Positron Emission Tomography (PET)

Positron Emission Tomography (PET) is a medical imaging technique that uses a radioactive tracer to visualize and measure the metabolic activity of cells in the body.

Principle

PET works on the principle of detecting pairs of gamma rays emitted by a positron-emitting radionuclide. The radionuclide is typically injected into the body, where it accumulates in areas of high metabolic activity. As the radionuclide decays, it emits a positron, which then annihilates with an electron to produce a pair of gamma rays that travel in opposite directions.

Procedure

The PET procedure typically involves the following steps:

• A small amount of radioactive tracer is injected into the body, usually through a vein in the arm.
• The patient is then placed on a table that slides into the PET scanner, which is a large, doughnut-shaped machine.
• The scanner detects the gamma rays emitted by the radionuclide and uses them to create detailed images of the body's internal structures.
• The images are then reconstructed using computer algorithms to produce cross-sectional views of the body.

Types of PET Scans

There are several types of PET scans, including:

• F-18 FDG PET scan: This is the most common type of PET scan and uses fluorodeoxyglucose (FDG) to visualize glucose metabolism in the body.
• Nitrogen-13 ammonia PET scan: This type of scan uses nitrogen-13 ammonia to visualize blood flow and perfusion in the heart.
• Oxygen-15 water PET scan: This type of scan uses oxygen-15 water to visualize blood flow and perfusion in the brain.

Clinical Applications

PET scans have a wide range of clinical applications, including:

• Cancer diagnosis and staging: PET scans can help diagnose and stage cancer by visualizing the metabolic activity of tumors.
• Cardiovascular disease: PET scans can help evaluate blood flow and perfusion in the heart, which can be useful in diagnosing coronary artery disease.
• Neurological disorders: PET scans can help diagnose and monitor neurological disorders such as Alzheimer's disease, Parkinson's disease, and epilepsy.

Risks and Side Effects

The risks and side effects of PET scans are generally minimal, but may include:

• Radiation exposure: PET scans involve exposure to small amounts of radiation, which can increase the risk of cancer.
• Allergic reactions: Some patients may experience allergic reactions to the radioactive tracer or other medications used during the scan.
• Claustrophobia: The PET scanner can be a enclosed space, which can cause anxiety or claustrophobia in some patients.