A positron emission tomography, also known as a PET scan, uses radiation to show activity within the body on a cellular level.
It is most commonly used in cancer treatment, neurology, and cardiology.
Combined with a CT or MRI scan, a PET scan can produce multidimensional, color images of the inside workings of the human body.
It shows not only what an organ looks like, but how it is functioning.
A PET scan is used to diagnose certain health conditions, to plan treatment, to find out how an existing condition is developing, and to see how effective a treatment is.
Fast facts on PET scans
Here are some key points about PET scans. More detail is in the main article.
PET scans are often used to diagnose a condition or to track how it is developing.
Used alongside a CT or MRI scan, it can show how a part of the body is working.
PET scans are often used to investigate epilepsy, Alzheimer’s disease, cancer, and heart disease
A scan is not painful, but patients should not consume any food for at least 4 to 6 hours before a scan. They should drink plenty of water.
How it works
PET scans demonstrate the physical state and function of organs.
In a PET scan, a machine detects radiation that is emitted by a radiotracer.
A radiotracer consists of radioactive material that is tagged to a natural chemical, such as glucose.
This radiotracer is injected into the body, where it travels to cells that use glucose for energy.
The more energy a group of cells needs, the more the radiotracer will build up in that location. This will show up on images that are reconstructed by a computer.
The cells, or activity, will show up as “hot spots” or “cold spots.”
Active areas are bright on a PET scan. They are known as “hot spots.”
Where cells need less energy, the areas will be less bright. These are “cold spots.”
Compared with normal cells, cancer cells are very active in using glucose, so a radiotracer made with glucose will light up areas of cancer.
A radiologist will examine the image produced on the computer, and report the findings to a doctor.
An example of a glucose-based radiotracer is fluorodeoxyglucose (FDG). In FDG, radioactive fluoride molecules are tagged to glucose to make a radiotracer. FDG is the radiotracer most commonly used today.
Instead of glucose, oxygen can be used.
PET scans are an important part of the diagnostic process in cancer and epilepsy, and can directly inform the next stage of treatment.
PET scans are often used with CT or MRI scans to help make a diagnosis or to get more data about a health condition and the progress of any treatment.
While an MRI or CT scan shows how part of the body looks, a PET scan can reveal how it is functioning.
PET scans are commonly used to investigate a number of conditions.
Epilepsy: It can reveal which part of the brain the epilepsy is affecting.
This can help doctors decide on the most suitable treatment, and it can be useful if surgery is necessary.
Alzheimer’s disease: PET scans can help diagnose Alzheimer’s disease by measuring the uptake of sugar in specific parts of the brain.
Brain cells that are affected by Alzheimer’s tend to use glucose more slowly than normal cells.
Cancer: PET scans can reveal the presence and stage of a cancer, show whether and where it has spread, and help doctors decide on treatment.
A PET scan can give an idea of how well chemotherapy is working, and it can detect a recurring tumor sooner than other techniques.
Heart disease: A PET scan can help detect which parts of the heart have been damaged or scarred, and it can help identify circulation problems in the working of the heart.