New opportunities in the design of gamma-camera collimators for medical imaging

In nuclear medicine, the gamma camera is one of the more used imaging devices for radionuclide imaging. Gamma camera provide an image of the target organ, with high spatial resolution and sensitivity; gamma cameras use collimators. This paper presents a simple and customizable collimator to be used in radionuclide imaging for preclinical studies, using additive manufacturing (AM) techniques. A numerical analysis, based on GATE Monte Carlo toolkit (vGate 8.2), has been conducted to simulate different configurations of an already working collimator used as reference. In addition to the standard collimator geometry with alternatives materials, we also propose a new concept of collimator to be easily 3D printed, using different 3D printing technologies. We have simulated collimators with square apertures of 1.5 mm and septa of 0.4 mm of thickness, source was Tc99m. The materials simulated were standard tungsten, a PLA doped with tungsten (Rapid 3D Shield Tungsten Filament - Virtual Foundry), a classical PLA filament and P A2200 for the new concept. The results show a similar behavior for what concern the spatial resolution, while for the sensitivity a reduction of about 45% of entries is reported. This is due mainly since the extruded pixel, made of PLA or PA2200, have higher density $(\approx$ 1.24 g/cm^3 for PLA and $\approx 0,95$ g/cm^3 for PA2200) with respect to air $(\approx$ 0,0012 g/cm^J). Further studies are necessary to explore optimization of the used design to reduce the impact of material density.