How it works
Before your CT scan, you may be given a dye that will help the scanner ‘see’ the area required more clearly. This may be given as an injection, or swallowed, or on rare occasions given as an enema. The most common of these is the Barium Meal, which is swallowed to aid assessment of the digestive tract.
You will then lie down on a motorised couch, which will be placed inside the scanner. The scanner itself is a large tube, like a doughnut, but unlike an MRI Scan, only the region to be scanned will need to be inside the machine.
Once you have been placed in position, the radiographer will leave the room to avoid over exposure to the X-rays, but you will still be able to talk to them via an intercom.
The couch will then move slowly backwards and forwards to allow the machine to take a selection of image ‘slices’ through the body as X-ray emitters and receivers move around your body taking images from various angles. You will be asked to stay as still as possible during the CT scan, and to breathe gently to avoid blurring the images. Your radiographer may ask you to hold your breath from time to time.
Your body scan will take around half an hour in total, although much of this time will be used for setting up. Each scan image only takes a few minutes to complete. If you are feeling anxious or are worried about staying still for the scan you can ask for a sedative.
After the CT scan you are safe to go home and continue your normal activities. The dye will pass out of your body naturally in due course, although you should help this along by drinking plenty of water. You should receive your results in around two weeks, although this can be speeded up in urgent cases.
There is little risk to children or adults from a CT Scan. The radiation involved is no more than you would experience from background radiation over about three years. However, the risks to infants could be higher and therefore you should not have a CT Scan if you are pregnant, or think you could be.
Nursing mothers are advised to express milk in advance of their CT scan and to avoid contact with their baby for at least six hours afterwards if there has been a dye used in the treatment. In certain circumstances, nursing mothers may need to express and discard their milk for up to twenty-four hours following a scan.
The Spiral CT Scan
The latest advance in CT Scanning technology is the spiral or helix scanner. This gives a continuous scan by moving the X-ray beam around the patient in a corkscrew pattern.
A spiral scan is quicker and more accurate, producing the same body scan results in just a few seconds, reducing the danger of blurring through movement or breathing. Because it is a continuous scan, it also avoids the risk of missing something in between the ‘slices’ of a traditional CT scan.