Coded aperture and Compton imaging capability of spherical detector system design based on GAGG scintillators: A Monte Carlo study

In the study of this paper, based on the symmetry of regular icosahedron, a spherical detector system for 4 pi field-of-view (FOV) gamma imaging was proposed based on 80 GAGG (Ce:GAGG, Gd3Al2Ga3O12) scintillator pixels. The spherical detector system combines both coded aperture (CA) and Compton imaging (CI) modalities. The detector system was simulated precisely with an experimental test of one representative GAGG pixel. Several radionuclides with characteristic energy ranging from 59.5 keV to 1.33 MeV were imaged under the far-field situation. Both imaging modes realize the 4 pi view while the coded aperture method achieves a higher image quality for radioactive sources with lower energy and the Compton method performs conversely. The imaging system can localize a 10 mCi Cs-137 point source at 10 m within 1 s in the two modes and the Compton imaging mode reaches a high detection efficiency of up to 200 cps/mu Sv/h for Cs-137. And the angular estimation full-width-at-half-maximum (FWHM) was approximately 5.2 degrees for coded aperture mode and 14 degrees for Compton mode. The angular resolution was evaluated to be better than 30 degrees. The high intrinsic imaging sensitivity and reasonable imaging quality make this detector system design attractive for far-field radiation imaging.