Document Type : Original Paper
Ray Medical Engineering Department, School of Mechanical Engineering, Shiraz University, Shiraz Iran
Radiation Research Center, School of Mechanical Engineering, Shiraz University, Shiraz, Iran
Lead-based shields are the most widely used attenuators in X-ray and gamma ray fields. The heavy weight, toxicity and corrosion of lead have led researchers towards the development of non-lead shields.
Materials and Methods
The purpose of this study was to design multi-layered shields for protection against X-rays and gamma rays in diagnostic radiology and nuclear medicine. In this study, cubic slabs composed of several materials with high atomic numbers, i.e., lead, barium, bismuth, gadolinium, tin and tungsten, were simulated, using MCNP5 Monte Carlo code. Cubic slabs (30×30×0.05 cm3) were simulated at a 50 cm distance from the point photon source. The X-ray spectra of 80 kVp and 120 kVp were obtained, using IPEM Report 78. The photon flux following the use of each shield was obtained inside cubic tally cells (1×1×0.5 cm3) at a 5 cm distance from the shields. The photon attenuation properties of multi-layered shields (i.e., two, three, four and five layers), composed of non-lead radiation materials, were also obtained via Monte Carlo simulations.
Among different shield designs proposed in this study, the three-layered shield, composed of tungsten, bismuth and gadolinium, showed the most significant attenuation properties in radiology, with acceptable shielding at 140 keV energy in nuclear medicine.
According to the results, materials with k-edges equal to energies common to diagnostic radiology can be proper substitutes for lead shields.