Oxygen-18 (18 O, Ω) is a natural, stable isotope of oxygen and one of the environmental isotopes.. 18 O is an important precursor for the production of fluorodeoxyglucose (FDG) used in positron emission tomography (PET). Generally, in the radiopharmaceutical industry, enriched water (H 2 18 O) is bombarded with hydrogen ions in either a cyclotron or linear accelerator, creating …

The eighteenth season of British science fiction television series Doctor Who consisted of seven four-episode serials broadcast from 30 August 1980 with the serial The Leisure Hive, to 21 March 1981 with the serial Logopolis.The season is Tom Baker's final as the Fourth Doctor before his regeneration into the Fifth Doctor (Peter Davison), as well as Lalla Ward's as companion …