-ray radiation used in CT scans

CT scans use X-rays, The dose of X-ray radiation needed for a CT scan is much more than for a single X-ray picture, but is still generally quite a low dose. The risk of harm from the dose of radiation used in CT scanning is thought to be very small, but it is not totally without risk. As a rule, the higher the dose of radiation, the greater the risk. So, for example, the larger the part of the body scanned, the greater the radiation dose. And, repeat CT scans over time cause an overall increase of dose. Also, the younger you are when you have a CT scan, the greater the lifetime risk of developing cancer or leukaemia.

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