Development of a high resolution positron CT for animal studies

A single ring high resolution positron CT for animal studies was developed which utilizes 64 gridded rectangular photomultipliers (13mm square) and 128 rectangular Bismuth Germanate crystal (4mm wide, 10mm high and 20mm long). A photomultiplier is incorporated with a grid near the photocathode which controls photoelectron transport of half part of a tube. This enables us the identification of the fired crystal out of two coupled to a photomultiplier. Detector ring, animal port and field of view diameters are 265, 135 and 128mm, respectively. Detector arrangement was determined by POSITOLOGY. The spatial resolutions in fwhm after unfolding source spread (2mm dia.) were 2.2mm at center and 3.3mm (tangential) and 3.6mm (radial) at 60mm from the center. Hardware out-of-FOV event rejector was implemented which rejects events outside the field of view and reduces event rate by a factor of 3 in the case of calibration measurements