positron counter / digital / electronic

With more and more sophisticated nuclear medicine applications, positron (β+) counting has become of increasing interest. Positrons are unique in that their lifetime is measured in picoseconds. Once they interact with a nearby electron, they give rise to two directly-opposed 511 KeV gammas ("annihilation radiation"), one or both of which then may be counted with a conventional gamma counter. Today, 11C and 18F are the β+-emitters of greatest interest. Produced at high activity levels with a cyclotron, their relatively short half-lives – 11C (t½ = 20.4 min), 18F (t½ = 110 min) – necessitate fast chemical processing and almost instantaneous utilization.
As production methods have improved, and with chemistry automated, it has become possible to rapidly synthesize and employ more complex molecules. The natural progression has then been to study metabolism. With the time for synthesis, the time within the biological system, the time for metabolite isolation, and the short half-lives, low-level β+-counting is suddenly a requirement. The Posi-RAM has been developed specifically for that need.