Positrom emission tomography (PET)
What is positron emission tomography (PET)?
Positron emission tomography (PET) is a type of nuclear medicine that measures metabolic activity of cells. PET is actually a combination of nuclear medicine and biochemical analysis. Used mostly in patients with brain or heart conditions and cancer, PET helps to visualize the biochemical changes taking place in the body, such as the metabolism of the heart muscle.
PET differs from other nuclear medicine examinations in that PET detects metabolism within body tissues, whereas other types of nuclear medicine examinations detect the amount of a radioactive substance collected in body tissue in the location under examination.
Until recently, PET procedures were done in dedicated PET centers. The equipment used in these centers is quite expensive. However, new technology allows gamma camera systems (a device to scan patients who have been injected with small amounts of radioactive materials), such as those used in other nuclear medicine procedures, to be adapted for use as PET scanners. The equipment cost is much less, and scans can be done much faster using this new equipment.
How is PET performed?
PET scans can be done on an outpatient basis. It is also possible that some hospital inpatients may undergo a PET examination for certain conditions.
It is not necessary to fast before the examination, however, a patient may be advised to abstain from alcohol, caffeine, some medications, and tobacco.
Although each hospital may have specific protocols in place, generally, a PET scan procedure follows this process:
- The patient lies on a table that slides into the middle of the PET scanner.
- A small amount of radioactive material is injected into the vein.
- The scanner detects gamma rays and maps an image of the area, allowing the physician to see the location of the metabolic process. For example, glucose (or sugar, which the body uses to produce energy), combined with a radioisotope, will show where glucose is being used in the brain, the heart muscle, or a growing tumor.
- The procedure may be expected to last from 30 minutes to 2 hours, depending on the specific type of PET examination the patient is undergoing.