Computerised tomography (CT) scans provide information that doctors can use to help diagnose medical conditions.
CT scan results can confirm or rule out a suspected diagnosis. They can also sometimes help identify conditions that were not suspected.
Unlike other imaging techniques, such as X-rays, CT scans can provide detailed images of many types of tissue, including bone, lung tissue, soft tissue and blood vessels.
Types of CT scan that can be used to investigate particular areas of the body include:
head scans - these can be used to check for suspected brain tumours and bleeding or swelling of the arteries; they can also be used to investigate the brain after a stroke
abdominal scans - these can be used to detect tumours and diagnose conditions that cause internal organs, such as the liver, kidneys, pancreas, intestines or lungs, to become enlarged or inflamed
vascular scans - these can be used to assess conditions that affect the blood flow to different parts of the body
bone scans - these can be used to assess bone injuries and disease, particularly in the spine
CT scans are often used after serious accidents to look for internal injuries, such as tears in the spleen, kidneys or liver.
They're also sometimes used to prepare for further tests and treatments. For example, as CT scans can identify both normal and abnormal tissue, they can be useful when planning radiotherapy treatment.
CT scanning can also act as a guide during a needle biopsy (where a sample of tissue is taken so it can be examined more closely).
CT scan screening
In recent years there have been concerns that in some cases CT scans have been used unnecessarily. Some private medical companies offer CT screening as a way of detecting conditions in people who don't have any symptoms or significant risk factors for a disease. This type of screening can be expensive and put you at unnecessary risk.
CT scans shouldn't be used to give you peace of mind if you don't have any symptoms. A scan may be recommended if you have symptoms caused by an injury or illness that needs to be investigated. However, you should only have a CT scan following a medical referral.
The Department of Health asked a group of experts to investigate the risk of CT scans in healthy people, such as those who decide to pay for a scan as part of a private health assessment.
In 2007, the Committee on Medical Aspects of Radiation in the Environment (COMARE) produced a report outlining a number of recommendations on the use of CT scans for screening.
The report recommended that all radiation exposure and equipment used for exposure should be tightly controlled by certain regulations both in the NHS and commercially.
It also recommended that all private sector organisations offering CT screening should provide comprehensive information about a person's eligibility for screening and the dosage of radiation used.
For full details of all the recommendations, read the COMARE report (PDF, 549kb).