A computerised tomography (CT) scan uses X-rays and a computer...

A computerised tomography (CT) scan uses X-rays and a computer to create detailed images of the inside of the body.
CT scans are also sometimes known as CAT scans, or computed tomography scans.
During a CT scan, you'll usually lie on your back on a flat bed. The CT scanner consists of an X-ray tube that rotates around your body. You'll usually be moved continuously through this rotating beam.
The X-rays will be received by a detector on the opposite side of your body and an image of the scan will be produced by a computer.
Unlike an MRI scan, where you're placed inside a tunnel, you shouldn't feel claustrophobic.
The images produced by a CT scan are called tomograms and are more detailed than standard X-rays. A CT scan can produce images of structures inside the body, including the internal organs, blood vessels, bones and tumours.
The scan is painless and will usually take between five and 10 minutes depending on the part of your body being scanned.