Energy-specific attenuation and half-value layers of BaSO₄-loaded rubber for Lu-177 gamma-ray shielding

With the expanding use of lutetium-177 (Lu-177) radiopharmaceutical therapy, reducing occupational radiation exposure has become increasingly important. Conventional bedside shielding mainly relies on lead, which is heavy and difficult to handle. This study evaluated the gamma-ray shielding performance of lightweight and flexible barium sulfate (BaSO₄)-loaded rubber.

BaSO₄-loaded rubber (density, 2.3 g/cm³) was fabricated with nominal thicknesses of 5, 8, 10, 13, and 15 mm; pieces were also stacked to achieve thicknesses of 20, 30, and 51 mm. Energy spectra of a Lu-177 source were acquired using a SPECT/CT system. Attenuation rates at the 113- and 208-keV photopeaks were measured, and half-value layers (HVLs) were determined by exponential fitting.

Attenuation of both the 113- and 208-keV photopeaks increased with increasing rubber thickness. Scatter radiation around 55 keV was almost completely eliminated by 5-8 mm of shielding. At a thickness of 5 mm, attenuation rates were 51.5% for the 113-keV photopeak and 21.5% for the 208-keV photopeak, increasing to 95.0% and 89.1%, respectively, at 51 mm. Exponential fitting yielded HVLs of 5.0 mm for the 113-keV photopeak and 14.7 mm for the 208-keV photopeak.

BaSO₄-loaded rubber provided effective shielding against Lu-177 gamma rays, particularly at 113 keV. Owing to its light weight, flexibility, and cost-effectiveness, it represents a promising alternative to conventional shielding materials. The energy-specific attenuation characteristics and HVL data obtained in this study provide useful design information for bedside shielding panels and syringe shielding devices used in Lu-177 therapy.