Radiation and Environmental Biophysics最新文献

The first regional survey of concurrent indoor radon and thoron measurements in Southwestern Nigeria was organized using the passive radon-thoron discriminative detectors RADUET. The measurements were carried out in various dwellings and workplaces across three geological formations within the Southwestern Nigeria basin, which consists of recent sediments in Akoka (Lagos State), cretaceous sediments known as Abeokuta formation in Ilishan (Ogun State), and basements in Alabata (Abeokuta, Ogun State). Both radon and thoron concentrations at 193 sites showed log-normal distributions, with significantly (p < 0.05) higher values of thoron than radon concentrations and a weak correlation (R = 0.224) between the two. The ranges and arithmetic means of the concentrations were 6-132 Bq m^-3and 24 ± 21 Bq m^-3for radon and 2-709 Bq m^-3 and 94 ± 124 Bq m^-3 for thoron, respectively. ANOVA results showed significant variations in radon and thoron concentrations according to the underlying geology, with radon concentrations in Ilishan (cretaceous sedimentary) significantly (p < 0.05) higher than those of Akoka (recent sedimentary) and Alabata (basement complex). No significant differences (p = 0.09) were found between thoron concentrations in Alabata and Ilishan, and both locations had significantly higher (p < 0.05) concentrations of thoron than those recorded in Akoka. A test of the influence of building types showed that radon and thoron concentrations in offices were significantly (p < 0.05) lower than those in homes. None of the thoron concentrations were zero, and almost all were higher than the corresponding radon concentrations. Some of the radon concentrations exceeded the recommended reference level of 100 Bq m^-3, but all were below the action level of 300 Bq m^-3. This study has shown that with high concentrations of thoron, its contributions should not be neglected in indoor radon measurements, particularly in the areas with old sedimentary and basement complex geology. It is noted that dose evaluation is required to quantify the relative contributions of radon and thoron to human exposures in the three locations. Meanwhile, occupants of buildings in the study areas should be encouraged to optimize indoor ventilation.

The measurement of 24-hour urine samples is one of the methods of routine monitoring of intakes of radionuclides. It is briefly mentioned in relevant documents by the International Commission on Radiological Protection that for ¹³¹I the strong decrease of the excretion within the first days after an intake makes the dose calculation from urine measurements unreliable when the time pattern of the intake is unknown. This can result in a major overestimation of the committed effective dose. For quantifying the influence of the time pattern of an intake on the dose, the results of the dose calculation for an acute intake at the midpoint of a monitoring interval (standard assumption) were compared with those for a chronic intake with varying daily activity. For ¹³¹I, aerosols type F, the standard assumption of an acute intake can lead to an overestimation of the calculated dose by a factor of 140 on average as compared to a chronic intake. Among other investigated radionuclides, the strongest overestimation was found for ¹⁴C, gas/vapour type F, when measured every 180 days (factor of 330), although this method complies with current criteria from the international standard ISO 20553. It is recommended that ISO 20553 is supplemented with a criterion that describes the reliability of a monitoring method under different time patterns of an intake additional to the existing criteria. This criterion should set an upper limit for the ratio of the dose calculations under the described assumptions.

The cumulative exposure to X-ray radiation during cardiac intervention can indeed pose various health risks. The present meta-analysis aims to compare novel radiation protective systems (drapes and X-ray shields) versus conventional safety measures on the operator's procedural radiation exposure during cardiac interventions. A systematic review and meta-analysis were performed including randomized controlled trials from PubMed, Embase, Cochrane, Scopus, and WOS until February 2024. The random-effects model was used to report continuous outcomes using mean difference (MD) with a 95% confidence interval (CI). Sixteen Trials with 3,370 patients were included. Novel radiation protective systems were significantly associated with low total operator radiation dose (MD: -7.3, 95%CI [-11.9, -2.7], p < 0.01) with no significant difference between both arms regarding chest radiation dose (MD: -20.7, 95%CI [-48.9, 7.6], p = 0.15) and thyroid radiation dose (MD: -15.4, 95%CI [-32.4, 1.7], p = 0.08). Also, the novel systems were significantly associated with low air kerma (MD: -46.4, 95%CI [-87.3, 5.5], p = 0.03) and low fluoroscopy duration (MD: -0.3, 95%CI [-0.6, -0.04], p = 0.02). However, there was no difference between both arms regarding the total procedure time (MD: -0.7, 95%CI [-3.1, 1.6], p = 0.54), contrast volume (MD: -3.2, 95%CI [-10.2, 3.7], p = 0.36), and dose area product (MD: 628.4, 95% CI [-3,466.9, 4,723.8], p = 0.76). Also, no differences were found between the drape and shields subgroups in most outcomes. The present literature review showed a low to very low certainty level that novel radiation protective systems significantly reduced the total radiation dose exposure of operators and air kerma. They were also associated with lower fluoroscopy duration, insignificantly lower procedure time, and contrast volume. Given the limited available data it is concluded that novel radiation protective systems are promising, but further large-scale, multicenter, placebo-controlled randomized trials are needed to confirm the efficacy of the newly developed RPSs in lowering radiation exposure of staff in the medical setting.

Boron neutron capture therapy (BNCT) is a progressive medical technique that combines the use of boron compounds and neutron radiation to preferentially destroy cancer cells while minimizing, but not entirely eliminating, damage to surrounding healthy tissues. This therapy relies on ¹⁰B, delivered via specific compounds, capturing neutrons and undergoing a nuclear reaction. This capture leads to the emission of high-energy alpha particles and lithium ions, which selectively damage the boron-loaded tumour cells, ultimately leading to their destruction. The key advantage of BNCT lies in its ability to deliver a highly localized and targeted treatment to cancer cells, and sparing healthy tissues from significant radiation damage due to the extremely short range of the reaction products. This makes it particularly suitable for treating certain types of tumours located in sensitive or critical areas where conventional radiation therapy is less effective or poses higher risks. In BNCT, the neutron source is a crucial component of the treatment process. Reactors and accelerators have traditionally been used as neutron sources in BNCT, while recent studies have also explored neutron generators. The success of BNCT depends on the development of effective boron delivery agents and optimized neutron sources, with recent advances in both areas expanding its clinical potential for treating challenging tumours. Recent advances in nanotechnology have introduced carbon dots as promising boron nanocarriers for BNCT. These carbon dots offer high biocompatibility and unique optical properties. Additionally, they have the ability to cross the blood-brain barrier, enabling targeted brain tumour delivery and imaging. Recent progress in molecular biology and imaging technologies is enhancing our knowledge of tumour characteristics and facilitating the development of boron compounds with greater selectivity for cancer cells. The present overview presents the historical development of the two primary BNCT components, the boron compound and neutron source, as well as their potential for future applications.

Radiation protection is a critical pillar supporting the use of nuclear energy and nuclear technologies. The radiation protection system has been established with the accumulation of knowledge and experience. However, it is challenging for an individual or even a committee to master related knowledge and experience comprehensively and meticulously. An intelligent assistant that possesses extensive knowledge and experience in radiation protection is eagerly required. In this work, we propose an intelligent assistant in radiation protection based on a Large Language Model (LLM) with a knowledge base. The assistant can provide reliable answers with references from authoritative publications. The assistant was developed using open-source toolkits and open-source LLMs, and demonstrated satisfying answers to professional queries. Users can obtain reliable answers with references through the web-based user interface (UI). The assistant is designed for local deployment and utilizes private datasets, thereby addressing issues related to privacy and data security. The effectiveness of the assistant was evaluated by comparing it with LLM applications with web search. The results show that our method with a much smaller number of model parameters can deliver more precise and pertinent responses within the domain of radiation protection than web search-based systems. This work is a preliminary attempt to establish an intelligent assistant in the field of radiation protection, and it shows the potential for using LLM to increase efficiency in radiation protection-related tasks.

Undoubtedly, the precise measurement and determination of the optimum delivered dose to patients during diagnostic and therapeutic procedures is essential. This study estimated the human absorbed dose of the novel GRPR-targeting single-photon emission computed tomography (SPECT) imaging agent [^113mIn]In-RM2 (GRPR - gastrin-releasing peptide receptor) for potential clinical application in diagnosing GRPR-positive tumors, particularly prostate cancer, using animal experimental data and Monte Carlo simulation. The radiolabeled compound was prepared under optimized conditions using an in-house developed ¹¹³Sn/^113mIn generator, with a molar activity at least 43 GBq/µmol. The radiochemical purity of the final product was evaluated using radio-thin layer chromatography (RTLC) and high-performance liquid chromatography (HPLC), revealing a purity > 98%. The complex demonstrated high stability for at least three hours post-incubation. The biodistribution of the radiotracer in mice showed rapid blood clearance, with the primary excretion route being the urinary tract. Additionally, this SPECT agent showed high accumulation in GRPR-expressing organs at various time points. The time-integrated activity of animal source organs was extrapolated to human source organs using a mass-scaling method. Finally, the absorbed dose to human organs was calculated using the MCNPX software (Version 2.6.0) and a voxel-based human phantom developed by Oak Ridge National Laboratory (ORNL). The results showed that the pancreas and kidneys received the highest absorbed doses of 0.008 ± 0.0007 and 0.0036 ± 0.0003 mGy/MBq, respectively, while all other organs received negligible doses. Moreover, this novel SPECT radiotracer exhibited lower absorbed doses in nearly all organs compared to similar radiopharmaceuticals. Overall, [^113mIn]In-RM2 can be considered a safe and promising agent for SPECT imaging.

The choice of a CT-RED calibration curve directly influences the accuracy of dose calculation in treatment planning systems (TPS), depending on treatment technique, anatomical site and calculation algorithm. This study aimed to evaluate the impact of variations in CT-RED calibration curves due to different tube voltages (kVp) on breast cancer treatment plans as a function of calculation algorithm. CT-RED calibration curves were generated using a CIRS M062 phantom scanned with a 16-slice HITACHI Supria CT scanner at 80, 100, 120, and 140 kVp. These curves were applied to treatment plans for left breast cancer using the Collapsed Cone (CC) and X-ray Voxel-based Monte Carlo (XVMC++) algorithms in MONACO TPS (v6.6.2). Dose-volume histograms and dose statistics were analyzed to assess dose metrics for planned target volumes (PTV) and organs at risk (OAR). Monte Carlo-based dose calculations showed significant sensitivity to kVp settings, while CC results exhibited clinically negligible effects, underscoring that the impact of kVp on dose calculation depends on the algorithm used. Thus, to ensure accurate dose calculations, it is important to adjust calibration curves for each kVp setting when using Monte Carlo algorithms. Furthermore, it is recommended to include this adjustment into the CC algorithm, despite the minimal differences observed, in order to ensure consistency with the ALARA (As Low As Reasonably Achievable) principle.

The increased risk of lung cancer from radon progeny among Newfoundland fluorspar miners is well established. In the present study, an internal cohort analysis was conducted to investigate whether radon progeny is also associated with increased mortality from other cancers. Consequently, associations between cumulative radon progeny and cancer mortality (excluding lung cancer) were evaluated in a cohort of 2,110 miners. Mortality was ascertained from 1950 to 2016. Individual-level exposure to radon progeny in working level months (WLM) was determined for each miner during their employment. For cancers with at least ten deaths, Poisson regression was used to estimate excess relative risks (ERRs). Cancer site-specific relative risks were derived for mortality from common cancers within the cohort, specifically: colorectal, prostate, stomach and all cancers (excluding lung cancer). Relative risks were adjusted for age, calendar period, and the number of cigarettes smoked daily determined from smoking surveys. In total, 260 cancer deaths, excluding lung cancer, were identified during follow-up. The relative risk of death from these cancers was 1.26 (95% confidence interval (CI): 0.92, 1.75) among underground miners with a cumulative exposure of ≥ 50 WLM when compared to those with < 1 WLM. The ERR per 100 WLM for cancer mortality (excluding lung cancer) was 0.02 (95% CI=-0.01 to 0.05). No statistically significant increased risks with increasing exposure were found for bladder, colorectal, pancreatic, and stomach cancer. Overall, these findings provide modest evidence that radon progeny contributes to increased risks of cancer mortality (excluding lung cancer) among fluorspar miners. However, the precision of the estimates is limited by the small size of the cohort, which restricts the ability to draw firm conclusions regarding specific cancer sites. Future research should consider pooling data from radon-exposed occupational cohorts to better understand the association between radon exposure and the risk of cancers other than lung cancer.

Gamma Chamber 5000 (GC-5000) is a dry storage irradiator manufactured by the Board of Radiation and Isotope Technology, India. The GC-5000 can be employed as a facility for sample irradiation and dosimeter calibration purposes because of its dose distribution which is more homogeneous than that of large-scale gamma irradiators. However, optimizing the calibration service requires an in-depth understanding of the dose mapping within the sample chamber. This study aimed to demonstrate the applicability of a simulation using the Monte Carlo (MC) Proton Heavy-Ion Transport Code System (PHITS) software for determining the dose distribution within the GC-5000 irradiator at the Institute of Nuclear and Chemistry Technology (INCT), Poland, to validate the results in experiments using alanine dosimetry. Five measurement points were defined, with each point carrying four alanine dosimeters simultaneously irradiated in an in-house phantom manufactured from polymethyl methacrylate (PMMA). The in-house phantom and alanine dosimeters were additionally simulated with PHITS. The GC-5000 chamber was modeled consistently with the original GC-5000 design, which included the configuration of 44 Co-60 pencil sources and their activities. The relative differences between simulation and experiment for the five-point measurements were 0.7 % and 7.0 % for the minimum and maximum, respectively. The position with the best agreement was at the centre of the in-house PMMA phantom. It was found that the results of the MC simulation and the experimental dose mapping agreed. It is concluded that both methods can be used to precisely determine the dose rate at defined positions within the GC-5000. It is concluded that the methodology developed in this study, i.e., the integration of MC modeling and alanine dosimetry, provides a validated and practical approach for dose mapping and may serve as a reference for similar compact irradiators used in radiation processing. The methodology can also be extended to optimize other industrial radiation processing facilities, as it provides a robust framework for accurate dose calibration and dose rate mapping.

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.