Development and Performance Evaluation of a 4π View Radiation Imaging System

In nuclear safety, public health and homeland security, detection of radioactive sources is essential. The existing systems have limits in FOV and/or sensitivity. Based on gamma photon event density distribution inside a 3D position-sensitive detector, position of gamma source can be reconstructed with MLEM. The whole system consists of detector, data processing board, panoramic camera and PC. The 3D position-sensitive detector is made of a GAGG crystal array, coupling with two SiPM array on the top and bottom surface. We designed a rotation system to perform the calibration experiment of system matrix. With different radioactive source (99mTc, 18F, 137Cs), dozens of position (θ, φ) are tested to calculate positioning biases. Energy resolution and energy linearity are tested with 137Cs, 60Co, 232Th. The preliminary test of low counts and two point sources imaging has been performed with 99mTc in the experiment. For 99mTc, 18F, 137Cs, mean of positioning bias (PB θ , PB φ ) is (0.81, 0.52), (1.05, 1.07), (2.35, 1.72) and standard deviation of (PB θ , PB φ ) is (0.55, 0.36), (1.02, 1.06), (1.42, 1.54), respectively. Energy resolution is 9.76%(137Cs). The energy spectrums show good energy linearity. Only 5000 counts can give good positioning accuracy. The system can clearly separate two 99mTc point source at angle distance of 20°. In this study, we developed the 4π view radiation imaging system, which can be used in real practical applications. The system has good positioning and energy performance. The preliminary test shows that the system also has good potential in low count and two point sources imaging.