A positron is a positively charged, with a resting energy of at least 511 keV, subatomic particle. A positron is the antiparticle of an electron, identical in mass and spin.
Positrons can be generated by positron decay or pair production.
Positron emission tomography detects positrons from the decay of radioactive tracers.

See also Beta Decay.

[Beta Plus Decay] If an atom is unstable because there are too many protons in the nucleus, a proton is converted into a neutron and a positron is emitted. The atomic mass of the atom stays unchanged, but the number of protons increases by one, the number of neutrons decreases by one, which transforms the atom to a different element.

See also Beta Decay.

Camera used to image positron-emitting radionuclides in patients.

When an electron collides with its antiparticle, a positron, causing both elements to be completely destroyed and in most cases resulting in the emission of gamma rays.

See also Electron, Positron and Antiparticle.

(ACD) Caused by positron decay and positron annihilation two photons are emitted each with an energy of 511 keV in opposite directions. The simultaneous detection of these two photons, by two detectors indicates that a positron annihilation occurred at the line of response (LOR), the path between the two detectors.
In PET imaging the annihilation coincidence detection is used to localize the tracer, e.g. F18.

See also Positron Decay and Electron Positron Annihilation.