Development of a compact and high spatial resolution gamma camera system using LaBr3(Ce)

In small animal imaging using a single photon emitting radionuclide, a high spatial resolution gamma camera is required. However, its spatial resolution is limited by the light output of conventional scintillators such as NaI(Tl). We developed and tested a small field-of-view (FOV) gamma camera using a new scintillator, LaBr3(Ce). The LaBr3(Ce) gamma camera consists of a 2 mm thick LaBr3(Ce) scintillator, a 2 in. 8×8 multi-anode position sensitive photomultiplier tube (Hamamatsu H8500), and a personal computer-based data acquisition system. The LaBr3(Ce) scintillator was directly coupled to the PSPMT and was contained in a hermetically shielded and light tight aluminum case. The signals from the PSPMT were gain corrected, weighted summed, and digitized by 100 MHz free running A-D converters in the data acquisition system. The detector part of the gamma camera was encased in a tungsten gamma shield, and a tungsten pinhole collimator was mounted in front of the detector surface. The intrinsic spatial resolution that was measured using a tungsten slit mask was 0.75 mm FWHM, and the energy resolution was 8.9% FWHM for 122 keV gamma photons. We obtained transmission and emission images that demonstrated the high spatial resolution of the gamma camera system. Approximately two years after the fabrication of the detector, the flood image showed significant distortion due to the change in LaBr3(Ce) of its hygroscopic characteristic. These results confirm that the developed LaBr3(Ce) gamma camera is promising for small animal imaging using a low energy single photon emitting radionuclide if the hygroscopic problem of LaBr3(Ce) will be solved.