Positron emission tomography (PET) is a nuclear medicine test that uses a radioactive tracer and a special camera to look at organs in the body through metabolic activity. During the test, the tracer is injected to be absorbed and metabolized by cells in the body, emitting positrons. The scanner detects and records the positrons, creating three-dimensional images on a computer.
Through PET scans, physicians are able to detect abnormalities in the body. Areas with a high level metabolic activity are called “hot spots” because they appear more intense on the image than surrounding tissue. Areas of low metabolic activity appear less intense and are sometimes referred to as “cold spots.” Using these images and the information they provide, physicians evaluate how well organs and tissues are working.
A PET scan is done to:
- Study the brain’s blood flow and metabolic activity. A PET scan can help a doctor find nervous system problems, such as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, amyotrophic lateral sclerosis (ALS), Huntington’s disease, stroke, and schizophrenia.
- Find changes in the brain that may cause epilepsy.
- Evaluate some cancers, especially lymphoma or cancers of the head and neck, brain, lung, colon, or prostate. In its early stages, cancer may show up more clearly on a PET scan than on a CT scan or an MRI.
- Help a doctor choose the best treatment for cancer. PET scans may also be done to see whether surgery can be done to remove a tumor.
- See how advanced a cancer is and whether it has spread to another area of the body (metastasized).
- Find damaged heart tissue, especially after a heart attack.
Help choose the best treatment, such as coronary artery bypass graft surgery, for a person with heart disease.