Initial Characterization of a Multi-Wire Proportional Chamber Positron Camera

Initial results of a research and develo~ment effort on a positron camera utilizing 48 x 48 cm multiwire proportional chambers for dete'cting the annihilation photons that follow positron decay are described.These photons are detected in the chambers by, the photons' interaction with specially configured lead converters placed in close proximity to the chamber wire planes, and the coordinates of the interactions are localized by delay line electronics.A spatial resolution of 6 mm FWHM and.a resolving time width of 350 nanoseconds have been achieved.Present sensitivity is of the order of 675 counts/min-~Ci, with a maximum data rate of 20K counts/min.Scattering medium in the field of view does not significantly degrade performance.Initial in vivo images demonstrate the potential of this camera-.-'-.