A study of scintillation beta microprobes

Several types of scintillation microprobes have recently been developed to directly measure positron activity from radiotracers in live animals. These probes consist of either a small LSO crystal or plastic scintillator coupled to an optical fiber which is read out with a photomultiplier tube operated in a single photon counting mode. Each type of probe has certain advantages and disadvantages in its ability to detect positrons and reject background gamma rays due to their different relative conversion probabilities and light output of each scintillator. In this paper, a comparison has been made of the relative detection efficiency of these two types of probes for positrons and gamma rays, and in their ability to localize positron decays using pulse height discrimination. Results are also given on the use of the microprobe on live laboratory animals.