These Gamma Detectors are used for medical, military and security purposes. They comprise one or more scintillation crystals to convert gamma radiation into light. They further comprise one or more highly sensitive light detectors.
One application for Gamma Detectors is in the field of Positron Emission Tomography (PET), a nuclear medicine imaging technique that produces a three- dimensional image of functional processes in a human or animal body. The detection is based on positrons emitted by a radionuclide, a so called tracer, which tracer is introduced into the body together with a biologically active or tolerable molecule. During decay, the tracer emits a positron which travels for a short distance until it interacts with an electron. The encounter annihilates the positron and the electron in a so-called annihilation process and produces a pair of gamma photons which are emitted in opposite direction.
These gamma photons enter a scintillation crystal where they are converted into weak light flashes which are detected by the light detector.
Patent specification (external link)