Positron emission tomography in experimental perinatology.

Positron emission tomography (PET) is a new tracer technique by which short-lived radionuclides, such as 11C are used for labeling drugs, amino acids and other compounds. The concentration in the various organs is determined non-invasively after I.V. injection. Positrons, emitted by 11C attract an electron, and the two masses are annihilated by emitting photons. These can be registered by external detectors. Measurement of the radioactivity per volume of tissue as a function of time is accomplished by computerized processing of the data. The PET technique may be used for studies of the kinetics of the injected compound in different organs of the body. However, PET registers only the total radioactivity meaning that the measured 11C-radioactivity represents the sum of the parent compound and the radiolabelled metabolites. Chemical and radiochemical analyses in various body fluids may then help to interpret the PET images.