CAT scan

Computed Tomography (CT)

A CT scan is a special type of x-ray carried out by a radiographer that takes pictures of cross sections or slices of organs and structures in the body. Each scan or slice when put together forms a 3-D picture of the body. A CT scan offers different views of different tissue types including liver, pancreas, bones soft tissue and blood vessels. CT scans are commonly performed on the head, chest and abdomen and involve exposure to radiation in the form of x-rays however; this is kept to a minimum. The patient lies on a couch which slides through a narrow doughnut as the images are obtained.


A CT scan offers a more detailed image that that of a plain x-ray and allows quick, accurate diagnosis of a number of medical and surgical conditions.

The Procedure

Patients are encouraged not to eat anything for up to four hours prior to the scan however, they can drink water. Strenuous exercise and caffeine should be avoided on the day of the scan and it is advisable to arrive in plenty of time in order to allow the heart to rest.

Most scans take approximately 30 minutes but occasionally a scan of the abdomen can take up to one hour. The procedure is painless.

During the scan patients are asked to lie very still on the CT table and are sometimes attached to an ECG monitor that shows the heart rate. For certain scans patients will be given an injection or drink of contrast agent (a radio-opaque dye) which allows the radiologist to see parts of the body more clearly. Scans of the chest, abdomen or pelvis requiring the injection of contrast will take longer than non-contrast scans.

If a patient is pregnant or there is or possibility of being pregnant, the radiographer should be informed prior to the scan. If another test with no ionising radiation can be performed then this would be preferable.

Patients should continue to take their current medication unless they are advised otherwise and diabetics should inform the Radiology Department prior to a scan which medication they are taking.

It is helpful if patients bring any previous x-rays with them.

Possible Side Effects

The injection can make some patients feel hot and give them a strange taste in the back of the throat. This is quite normal and quickly passes. Occasionally other side effects such as feeling sick, skin reactions and very rarely anaphylaxis can occur. For this reason patients are asked to stay in the department for 15 minutes after their scan to observe for this. If delayed reactions develop after leaving the hospital, then patients should seek medical attention.