Positron emission tomography (PET) scanner

During a positron emission tomography (PET) scan, a healthcare professional injects a small amount of a radioactive substance called a tracer into a vein. You then lie on a narrow table that moves into a large, ring-shaped machine. The scanner makes pictures that show how cells and tissues take up the tracer. A PET scan can help diagnose conditions such as cancer, heart disease and brain conditions. The test also may be done to help plan treatment.