A CT scan is a computerised tomography scan. It uses X-rays and a computer to create detailed images of the inside of your body.
CT scans are also sometimes known as CAT scans, which stands for computerised axial tomography.
During a CT scan, you will usually lie on your back on a flat bed. The CT scanner consists of an X-ray tube that rotates around your body. You will usually be moved continuously through this rotating beam. The rays will be analysed by a detector on the opposite side of your body.
Unlike an MRI scan, where you are placed inside a tunnel, you should not 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 10 to 30 minutes, depending on the part of your body being scanned.
Read more about how a CT scan is performed.
When CT scans are used
CT scans can be used to diagnose and monitor a variety of different health conditions including brain tumours, certain bone conditons and injuries to internal organs such as the kidneys, liver or spleen.
They are also often used to look inside the body before another procedure takes place, such as radiotherapy treatment or a biopsy (where a small tissue sample is taken so that it can be examined under a microscope).
Read more about when you might need a CT scan.
Your results
CT scans are usually carried out on an outpatient basis, which means that you will be able to go home on the same day as the procedure.
The results of your scan will not be available immediately. A computer will need to process the information from your scan, which will then be analysed by a radiologist (a specialist in interpreting images of the body).
After analysing the images, the radiologist will write a report and send it to your specialist or GP. This usually takes a few weeks.
Safety
CT scans are safe procedures and, in most cases, the benefits of having a scan outweigh any potential risks.
A CT scan does expose you to radiation. The amount is small and will not cause you any harm. However, CT scans are not recommended for pregnant women because there is a small risk that the X-rays that are used could harm the unborn baby.
Children are also more at risk than adults are from developing a build-up of radiation. Therefore, a CT scan will only be recommended if a child has a serious condition that puts them at greater risk.
Read more about the risks of CT scans.
