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What it is: Positron Emission Tomography (PET) is an imaging technology that can help reveal how tissues and organs are functioning. 

How it works: It involves giving patients a small amount of radioactive material, which then accumulates in areas that have higher levels of chemical activity. This shows up on the scan as bright spots, typically corresponding to areas of disease. 

Why it is used: PET can be used to diagnose neurological conditions, heart disease, cancer and brain disorders.