Abstract

PET is a unique technique wich provides molecular imaging of biological function in vivo. The main positron emitters used in PET are 15O, 13N, 11C, 18F. These isotopes can be easily incorporated into biological substrates (glucose, H2O, NH3, CO2, O2 ) and pharmaceuticals, without altering their biological activity. This has made PET a very useful tool in the field of research, and originally it was mainly used for this purpose. However, it has become apparent that PET can also provide important diagnostic information in the clinical evaluation of individual patients. The basic pharmaceutical used in clinical  work is 18 F- FDG. The first application was focused to the brain and the heart. In the late 1990s it became apparent that FDG-PET imaging was substantially superior to conventional techniques in diagnosing, staging, and monitoring response to treatment, as well as in detecting recurrence in a variety of cancers. After that started rapid increase of using FDG-PET in daily clinical practice. Thereafter PET was combined with CT. PET/CT merges functional (PET) and structural (CT) information into single scanning techniques, improving lesion localization and interpretation accuracy.