High Resolution Positron Emission Tomography Using Small Bismuth Germanate Crystals and Individual Photosensors

We describe and compare six detector approaches for coupling small bismuth germanate crystals to individual photosensors. 1) Partial coupling of individual crystals to small cylindrical phototubes. 2) Full coupling of individual crystals to small cylindrical phototubes via shaped lightpipes. 3) Coupling of cylindrical phototubes to individual crystals using three sides of the crystals. 4) Full coupling of individual crystals to small rectangular photomultiplier tubes. 5) Full coupling of groups of crystals to multipleanode phototubes. 6) Full coupling of groups of crystals to larger rectangular phototubes with either sense wires, solid state photosensors, or UV sensitive wire chambers for crystal identification. From experimental measurements and Monte Carlo computer simulations we conclude that approaches 5 and 6 are superior in pulse height and timing resolution and are also the best way to read out crystals narrower than 3 mm.