Radiation and Environmental Biophysics最新文献

Radon gas, a significant source of indoor radiation exposure, poses serious health risks, particularly lung cancer. This study employs Computational Fluid Dynamics (CFD) using the ANSYS Fluent software to model the behaviour and distribution of radon gas in a laboratory space equipped with granite countertops. A three-dimensional model of the laboratory, including its geometry, ventilation rates, and radon exhalation sources, was developed to simulate radon concentrations, particularly at breathing height. Radon exhalation rate from the granite and other surfaces in the room was measured experimentally. Numerical results, validated by experimental measurements, revealed a 30% increase in average radon concentration following the installation of granite countertops with an exhalation rate of 6.5 Bq m^-2 h^-1. The spatial distribution of radon, particularly near the countertops, indicated regions where radon accumulated at concentrations exceeding the action threshold of the US Environmental Protection Agency of 148 Bq/m³. Additionally, while natural ventilation effectively reduced overall radon levels, its efficiency was diminished near the countertops due to complex airflow patterns, leading to radon accumulation in breathing zones. This study demonstrates the ability of numerical methods to identify centers of radon gas accumulation by predicting airflow patterns and behaviours at various ventilation rates, emphasizing the need for effective ventilation strategies, such as localized exhaust systems, to reduce radon exposure in critical areas.

Although previous studies already reported on backscatter and depth dose correction factors for a Polymethyl-methacrylate (PMMA) phantom to determine the operational quantity [Formula: see text], more comprehensive evaluations for a wider range of tissue-equivalent phantoms are limited. Besides addressing this gap, the present study also provides phantom scatter correction factors for various phantoms. Correction factors were calculated to determine the [Formula: see text] in solid phantoms (PMMA, Polystyrene, Solid Water, Plastic Water, Virtual Water, RW3, WE210, and A150) and the International Organisation for Standardisation (ISO)-recommended PMMA-walled water phantom involving detector materials such as air, LiF and Li₂B₄O₇ for ISO reference photon beams (N40, N80, N100, N150, N200, N250 x-rays and 662 keV gamma photon). The calculations were performed using the EGSnrc-based Monte Carlo code system. These correction factors include backscatter factor, depth dose factor and phantom scatter, for photon beams with normal incidence on the phantom. The calculated values of the backscatter and depth dose factors are in good agreement with published values for a PMMA phantom. The values of backscatter factor calculated in solid phantoms such as A150, Solid Water, Plastic Water, Virtual Water and WE210 were similar to those calculated in tissue phantom. The phantoms PMMA, Polystyrene and RW3 showed higher backscatter factor values in the energy range N40 - N100 as compared to the tissue phantom. The depth dose factors were comparable in all phantoms except in Polystyrene in which they were higher for N40 photons. The study shows that application of phantom scatter correction is important for phantoms such as PMMA (N40- N250), Polystyrene (N40- N150), RW3 (N40 & N80), Solid Water (N40 & N80), Virtual Water (N40 & N80) and WE210 (N40 & N80). A150, Plastic Water and PMMA-walled water phantoms behave like tissue-equivalent phantoms at all photon energies as the phantom scatter correction was in the range of 0.97-1.02, depending upon energy. This study demonstrates the importance of applying phantom scatter correction factors into the calculation of [Formula: see text], particularly for low-energy photon beams.

The research described in this paper aimed to identify ²²²Rn concentrations in the serum of healthy individuals and lung cancer patients. Additionally, CBC parameters such as WBC (White Blood Cell count), RBC (Red Blood Cells), MCH (Mean Corpuscular Hemoglobin), and PLT (Platelets) were measured and their correlation with the corresponding ²²²Rn concentrations in the serum of the lung cancer patients was investigated. ²²²Rn concentrations in serum samples were measured using a CR-39 detector. The mean ²²²Rn concentration in the serum of the patients was 22.62 ± 3.85 Bq/m³, while that in serum of the healthy individuals was 2.72 ± 0.71 Bq/m³. Also, it was found that the mean WBC, RBC, MCH, and PLT levels in the serum of the patients were 7.15 ± 0.58 cells/L, 4.24 ± 0.17 cells/L, 29.23 ± 0.60 pg, and 285.52 ± 21.78 cells/L, respectively. The results revealed statistically significant differences in ²²²Rn concentrations when comparing the samples of the patients with those of the healthy individuals. In addition, a reasonable correlation was found (p < 0.01) between the ²²²Rn concentrations and MCH levels in serum of the patients. It is concluded that, given the observed correlations, further studies are necessary to investigate whether there is any causal relationship behind the observed correlations.

This study investigates the radiation shielding performance of lead borosilicate waste glass when incorporated as an additive into cement-bitumen composites. The utilization of lead borosilicate glass, a byproduct of industrial processes, offers a dual advantage: it enhances the gamma-ray attenuation capacity of the composite achieving a mass attenuation coefficient of 7.85 × 10⁻² cm²/g and simultaneously contributes to the sustainable management of radioactive waste by improving the compressive strength to 32.9 MPa. Cement-bitumen mixtures were prepared with varying concentrations of the waste glass and evaluated through both experimental measurements and theoretical modeling. The linear attenuation coefficients demonstrated a marked improvement in shielding efficiency with increasing lead content. Computational tools, including XCOM and Geant4, were employed to simulate photon interactions and validate the experimental findings. The simulation results were in strong agreement with experimental data, confirming the enhanced attenuation properties at higher glass concentrations. These findings suggest that lead borosilicate waste glass is a promising additive for improving the gamma radiation shielding properties of cement-bitumen matrices, with potential applications in nuclear waste immobilization and radiation protection. Furthermore, the approach promotes sustainable recycling of industrial waste, aligning with environmental conservation goals. Further research is recommended to optimize glass loading and assess the long-term durability and structural performance under diverse environmental conditions.

The two-parametric Avrami-Dobrzyński model, originally based on the condensed matter physics for phase transitions, was applied to the cumulative populational mammary cancer data of laboratory rats. The joint effect of parity, irradiation and BRCA1 mutation on breast cancer incidence was analysed. The study showed that the proposed model fits well with the data points, however, the values of parameters differ regarding the investigated group of animals. It was concluded that both model's parameters, which relate to the dimension of carcinogenesis dynamics and the age distribution, are good candidates for cancer risk assessment regarding different risk factors.

External radiotherapy combined with internal radiotherapy in cervical cancer can provide a boost to the target volume to increase tumour control. At the same time internal radiotherapy protects neighboring organs. The aim of the present study was to dosimetrically compare three external beam radiotherapy techniques each combined with internal radiotherapy to evaluate the combination that offers the best organ protection. Treatment plans of 20 cervical cancer patients were created for external (including three-dimensional conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT)) as well as brachytherapy. The prescribed dose was 50 Gy in 25 fractions for external and 21 Gy in three fractions for internal radiotherapy. The following organs at risk (OARs) were evaluated: bladder, rectum, sigmoid and bowel bag. The study analyzed the results of different treatment combinations in terms of dosimetric values for various parameters. The D₉₀ for the clinical target volume was around 120 Gy, with the highest value seen in 3D-CRT + BT (brachytherapy) combination at 120.59 Gy. For the bladder, the D_2cc remained below the recommended threshold of 90 Gy, with the lowest value obtained for the BT + IMRT combination at 79.2 Gy. For the rectum, both D_2cc and D_1cc remained below the recommended threshold of 75 Gy for both parameters. All techniques fell below the recommended dose of 75 Gy for the sigmoid. For the intestine, there were statistically significant differences between BT + IMRT and BT + 3D-CRT. The VMAT technique showed superiority over IMRT in tumour volume coverage and several organ-at-risk parameters. Generally, intensity-modulated techniques showed dosimetric advantage over the traditional 3D technique in cervical cancer. In addition to providing better compliance and homogeneity, they provided superior protection for organs at risk, especially for bowel bag. It is concluded that the BT + IMRT technique provided the best protection for organs at risk based on the lowest OAR dosimetric values, especially for the intestine.

While numerous studies have investigated the impact of various nanoparticles (NPs) in polymer matrices for radiation shielding, there is a notable gap in the literature regarding a comprehensive examination of both individual and combined selected NPs with functional polymers. This study aims to address this gap by systematically evaluating the synergistic potential of multiple high-Z NPs and specialized polymer matrices in radiation shielding design, particularly for computed tomography (CT) applications. A single and mixture range of NPs, including Gd₂O₃, Sm₂O₃, CeO₂, HfO₂, IrO₂, Bi₂O₃, and WO₃, were combined with polymers such as chlorinated polyvinyl chloride (CPVC), polychlorostyrene (PCS), polytrifluorochloroethylene (PTFCE), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), and polyvinylidene chloride (PVDC) which served as matrices. By means of Geant4 Monte Carlo simulations, the study assessed the shielding effectiveness of these nanocomposites at various X-ray energies (80, 100, 120, and 140 kVp). The results revealed that nanocomposites containing Sm₂O₃ and Gd₂O₃ exhibited superior X-ray attenuation at 80 and 100 kVp, while the HfO₂ nanocomposite demonstrated enhanced shielding at 120 and 140 kVp. Additionally, multi-filler nanocomposites with 30 wt% of Sm₂O₃ + HfO₂ (SmHf) and Gd₂O₃ + Bi₂O₃ (GdBi) exhibited improved performance at 80 and 140 kVp, respectively. Notably, the 30 wt% Gd₂O₃ + IrO₂ (GdIr) multi-filler nanocomposite outperformed others at 100 and 120 kVp. It is concluded that a combination of NPs with K-edge values close to the mean energy of the investigated X-ray spectra provide better shielding capabilities than single NPs, highlighting their potential for applications in radiation protection.

Birds are bioindicators of anthropogenic environmental stress, including the changes caused by radioactive contamination of ecosystems. Any radiation-induced biological effects can be the consequence of exposure both after hatching and during the embryonic period. Therefore, it is necessary to quantify radiation doses to the embryo when interpreting observed radiobiological effects in birds. This is especially true for areas contaminated with Ca-like ⁹⁰Sr. The levels of radionuclide accumulation in the eggshell can be extremely high, which leads to chronic embryo exposure. Consequently, the objective of the present study was to develop a method to calculate the dose to a herring gull embryo exposed to ⁹⁰Sr distributed in egg compartments (shell, embryo body, albumen and yolk). To achieve this, the time-dependent Sr distribution in the egg compartments was modeled. Additionally, dosimetric modeling was carried out to obtain dose factors that convert the radionuclide activity in different compartments of an egg to embryo dose at various stages of embryogenesis. It has been shown that the accumulated dose to the herring gull embryo can be calculated based on ⁹⁰Sr total activity in the egg using a dose conversion factor of 0.44 μGy Bq^-1. Since the eggshell contains more than 90% of total ⁹⁰Sr activity, the conversion from eggshell activity to embryo dose would be practically the same as that from the total egg activity - 0.46 μGy Bq^-1. The main dose fraction (~ 99%) accumulates at the last stage of embryogenesis (from 13 to 26 days). The proposed method allows for an estimation of individual radiation doses to embryos based on eggshell radiometry. This creates a new opportunity to study how dangerous any radiation exposure of birds could be during the embryonic period.