Glossary

Positrons are an elementary particle, i.e., subatomic particle.  Positrons have a mass and a magnitude of charge identical to an electron, but positrons exhibit a positive charge.   For this reason positrons are also sometimes called positive electrons, and are actual antimatter.

Tomography is a a method of producing (1) either detailed images of a plane section of a solid object, such as the body, while blurring out the images of other planes (2) a three-dimensional image of the internal structures of a solid object (e.x. the human body) by the observation and recording of the differences in the effects on the passage of waves of energy impinging on those structures.  It is also called called also stratigraphy.

Gamma Rays are highly penetrating electromagnetic rays which are not appreciably deflected by a magnetic or electric fields.  Like visible light, they contain photons.  Gamma rays are emitted by radioactive substances during radioactive decay..