Radiation shielding assessment for interventional radiology personnel: Geant4 dosimetry of lead-free compositions.

The inherent biological hazards associated with ionizing radiation necessitate the implementation of effective shielding measures, particularly in medical applications. Interventional radiology, in particular, poses a unique challenge as it often exposes medical personnel to prolonged periods of high x-ray doses. Historically, lead and lead-based compounds have been the primary materials employed for shielding against photons. However, the drawbacks of lead, including its substantial weight causing personnel's inflexibility and its toxicity, have raised concerns regarding its long-term impact on both human health and the environment. Barium tantalate has emerged as a promising alternative, due to its unique attenuation properties against low-energy x-rays, specifically targeting the weak absorption area of lead. In the present study, we employ the Geant4 Monte Carlo simulation tool to investigate various formulations of barium tantalate doped with rare earth elements. The aim is to identify the optimal composition for shielding x-rays in the context of interventional radiology. To achieve this, we employ a reference x-ray spectrum typical of interventional radiology procedures, with energies extending up to 90 keV, within a carefully designed simulation setup. Our primary performance indicator is the reduction in air kerma transmission. Furthermore, we assess the absorbed doses to critical organs at risk within a standard human body phantom protected by the shield. Our results demonstrate that specific concentrations of the examined rare earth impurities can enhance the shielding performance of barium tantalate. To mitigate x-ray exposure in interventional radiology, our analysis reveals that the most effective shielding performance is achieved when using barium tantalate compositions containing 15% Erbium or 10% Samarium by weight. These findings suggest the possibility of developing lead-free shielding solutions or apron for interventional radiology personnel, offering a remarkable reduction in weight (exceeding 30%) while maintaining shielding performance at levels comparable to traditional lead-based materials.

Gamma-irradiation applied to the synthesis of the nanocrystalline Gd2O2S:Pr powders for imaging applications.

Nanocrystalline Gd2O2S:Pr powders were successfully synthesized by the co-participation method. The changes of size, shape and luminescence properties of these nanocrystalline powders were studied under different gamma doses (0-50 kGy) during the synthesizing process. Also, the structural, morphology and luminescence properties of these nanocrystalline powders were characterized using the X-ray diffraction, field emission scanning electron microscopy, energy dispersion of X-ray spectroscopy, photoluminescence, and thermoluminescence. The XRD results confirmed that the nanocrystalline Gd2O2S:Pr powders have a pure hexagonal structure with the high crystallinity at a temperature of 900 °C, and the gamma radiation doses have no effect on the structure. The SEM images showed that the nanocrystalline Gd2O2S:Pr powders have a spherical shape and are agglomerated when the irradiation dose increases. These nanopowders, which were prepared at an irradiation dose of 40 kGy, show the lowest crystallite size and hence the highest intensity of emission peaks at the wavelengths of 506, 515 and 671 nm, which are corresponded to the transitions of the 3P1-3H4, 3P0-3H4 and 3P0-3F2 of Pr ions, respectively. The X-ray radiography image was obtained by the screen of Gd2O2S:Pr nanopowders (prepared at 40 kGy gamma dose), coupled with a radiographic film. The TL glow curves of the sample, prepared at 40 kGy gamma dose, were recorded under the X-ray irradiation in the times of 5 and 10 min. The heating rate and preheat temperature were obtained 2 and 50 °C, respectively. The obtained results were investigated in details.

Selective removal of uranium ions from contaminated waters using modified-X nanozeolite.

In order to efficiently remove of uranium anionic species (which are the most dominant species of uranium in natural water at neutral pH) from contaminated waters, nano-NaX zeolite was synthesized and then modified using various divalent cations (Mg2+, Ca2+, Mn2+) and ZnO nanoparticles (from 1.7 to 10.3wt%). Different characterization techniques of XRF, XRD, FE-SEM, TEM, FT-IR, and AAS were used to characterize the final synthesized absorbents. Sorption experiments by batch technique were done to study the effect of solid-liquid ratio, initial uranium concentration, contact time and temperature under neutral condition of pH and presence of all anions and cations which are available in the waters. Results showed that although nano-NaX zeolite due to its negative framework charge had a low sorption capacity for adsorption of uranium anionic species, but modification of parent nano-NaX zeolite with ZnO nanoparticles and various cations effectively improved its uranium adsorption capacity. Also, results showed that under optimum condition of pH=7.56, contact time of 60min at 27°C with solid-liquid ratio of 20g/L a maximum uranium removal efficiency of 99.7% can be obtained in the presence of all anions and cations which are available in the drinking waters by NaX/ZnO nanocomposite.

Evaluation of HPGe detector efficiency for point sources using virtual point detector model.

The concept of a virtual point detector (VPD) has been developed and validated in the past for Ge(Li) and HPGe detectors. In the present research, a new semi-empirical equation involving photon energy and source-virtual point detector distance for the efficiency of point sources by HPGe detectors is introduced , which is based on the VPD model. The calculated efficiencies for both coaxial and off-axis geometries by this equation are in good agreement with experimental data. The estimated uncertainties are less than 4%.