Monte Carlo evaluation of the attenuation effects of bismuth, lead and alternative composite materials used in radiation protection

Objective: In some diagnostic examinations, area of interest not only includes target organs but also radiation sensitive organs which are unnecessarily irradiated. There are adverse opinions like high cost and lack of practicality in use regarding Bismuth (Bi) shielding materials which are used on patients to decrease radiation damage and probable risk of cancer as a result of exposure to radiaton. On the other hand, for Lead (Pb) shielding materials which are used for the protection of radiation workers, there are several disadvantages due to high weight and toxicity of the material making them not preferable. This study which has its base focused on the deficiencies defined above, aims to use Monte Carlo (MC) simulation software for the evaluation of the attenuation effects of some elements and composite materials created by the software in order to develop new shielding materials. Material and Method: MC based GAMOS simulation program has been used in compliance with the diagnostic energy range to examine the differences between energy dependent mass attenuation coefficients of some metals and lanthanides, as well as the amount of dose reduction due to shielding thickness. Following the verification of the obtained results with the mass attenuation values offered in the NIST (National Institute of Standards and Technology) database (error<3%), 20 different samples have been composed according to the determination of variable percentage abundances of elements. Properties like K shell binding energy, atomic number, density, toxicity have been considered in the selection of elements. Results: The best 10 composite samples out of 20 have been selected and compared to bismuth and lead. For most of the samples, higher mass attenuation coefficients have been obtained compared to bismuth and lead, between the energy ranges of 50-90 keV and 50-80 keV respectively. Conclusion: Energy dependent mass attenuation properties of composed samples have been compared to those of bismuth and lead by means of simulated workspace, and the most successful samples have been determined. The most successful ones have been Sample 3 (Europium, Dysporsium, Barium, Bismuth), sample 8 (Ytterbium, Erbium, Europium, Bismuth) and sample 9 (Ytterbium, Erbium, Antimony, Bismuth). Keywords : Monte Carlo Calculations, Radiation Protection, X-Ray