(POS-41) Gamma Cameras - A Comparative Study of Energy and Spatial Resolution in Gamma Imaging

Hermann Friedrich – Fraunhofer INT; Theo Köble – Fraunhofer INT; Olaf Schumann – Fraunhofer INT; Thorsten Teuteberg – Fraunhofer INT; Sebastian Chmel – Fraunhofer INT

The detection, identification and classification of radioactive or nuclear material remains of critical importance. Advanced gamma imaging technologies are essential tools for these tasks, offering non-destructive and efficient analysis. This paper presents measurements conducted with H3D’s M420 gamma camera and compares its performance to NUVIA’s NuVISION system, building on the work presented in the previous year, which explored general capabilities and limitations. Both devices use cadmium zinc telluride (CZT) crystals, allowing compact, lightweight, and cooling-free designs. Key differences between the systems include crystal thickness - 6 mm for NuVISION and 10 mm for M420 - which affects efficiency, particularly at higher gamma energies such as those of Co-60 (1173 keV, 1332 keV). The study also includes a comparative evaluation of the gamma spectra and energy resolution across a wide gamma-ray range. Both systems comprise a high resolution capability using a coded mask and a 360° field of view capability using Compton imaging. The focus of the NuVISION lies in high-resolution imaging using a coded mask, while the M420 primarily focuses on Compton imaging. Nuclides covering the whole energy range are used to investigate the differences concerning both imaging types. For Am-241 (59 keV) only coded mask technology is effective due to the absence of Compton scattering. Furthermore, the spatial resolution of both devices is analyzed, providing insights into their ability to accurately localize radioactive sources. Both systems employ tungsten masks, which introduce Kα bremsstrahlung lines into the energy spectrum. The energy is in the same region as the 59 keV line from Am-241, which leads to an incorrect identification of Am-241. The different approaches taken by the manufacturers to address and mitigate this issue, along with their outcomes, are also investigated. To further investigate the Compton imaging possibility, sources are measured within the whole 360° field of view.