Positron Emission Tomography

Positron emission tomography, or PET, is a radiotracer-based medical imaging technique commonly used for tumor detection, determining the extent of metastases, evaluating heart ailments like impaired blood supply, and studying  neural activity in the brain.

To perform a PET scan, the patient is most often injected with a radioactive tracer, a biological molecule bound to a positron-emitting isotope such as carbon-11, oxygen-15, or fluorine-18.

Once in the body, these radiotracers accumulate inside the tissue or the cells where they have higher affinity. For instance, fluorodeoxyglucose or FDG accumulates more in tumors due to their higher metabolic activity.

The unstable radioactive fluorine decays, emitting positrons - the positively charged antiparticle of electrons. The positrons combine with nearby electrons resulting in an annihilation reaction and emit two photons of 511 keV energy in opposite directions.

The PET detector collects millions of these annihilation events and, using complex computing algorithms, reconstructs the images of tracer distribution in the area under study.