Three-layer GSO depth-of-interaction detector for high-energy gamma camera

Yamamoto, Seiichi*; Watabe, Hiroshi*; Kawachi, Naoki; Fujimaki, Shu; Kato, Katsuhiko*; Hatazawa, Jun*

Using Ce-doped GSO of different Ce concentrations, three-layer depth-of-interaction (DOI) block detectors were developed to reduce the parallax error at the edges of a pinhole gamma camera for high-energy photons. GSOs with Ce concentrations of 1.5 mol%, 0.5 mol% crystal, 0.4 mol% were selected for the DOI detectors. These three types of GSOs were optically coupled in the depth direction, arranged in a 22 22 matrix and coupled to a flat panel photomultiplier tube. With these combinations of GSOs, all spots corresponding to GSO cells were clearly resolved in the position histogram. Pulse shape spectra showed three peaks for these three decay times of GSOs. The block detector was contained in a tungsten shield, and a pinhole collimator was mounted. With pulse shape discrimination, we separated the point source images of the Cs-137 for each DOI layer. The point source image of the lower layer was detected at the most central part of the field-of-view (FOV), and the distribution was the smallest. The point source image of the higher layer was detected at the most peripheral part of the FOV, and the distribution was widest. With this information, the spatial resolution of the pinhole gamma camera can be improved. We conclude that DOI detection is effective for pinhole gamma cameras for high energy photons.