A positron emission tomography (PET) scan is used to produce a detailed, three-dimensional picture of the inside of the body. The images clearly show the part of the body that is being investigated and can also highlight how effectively certain functions of the body are working.
What are PET scans used for?
PET scans are most commonly used to help diagnose a range of different cancers and work out the best ways of treating them. The information provided by a PET scan can show how far a cancer has spread or how well it is responding to treatment.
PET scans are occasionally used to help plan complex heart surgery, such as a heart transplant. They are also used to help diagnose a number of conditions that affect the normal workings of the brain (neurological conditions), such as dementia.
Read more about why you might need a PET scan .
How it works
Before the scan takes place, a radioactive substance, known as a radiotracer, will be passed into your body either by injection, through an inhaler, or in the form of a small tablet or capsule that you swallow.
The tracer gives off particles called positrons that release a type of radiation known as gamma waves, which can be detected by the PET scanner.
By tracking the movement of the tracer, the scanner can build up a detailed image of a number of the body’s functions as well as highlighting areas of the body that have been affected by disease.
Read more about how PET scans work.
You will need to lie on a flat bed which will move you through a large circular scanner.
The scan should not be painful but, for some people, being inside the scanner can be claustrophobic.
Read more about what happens during a PET scan.
Availability
PET scanners are expensive, so they are usually only found at larger hospitals and some specialised research centres.
Due to the lack of availability, PET scans are often only recommended for people with complex health problems. They are not routinely used to diagnose cancer, but they are often used in confirmed cancer cases to check how far the cancer has spread and whether treatment has been effective.
However, PET scans are becoming more widely used by the NHS, with an average of 40,000 PET scans being carried out by the NHS in England each year.
Safety
Any exposure to radiation carries a very small risk of causing damage to tissues and the possibility of triggering a new cancer.
However, the amount of radiation you would be exposed to if you had a standard PET scan would be the same amount you would receive from natural sources, such as the sun (background radiation) over the course of three years.
Increasingly, PET scans are being combined with computerised tomography (CT) scans to provide more detailed images. See PET scan - how it works for more information.
These new types of scanners, known as PET-CT scanners, use higher levels of radiation, which are equivalent to the recommended limit of radiation that anyone working in a nuclear power plant should be exposed to in any given year. However, this increased dose is still well within the acceptable safety limits for radiation exposure.
Read more about the possible risks of PET scans.
