Optical fiber readout of scintillator arrays using a multi-channel PMT: A high resolution PET detector for animal imaging

We report the results from a new high resolution gamma ray imaging detector designed for use in a positron emission tomography (PET) system dedicated to small animal imaging. The detectors consist of an 8 x 8 array of 2 x 2 x 10 mm bismuth germanate (BGO) crystals coupled by 2 mm diameter double clad optical fibers to a 64 pixel multi-channel photomultiplier tube (MC-PMT). A charge division readout board is used to convert the 64 output channels into four position sensitive signals which determine the crystal of interaction. Measurements with a pair of these detectors demonstrate an intrinsic spatial resolution of 1.4 mm, a coincidence timing resolution of 15 ns and an energy resolution ranging between 35 and 60%. Based on these encouraging results, the design for a dedicated animal PET tomograph is proposed and simulations of this system project a reconstructed resolution of less than 2 mm within a 5 cm diameter transaxial field of view.