Absolute Gamma Source Positioning with Position-sensitive Scintillation Detector Arrays

Radioactive sources are widely used in industrial and medical applications. In home-land security, it is important to monitor radioactive source in public areas such as airport to prevent public hazard. Traditional radiation detection devices such as Geiger counter cannot provide position information. Exist imaging devices including Gamma cameras with mechanical collimators, or Compton cameras can only determine directional information of the radioactive sources over the 4 pi angular space, which is not enough for accurate source positioning in the crowded areas with high population density. In this work, we propose a novel method to achieve 3-D imaging capability of the absolute radioactive sources position with position-sensitive scintillator detector arrays. Targeting at application in a typical public places such as airports, we propose a 6-detector imaging system setup. The detector design is based on a pixilated dual-ended GAGG scintillation detector block that has been developed in our lab. The measured photon count distribution of all the six detectors are combined together to form the projection data. A ML-EM algorithm is used reconstruct the source intensity image in Cartesian coordinates. In Monte Carlo simulation, a 511 keV point source was placed at four different positions in the FOV to measure the projection data. Both the positioning accuracy and the FWHM image resolution were calculated from the reconstructed image to evaluate the performance of the proposed imaging method. The reconstructed images converge to desired point-type distribution with certain spread observed in both the simulation and the experimental study. Accurate positioning accuracy is achievable in all cases. In conclusion, the proposed method demonstrates feasibility for absolute positioning of the radioactive sources in 3-D Cartesian space. We believe that it is promisingly useful in public safety applications.