What is meant by PET scan?

SPECT= single photon emission computed tomography PET=positron emission tomography PET is a functional imaging technique that is used to observe metabolic processes in the body as an aid to the diagnosis of disease. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active moleculeThe common molecule used is fludeoxyglucose (FDG), an analogue of glucose(Ref: Grainger and Allison&;s diagnostic radiology 6th edition, page 123)