Effective shielding elements and oxides for medical X-ray applications

This study explores the potential of elements with atomic numbers 55-83 and their prevalent oxides as substitutes for lead in X-ray shielding applications, focusing on reducing mass and thickness while maintaining effectiveness across energies from 10 keV to 500 keV. The Pb-equivalent mass and thickness ratios were calculated for these elements and oxides, revealing significant variations in attenuation properties. To demonstrate the differences between broad-beam and narrow-beam attenuation as well as between mono-energetic photons and X-ray tube-generated spectra, measurements and calculations for 0.5 mm Pb were compared. Ta and W, as well as Pb and Bi oxides, are suitable substitutes at 15 keV, making them ideal for mammography. Sm, Nd, and Bi, as well as several oxides, are advisable alternatives near 50 keV, making them suitable for dental X-ray shielding. Pb and Bi oxides are preferred for CT applications, along with others, whereas Bi and W are appropriate for high-energy X-rays. The study also reveals that at low photon energies, PbO, Pb₃O₄, PbO₂, and Bi₂O₃ demonstrate optimal Pb-equivalent ratios slightly above unity. Alternatives such as WO₂ and YbO exhibit potential at elevated energies. Calculations performed using X-ray tube spectra generated at varying X-ray tube voltages indicated that PbO outperforms other oxides at lower tube voltages, while YbO excels at energies greater than its K-edge. These findings provide valuable insights for the development of Pb-free X-ray shielding solutions that can meet the demands of various medical imaging modalities, enhancing safety and efficiency.