FIG. 1

A PET scanner consists of a ring of radiation detectors designed to detect the simultaneously emitted, characteristically back-to-back (180° apart) dual photons that are created by the annihilation of a positron and an electron. Opposing detectors are electronically coupled to form a coincidence circuit. Thus, when separate scintillation events in paired detectors coincide, an annihilation event is presumed to have occurred at some point along an imaginary line connecting the two. This information is registered by a computer and later used to reconstruct images using the principles of computed tomography.

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published 2000