Impact of ¹⁸ F-FDG Vials on Well Counter Background Radiation: Evaluating Shielding and Distance Effects

¹⁸F-FDG, widely used in PET imaging, produces high-energy 511-keV annihilation photons that pose radiation exposure risks in radiopharmaceutical preparation and handling areas, or hot labs. Understanding how environmental factors influence background radiation in hot labs is essential for maintaining a safe workflow and ensuring accurate instrument readings. This study aims to evaluate the impact of shielding and distance on background radiation levels detected by a well counter in the presence of ¹⁸F-FDG vials. Eight ¹⁸F-FDG vials were measured in a specific sequence under 7 conditions. First, a background measurement was taken with no vial present. This was followed by measurements with the vials placed at distances of 1, 2, and 3 m from the detector, each tested both with and without the standard tungsten shielding. Count rates (counts per minute [cpm]) were recorded and analyzed for each condition. Unshielded ¹⁸F-FDG values (21,157 cpm at 1 m, 2,166.4 cpm at 2 m, and 1,582.9 cpm at 3 m) were significantly higher than those for shielded ¹⁸F-FDG at all distances (529.4, 243.5, and 229.4 cpm at 1, 2, and 3 m, respectively). Shielding reduced radiation exposure by up to 97.5% at 1 m. Shielded values at 3 m approached background levels (201.0 cpm), demonstrating the compounded effectiveness of distance and shielding. Both distance and shielding reduced radiation exposure from ¹⁸F-FDG sources, with the greatest shielding benefit observed at closer distances. These findings emphasize the importance of spatial and protective strategies in hot lab environments to safeguard technologists, maintain regulatory compliance, and ensure precise measurements from radiation detection instruments.