A PET scan refers to the use of a Positive Emission Tomography machine. This type of machine uses a functional imaging technique that is meant to observe metabolic processes in three dimensions through the measurement of gamma rays that are indirectly emitted by a positron-emitting radionuclide that had been previously introduced into the body.
Patients are injected with a substance that has radioactive tracers that make the PET machine able to see how organs are working and if anything is wrong. PET scans can measure things like blood flow, glucose metabolism, and oxygen levels. A common use of PET scans is in screening cancer patients for signs of metastasis (the cancer spreading to other organs) but it can also check for other diseases like heart disease, brain disorders, and issues with the nervous system.