What is the test used for?

Computerised tomography (CT) is used to look at the internal structures of the body. Both soft tissues (e.g. brain, liver, kidneys, lungs) and bone can be seen. The images are cross-sections of the body, but the CT computer can generate a great variety of images, depending on what the doctor is looking for.

The Mater CT scanner is a multi-slice Toshiba Aquilion.

What is the preparation for the test?

This depends on the area of the body being examined. You may be asked to fast (no solid food, and only clear liquids) for 2–4 hours before the procedure. If the examination is of the abdomen, you may be asked to arrive 1 hour before the scan to drink a thin Barium liquid, which outlines the bowel.

When you go into the CT room, you may also be asked about any history of allergy, or what medications you are taking.

Will I have to undress?

For a scan of the head, arms or legs, you are generally not required to undress, but may be asked to remove jewellery, hairclips, dentures etc. These items show up too well on x-ray and can be confusing to interpret, or they may hide abnormalities.

For most other scans, you will be asked to remove most of your clothes, but may keep wearing your underpants. You will be asked to change into a cotton gown.

Where will I be for the test?

You will be asked to lie on the CT table, which as the name implies, is fairly hard. We can use pillows and foam pads to make things more comfortable for you, and may use pads or Velcro straps to help keep an area of the body still for the scan. The CT table will move during the scan, but nothing will touch you. The table moves into or out of the scanner, which is a very short tunnel. The tunnel is not enclosed, and only a small part of your body will be in it at any time.

Most examinations are performed with you lying on your back, although occasionally we ask you to lie face down.

How is the test done?

CT scanners are very specialised x-ray machines. As you move through the scanner, x-rays are taken and a powerful computer builds a very detailed image of the internal structure of the part of the body being examined.

To enhance the images, you may be given an injection of x-ray contrast, just before or during the scan. This injection highlights the blood supply to the organs of the body. The contrast is given via a small needle in the arm or hand. The needle is about the size of that used when blood tests are taken. The injection contains an iodine compound. It is important to tell the CT staff if you have any allergy to x-ray contrast. The injection may make you feel warm for a few minutes, and also give you a metallic taste in the mouth. These feelings are quite normal, although many people experience nothing at all. You may be asked to hold your breath during the scan, but only for 15 or 20 seconds. This is because breathing will blur the images.

How long will it all take?

Most CT appointments are for 20 minutes, although for many scans, you will only be on the table for 5 to 10 minutes. The rest of the time is for explaining the procedure, getting you changed, getting you on and off the table.

And after the test?

If you have had barium drinks, drink plenty of clear fluids over the next day to wash it through. You may eat and drink as normal. If you have had an x-ray contrast injection, there should be no lasting effects, although if you do experience anything unusual following the scan, please tell one of the staff so the doctors at Mater Imaging can see you.

Does the test use radiation?

Ionising radiation is used.