Investigation of some radiation attenuation properties of biomedical magnesium alloys: a simulation-based study

Abstract

The utilization of biomedical magnesium alloys has exhibited a notable surge in recent years, attributable to their advantageous biocompatibility, biodegradability, low density, and mechanical properties that are analogous to those of human bone. Despite their low density, typically around 1.74 g/cm3, the radiation transmittance of these materials must be carefully evaluated for applications involving ionizing radiation, particularly in diagnostic and therapeutic medical devices. The objective of this study is to theoretically investigate the gamma-ray and charged particle interaction properties of four commercially available biomedical magnesium alloys: LA141, AZ31B, AZ91D, and WE43A. To this end, a combination of simulation tools was employed, including GAMOS (Geant4-based Architecture for Medicine-Oriented Simulations), Phy-X/PSD, SRIM (Stopping and Range of Ions in Matter), and NIST databases such as XCOM and ESTAR. The parameters of radiation shielding, including the mean free path (mfp), the half-value layer (HVL), the mass attenuation coefficient (MAC), and the linear attenuation coefficient (LAC), were evaluated within the energy range of 81-1408 keV. Among the alloys, WE43A demonstrated the highest linear attenuation coefficient (LAC) at low energies, with a maximum LAC of 0.736 cm-1 at 81 keV. In contrast, LA141 exhibited the lowest LAC of 0.070 cm-1 at 1408 keV. The HVL values, which indicate the thickness required to reduce the incident gamma-ray intensity by half, ranged from approximately 7.2 to 9.8 cm. This increase with photon energy was expected, due to reduced photon interaction probabilities at higher energies. The minimum mfp at 662 keV was observed for WE43A (7.069 cm), while the maximum was recorded for LA141 (9.843 cm). This finding underscores the pivotal role of alloy density in determining photon interactions. Furthermore, the interactions of charged particles were analyzed through electron stopping power and CSDA (Continuous Slowing Down Approximation) range calculations. The analysis of stopping power demonstrated that electron energy loss was significantly influenced by material density and composition. WE43A, which demonstrated the highest density (1.84 g/cm3), exhibited the highest total stopping power across the examined energy spectrum (0.01-10 MeV). CSDA range values demonstrated the exponential increase in electron path length with increasing kinetic energy, with WE43A again showing shorter ranges compared to lighter alloys, affirming its potential for controlled energy deposition. Furthermore, the use of SRIM simulations to study the penetration of H+, He2+, O2-, and Au+ ions also reflected density-dependent trends. At 10 MeV, the Au ion range was 3.56 mu m in WE43A and 3.89 mu m in the less dense LA141. The He2+ and H+ ions exhibited increased penetration depths, measuring 105.24 and 114.03 mu m, respectively. This phenomenon can be attributed to their reduced size and mass, which leads to a reduced number of interactions per unit path length. In conclusion, the study underscores the radiation attenuation potential of Mg alloys, particularly WE43A, for enhancing contrast in X-ray imaging and providing effective shielding in radiological procedures. The adjustable radiation interaction characteristics of these materials, in conjunction with their superior biocompatibility, position them as strong candidates for utilization in next generation biomedical implants and radioprotective applications.