A Wide Energy Range and 4 pi-View Gamma Camera with Interspaced Position-Sensitive Scintillator Array and Embedded Heavy Metal Bars

(1) Background: Gamma cameras have wide applications in industry, including nuclear power plant monitoring, emergency response, and homeland security. The desirable properties of a gamma camera include small weight, good resolution, large field of view (FOV), and wide imageable source energy range. Compton cameras can have a 4 pi FOV but have limited sensitivity at low energy. Coded-aperture gamma cameras are operatable at a wide photon energy range but typically have a limited FOV and increased weight due to the thick heavy metal collimators and shielding. In our lab, we previously proposed a 4 pi-view gamma imaging approach with a 3D position-sensitive detector, with which each detector element acts as the collimator for other detector elements. We presented promising imaging performance for Tc-99m, F-18, and Cs-137 sources. However, the imaging performance for middle- and high-energy sources requires further improvement. (2) Methods: In this study, we present a new gamma camera design to achieve satisfactory imaging performance in a wide gamma energy range. The proposed gamma camera consists of interspaced bar-shaped GAGG (Ce) crystals and tungsten absorbers. The metal bars enhance collimation for high-energy gamma photons without sacrificing the FOV. We assembled a gamma camera prototype and conducted experiments to evaluate the gamma camera's performance for imaging Co-57, Cs-137, and Co-60 point sources. (3) Results: Results show that the proposed gamma camera achieves a positioning accuracy of <3 degrees for all gamma energies. It can clearly resolve two Cs-137 point sources with 10 degrees separation, two Co-57 and two Co-60 point sources with 20 degrees separation, as well as a 2 x 3 Cs-137 point-source array with 20 degrees separation. (4) Conclusions: We conclude that the proposed gamma camera design has comprehensive merits, including portability, 4 pi-view FOV, and good angular resolution across a wide energy range. The presented approach has promising potential in nuclear security applications.