Optimising the design of a large-area positron camera based on BaF2-TMAE/MWPC technology

A prototype annihilation photon detector has been constructed by the RMH/ICR/RAL collaboration based on the coupling of a 50 × 50 × 8 mm3 BaF2 scintillator to a low pressure TMAE filled multiwire proportional chamber. Its design is undergoing optimisation and currently achieved performance is 8 mm FWHM spatial resolution, 12 ns time resolution and 19% efficiency.The problems associated with scaling up this technology for a clinical PET system were investigated using Monte Carlo techniques. The size of the required detectors (600 × 400 mm2) will result in the use of tiles of BaF2. A comparison between a single slab and a 6 × 4 array of 16 mm thick crystals was made and the errors introduced were studied. Spatial resolution was degraded 40% axially and 27% radially/tangentially by multiple crystals. However, the imaging of distributed sources demonstrates that in any practical situation quality degradation comes primarily from scattering. Further studies to determine the distribution of scatter expected from the proposed detector are outlined.