Application of new Burle multipad flat panel PMTs in compact gamma and positron imagers-initial evaluations

We have performed initial evaluations of the new position sensitive flat panel 85001 and 85011 PMTs from Burle Industries for applications in compact gamma and positron imagers. Different sizes of NaI(Tl) and LSO scintillation crystal arrays were coupled to individual PMTs and to arrays of these PMTs. The main challenge with the present mechanical package design of these microchannel plate based PMTs is their rather large (∼1 cm) dead space around the active photocathode field. However, two imaging applications were identified where this limitation can be overcome. In the first case, the arrays of 2×2 and 3×3 PMTs with specially designed optical coupling schemes were built to minimize the effect of the dead space between PMTs. When combined with moderate NaI(Tl) scintillation pixel sizes of 6.6 mm and 10 mm offering adequate practical spatial resolution for a cardiac camera, the obtained response uniformity is satisfactory over the active surface of the detector. Based on this concept, a practical prototype of a compact high rate imaging gamma camera was designed and will be built primarily for fast cardiac applications. In the second potential application, PMT modules can receive scintillation signals via optical fibers with fiber arrangement avoiding dead regions between PMTs arranged in an array, in a ring, etc. At this time a small PET scanner based on this solution is discussed with potential applications to small animal and brain imaging.