Labelling a single particle for positron emission particle tracking using direct activation and ion-exchange techniques

Positron emission particle tracking (PEPT) is a non-invasive technique used for obtaining dynamic information within multiphase systems. It involves tracking a single radioactively labelled tracer particle. The tracking efficiency and representative of PEPT data are crucially dependent on the amount of radioactivity labelled in a single particle, as well as the physical and chemical properties of a tracer. This paper will discuss the effect of tracer properties on PEPT data and two labelling techniques, direct activation and ion-exchange, in detail. In direct activation, particles are directly bombarded using a 33 MeV 3He beam. A few of the oxygen atoms in the particles are then converted into 18F radioisotope. Direct activation can be used to label a particle with a size range from 1 to 10 mm, but the material must be able to resist a high temperature. The ion-exchange technique can be used to label smaller resin particles with a size ranging from 60 to 1000 μm. The radioactivity labelled in a single resin bead is controlled by ion-exchange properties of the resin material, anions present in the radioactive water and processing time.