How does a CT Scanner work?

A CT scanner produces images known as tomographs, which offer a much more detailed image than X-rays and permit doctors to see images of the interior organs and structures of the body.

The CT scanner is ring-shaped, and has a motorised bed that moves through it slowly. The generated images will ultimately be sent to a computer for analysis. The X-ray revolves around the patient, scanning and creating images of different areas of the body. This forms a complete picture of the body, which shows a cross-section of the inside of the body that many people refer to as ‘slices.’

The cross-sectional images enable doctors to diagnose a number of different conditions and diseases. They can also show inflammation, bleeding, damage to internal organs and abnormal structures, such as tumours.

How are the images generated?

The images are generated by X-ray scanners, which capture images as the motorised bed moves through the scanner. A radiographer operates the scanner and they will ensure that the bed is in the correct position. Different parts of the body can be scanned, and the bed moves slowly to allow many diverse images to be taken. The radiographer may ask the patient to breathe in or hold their breath at certain points during the scan.

In many cases, a contrast medium is used to make the scan images clearer. Contrast medium is dye that is injected, swallowed or given via an enema to allow doctors to distinguish between blood vessels and other internal structures. In very rare cases, people experience an allergic reaction to the contrast medium. If you have any allergies or have experienced an allergic reaction to a dye or Iodine before, then it is advised that you tell the radiographer before you have your scan.

Once the images have been generated, they will appear on the computer screens as detailed 3D images of the inside of the body. These can then be analysed by radiologists and other medical specialists.

How long does the scan take?

In most cases, a normal scan takes around 30 minutes. However, the helical (spiral) CT scans are much quicker and can generate images in just a few minutes. Patients are usually free to go home immediately following the scan, with results normally available around 2 weeks after the scan.