A Multi-Crystal Positron Camera

Abstract

A multicrystal positron camera designed for use with radionuclides produced with a medical cyclotron is described. The camera uses coincidence techniques for collimation by detecting the positron annihilation radiation. Typical radionuclides are 11C, 13N, 15O with half lives of 20, 10, and 2 minutes, respectively. The principal object of the design is to achieve a data rate capacity to 5 × 104 coincidence events per second, as well as high sensitivity and resolution. This will allow time sequential images of fractional second duration. Each of the camera's two identical detectors consist of a planar array of 127 small NaI(Tl) crystals viewed by an array of 72 phototubes. Timing signals are derived from the phototubes and are subsequently used to identify 2549 crystal pairs. The coincidence data is stored in a magnetic-core memory and used for a local data display; alternatively data may be transferred under program control to a PDP-9 computer. The sensitive field area is 27 cm × 30 cm and the spatial resolution is less than 1 cm at the midplane. The camera is currently being used for a number of clinical applications.