Rotating Scatter Mask for Gamma Source Imaging

Julie V. Logan

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Current gamma imaging systems are limited in utility due to their cost, size, narrow field of view, and low image formation efficiency. This effort constitutes a critical step in the development of an imaging system that is limited by none of these factors. This gamma imaging system consists of a routine NaI(Tl) scintillation detector coupled with a rotating scatter mask, the geometry of which is specifically chosen such that the detected signal obtained from one complete mask rotation provides sufficient information to uniquely determine the source direction. This mask encases the detector and can be completely encapsulated within a 0.045 m3 cube (side length of 35.56 cm). A GEANT4 simulation was developed to model the functionality of this system and obtain a library of detector response curves. This simulation was validated via statistical comparisons with experimental and MCNP data. Using the results of the simulation, an algorithm was developed that was shown to predict experimental source direction over a nearly 4π field of view with average errors that were smaller than the resolution in the library of curves employed to image, with an average error in both the azimuthal angle θ and polar angle φ of less than 5°.