48V radionuclidic impurity in product streams from liquid cyclotron targets with titanium windows

Vanadium-48, a positron emitter with a 16.0 day half-life, was observed in the aqueous product stream from a liquid cyclotron target equipped with a titanium window, a type of target system commonly used for preparing [13N]NH3 at PET centers. The amount of 48V activity is directly related to bombardment time and beam current. It is apparently present as vanadate ion, and it is efficiently removed by anion exchange cartridges. More generally, it is likely that the specie would be present in the product stream of any titanium-window-equipped liquid target which contains water and which is bombarded with protons or deuterons. Incidental to the 48V investigation, was quantitation of 18F in the system under study.