A prototype BaF/sub 2//TMAE low pressure multiwire proportional chamber for PET

A prototype annihilation photon detector combining a 50 mm*50 mm*8 mm BaF/sub 2/ scintillator with an MWPC (multiwire proportional chamber) filled with a photoionizing vapor (TMAE) at low pressure has been constructed. The structure of the detector is currently undergoing optimization but its present performance includes 8 mm FWHM (full width at half maximum) spatial resolution, 12-ns timing resolution, and 19% efficiency. It is intended that this technology, once proven, should form the basis for a clinical PET (positron emission tomography) system. In order to cover the large active areas (600 mm*400 mm) of a clinical system, it will be necessary to use tiles of BaF/sub 2/. Crystal boundary effects on image quality, studied using Monte Carlo methods, show degraded spatial resolution by 40% axially and 27% radially/tangentially for a 6*4 array of 16 mm-thick crystals replacing a hypothetical large single crystal. Further studies to characterize the distribution of scattered events in the proposed camera are described.<>