Positron emission tomography

Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, regional chemical composition, and absorption. In clinical practice it is used to diagnose and manage cancer treatment, in cardiology and cardiac surgery, and in neurology and psychiatry.

Source: Wikipedia — Positron emission tomography (CC BY-SA 4.0)