Computed Tomography Scans (CT)

CAT scan machine

CT stands for Computed Tomography.

  • It is like a CXR in that it also uses ionising radiation to produce pictures of the chest.
  • It uses a higher dose of radiation to produce more detailed pictures.
  • Many thin images are reconstructed by computer to produce a 3-D image of the chest.

What happens during a CT scan?

Like a CXR the person may be asked to wear and gown and to remove anything which may interfere such as jewellery.

An injection of special liquid is often given to the patient through a vein. This is called 'contrast material' and helps to enhance internal organs and vessels to allow more detail to be seen in the images.

  • They will lie on a table which moves them in and out of the scanner.
  • The scanner is sometimes described as a donut or a box and the person goes through the tunnel or hole in the middle of the donut.
  • The scanning usually takes less than a minute.
  • The person must lie still to avoid blurry images.
  • They will be alone in the room but can speak to the technicians as there is a microphone and speaker in the scanner.
  • Clicking and whirring sounds can be heard when the scan is performed but  no moving parts can be seen.

What can a CT scan show?

A CT scan shows more detailed images than a simple X-ray for lung diseases, heart disease or cancer.

  • They can be performed to investigate abnormalities found on a CXR or when symptoms do not get better after a previous CXR which looked normal.
  • They can be used to diagnose and evaluate the severity of lung diseases and monitor if things are getting worse or better.