ABSTRACT
Positron-emission tomography (PET) has developed into a leading technology for the in vivo assessment and investigation of physiological function and pathophysiology. The existence of positrons was initially postulated and confirmed in the early 1930s.1,2 Subsequent demonstration of artificially producible radioactive atoms and the invention of the cyclotron paved the way for the development of positron-emission tomography.3,4 Invention of the scintillation radiation detector was quickly followed by the development of the first PET scanners in the late 1950s. The first medical cyclotron was introduced at the Hammersmith Hospital (London, U.K.) (see Ter-Pogossian, M., and Wagner, H., for reviews).5,6
The basis of PET derives from the release of a positron (positive electron) from a decaying radiotracer. The subsequent annihilation reaction resulting from collision with an electron results in the production of two photons. These photons, travelling in opposite directions, are subsequently detected and used for source localization via reconstruction algorithms. The result is the PET image. The applicability of PET, in studying physiological and pathophysiological processes, stems from the ability to incorporate radiotracers in to various biological substances. Thus, the fate of such substances can be tracked and information derived regarding the pathways involved. Therefore, the advantage of PET is its ability to study function in contrast to more conventional imaging technologies that focus on structure. Recent and ongoing technological advances, along with novel ideas, have broadened the scope of usefulness and feasibility of PET, allowing a predominantly research-oriented tool to be increasingly applicable clinically.
