Omnidirectional 3D Gamma-ray Imaging with a Free-moving Spherical Active Coded Aperture

The integration of gamma-ray imaging and visual scene data in 3D has been shown to improve radioactive source localization and mapping capabilities. Contextual sensors such as visual cameras and light detection and ranging units are used with Simultaneous Localization and Mapping algorithms to create 3D scene models and to track both the position and orientation of the system in real-time as it moves freely through an environment. The 3D scene models are also used to constrain the gamma-ray image reconstruction to only occupied voxels in the 3D space, increasing localization accuracy and decreasing computational time. These concepts have recently been demonstrated with mobile germanium and CdZnTe (CZT) Compton imaging systems. Here we utilize a hand-portable, CZT-based, free-moving spherical active coded aperture system currently being developed at Lawrence Berkeley National Laboratory. The active configuration enables broad-energy dual-mode coded aperture and Compton imaging, and the spherical arrangement of detectors overcomes the limited field-of-view inherent in active two-plane systems. In this work, we demonstrate the omnidirectional 2D and 3D imaging capability of the system in the low-energy coded aperture modality and explore GPUparallelization for real-time reconstruction.