Health physics最新文献

The accidental ingestion of radioactive iodine is known to increase the risk of thyroid cancer and thyroid dysfunction; hence, strict radiation safety measures are required when handling it. In a previous study, we demonstrated that absorbing radioactive-iodine-containing wastewater using a water-absorbent polymer with cyclic oligosaccharides that selectively capture iodine, followed by natural drying, effectively separates at least 80% of the iodine from the wastewater. However, because natural drying requires approximately 2 wk, faster processing is essential to improve the efficiency of this wastewater treatment. Hence, we propose a method for quickly separating iodine from wastewater via heat drying. This study aimed to compare radioactive iodine volatilization levels between samples subjected to heat-drying- and natural-drying-based iodine and water separation. Na 125 I was added to purified water and artificial urine to prepare simulated waste liquids containing iodine at concentrations equivalent to those in the urine of patients undergoing radioactive iodine treatment. The prepared simulated waste liquids were poured into containers containing a superabsorbent polymer, dried in a thermostatic dryer set at 100 °C for 9 h, and subsequently stored for 90 d. The iodine residual rate in the simulated waste liquids was determined by measuring 125 I radioactivity. At the end of the heat-drying process, the iodine residual rates in the simulated waste liquids prepared with purified water and artificial urine were 0.452 and 0.783, respectively. When absorbed in 1 g of superabsorbent polymer, the residual rates increased to 0.956 and 0.952, respectively. Over the following 82 d, the residual rates decreased by approximately 10%. Thus, by absorbing radioactive-iodine-containing wastewater into a highly water-absorbent polymer and then applying heat drying, iodine can be effectively separated from the wastewater while limiting its volatilization to less than 15%.

Conventional occupational radiation exposure monitoring relies on cumulative dose data from personal dosimeters without providing information on when, where, or under what conditions exposure occurs. This lack of context limits analysis of causal factors, evaluation of protective behaviors, and the effectiveness of safety education. This study aimed to develop and clinically implement an integrated information system for occupational radiation exposure by combining dose data, spatiotemporal movement records, and angiography-related radiation information. We also assessed its utility and potential for improving radiation safety management. The system was implemented for 1 mo in a clinical angiography suite. It integrated (1) personal digital dosimeters recording dose and time, (2) Bluetooth Low Energy beacons tracking healthcare workers' positions and movements, and (3) Radiation Dose Structured Reports providing exposure details. Data were synchronized to reconstruct when, where, and under what conditions exposure occurred. The system identified high-risk positions near x-ray tubes (Beacon IDs 1-3), where exposure was greatest. Avoidance behaviors were also detected, such as movement to low-risk areas (e.g., Beacon ID 8) before irradiation. We successfully developed, implemented, and evaluated the system, demonstrating its utility for improving radiation safety management. The insights gained support targeted interventions and the refinement of safety protocols, with potential for broader use in diverse radiation-controlled settings.

Nearly 400 million years ago, vertebrate life began to transition from a purely aquatic existence to the terrestrial environment. Concurrently, exposure to ionizing radiation from cosmic and geologic sources increased substantially. Around the same time, vertebrate hematopoietic stem cells (HSCs) migrated from the liver and peri-nephric parts of the abdomen into the interior of bones. Interestingly, among today's vertebrates, only fish lack bone marrow. All other extant vertebrates maintain their HSCs in the bone marrow cavity. We propose protection from sub-lethal DNA damage to these long-lived radiation-sensitive cells because of exposure to ionizing radiation is why HSCs are sequestered with the bone marrow cavity. Our calculations support this hypothesis. Residence in the bone marrow cavity reduced exposure to penetrating background radiation and the concomitant DNA damage by at least 20%. This reduction was even more significant radio-biologically when considering the relatively hypoxic conditions within the bone marrow cavity and oxygen's role in enhancing radiogenic DNA damage. This may be particularly relevant considering the oxygen-rich atmosphere in existence at the time of transitioning to a terrestrial habitat. Given the exquisite sensitivity of HSCs and proliferating blood cells to radiation, we propose this translocation provided a selective advantage and that protection from sub-lethal radiogenic DNA damage at least partially explains translocation of hematopoietic cells to the bone marrow cavity in terrestrial vertebrates.

End-of-life (EOL) management of high-activity radioactive sources is made uniquely challenging by the inherent risks associated with storage and transportation of these sources, the complex logistics involved, and the strict requirements for regulatory compliance. Traditional methods lack comprehensive tools for accurate site assessments and precision planning for the transportation of radioactive sources. They also frequently fail to provide the adaptability required to consider diverse operational environments, resulting in inefficiencies and potential safety concerns. This paper introduces a novel software solution developed to address these issues by integrating advanced technologies such as light detection and ranging (LiDAR)-based 3D environment modeling, smart dynamic route planning, and customizable measurement functionalities. This software enables detailed terrain visualizations, facilitating thorough environmental assessments and enabling users to virtually navigate, analyze, and plan site-specific operations. Among the key features are a user-centric interface for virtual navigation, precise site measurement tools for site evaluations, interactive visualizations that highlight potential operational hazards, dynamic route planning capabilities, and real-time collision detection to promote safe workflows. By demonstrating the effectiveness of this tool through real-world application, the present work underscores the tool's potential to revolutionize radioactive source EOL management by improving operational efficiencies, minimizing risk, and advancing the state of practice to achieve suitable and secure radioactive material handling.

This study establishes a robust and clinically applicable calibration protocol for optically stimulated luminescence dosimeters (OSLDs) in diagnostic radiology, with the aim of improving the accuracy of patient dose assessment. A total of 144 OSLDs were systematically irradiated under controlled conditions to assess their dosimetric response across a wide range of tube voltages (40-150 kVp) and square field sizes (10 × 10 cm² to 30 × 30 cm²). The dosimeters exhibited a sensitivity variation of ±6.6%, with an average background dose of 0.0185 mGy. The experimental data revealed a high dependence of OSLD response on photon energy, with dose values increasing by a factor of 11.5, from 0.1393 mGy at 40 kVp to 1.6072 mGy at 150 kVp for a constant field size of 10 × 10 cm². A pronounced non-linear dose escalation was observed in the mid-kVp range (70-100 kVp), where dose measurements increased by 72-90% as field size expanded. Energy and geometry-specific correction factors were derived, showing significant variation with field size, reaching maximum values of 9.81 for the 30 × 30 cm² field at 150 kVp and 7.43 for the 10 × 10 cm² field under the same conditions. Additionally, notable discrepancies were observed between experimentally derived effective beam energies and reference values reported by the International Atomic Energy Agency (IAEA), highlighting the need for localized calibration standards. These findings contribute to the standardization of OSLD calibration protocols in diagnostic radiology and support their implementation for accurate patient dose monitoring in clinical settings.

The anticipated increase in nuclear decommissioning in the coming decades requires innovative approaches to maintain worker exposure as low as reasonably achievable. Occupational dose, an important component of cost-benefit analysis and work planning in decommissioning, can be estimated using radiation transport codes. Monte Carlo N-Particle (MCNP) is a robust, well-established code that has been used to model a breadth of geometries and source terms. Attila4MC offers a graphical user interface for users to build and run MCNP simulations and create an unstructured mesh of computer-aided design (CAD) models with tunable meshing parameters, including element edge length bounds and curvature refinement features. To understand how these parameters might be optimized for a large-scale model for dose estimation, a building containing gloveboxes, a hot cell, ventilation, robotic characterization tools, and operators was modeled in a CAD program. Source terms from available literature were applied to the equipment, and the operator dose was tracked for several exposure geometries. Mesh parameters, including maximum edge length (MEL) bounds, curvature refinement part selection, d/h ratio, and minimum edge length, were varied, and the resulting dose estimates were compared. The upper MEL bound had little effect on the estimated dose rate, but the varying the lower bound resulted in a 40% change in dose rate compared to the default case. Curvature refinement increased the MCNP figure of merit very slightly, about 2.6% when applied globally, but increased by over 31% when applied to only selected parts within the model. Both minimum edge length and d/h ratio showed a maximum change in dose rate of 10% compared to the default case for the values investigated in this study. Finally, the dose rate results suggest that the use of robotic or remote characterization methods may reduce occupational dose to workers by several orders of magnitude for the modeled scenario.

The Moroccan radiopharmaceutical industry is currently under development. The country has two operational cyclotrons capable of producing fluorine-18-labeled radiopharmaceuticals (RPs), primarily for PET imaging, while all other therapeutic and SPECT-dedicated RPs are imported. Importation processes are administratively complex and subject to fluctuations in global supply chains. The RP industry also faces additional challenges, including a stringent regulatory framework, limited accessibility, reimbursement barriers, and a scarcity of trained professionals in radiopharmacy and nuclear medicine more broadly. Furthermore, limited education and awareness among referring clinicians hinder the integration of some nuclear medicine procedures into routine clinical practice. Despite these challenges, Morocco has significant potential for localized RP production. Strategic investment and partnerships with key international agencies could enhance radiopharmacy infrastructure, streamline regulatory pathways for local manufacturing, and foster the development of new training programs for professionals in Morocco and other African countries.

In radiation safety programs, particularly in large healthcare systems, personal dosimetry is often issued conservatively, leading to unnecessary monitoring of individuals with minimal exposure risk. This study describes a structured approach implemented at Mayo Clinic to evaluate the necessity and exchange frequency of dosimeters using two years of retrospective radiation dose data. Personnel were grouped based on job type and workplace conditions, then dosimetry data was analyzed at the 50th percentile, 95th percentile, and maximum levels against conservative thresholds. Regulatory requirements and managerial input were incorporated throughout the decision-making process. From 2020 to 2024, this method resulted in the reduction of dosimeter frequency for 82 individuals and complete removal for 1,067: reducing dosimeter issuance by 4,912 each year. The approach enabled a more efficient use of resources, allowing radiation safety efforts to be directed toward higher-risk groups and activities without compromising compliance or worker protection. This model provides a conservative, scalable framework for optimizing dosimetry programs in healthcare and potentially other radiation-using industries.

According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) publications, contributions of terrestrial gamma doses are mainly from the presence of 40K, and of 238U and 232Th together with their progeny in various rocks and soils. A survey of soil distributions of radionuclides 40K, 238U, and 232Th was performed at the Nevada National Security Site (NNSS) using in situ gamma-ray spectrometry with a high-purity germanium (HPGe) detector. The average activity concentrations of 40K, 238U, and 232Th in natural soils at the NNSS are 867 Bq kg-1 (range from 150 ± 8 to 1297 ± 56 Bq kg-1), 50 Bq kg-1 (range from 29 ± 3 to 74 ± 8 Bq kg-1), and 56 Bq kg-1 (range from 11 ± 2 to 96 ± 10 Bq kg-1), respectively. The concentration at each location is significantly associated with its geological lithology. The terrestrial gamma dose rates around the NNSS were estimated from 26 to 144 nSv h-1 with mean value of 93 nSv h-1. Our results provide useful information about the natural background radiation and radiological effects of naturally occurring radionuclides at the NNSS.

Substitute materials that accurately reproduce the radiological properties of human tissues are required for direct in vivo measurement of internally deposited radioactive materials to estimate associated health risk, especially for the respiratory tract. The Livermore torso phantom, the de facto standard for calibrating detector systems that measure radioactive materials deposited in the lungs, liver, and thoracic lymph nodes, was designed with tissue substitute materials that match the density and attenuation coefficient exhibited by natural human tissue when exposed to single low-energy x rays associated with the decay of plutonium. In this study, we evaluated the radiometric tissue equivalence of new tissue substitutes for muscle, rib, sternum, lung, and cartilage that are suitable for a continuous low photon energy spectrum from approximately 30 to 120 keV. The formulation for each of the tissue substitutes was developed using a novel method that determines the optimized quantity of base material and additives to produce a material that best matches the density and photon transmission exhibited by the natural human tissue present in the thoracic cavity. Measurements of the mass attenuation coefficient (i.e., ) from approximately 30 keV up to 120 keV for each substitute tissue were within 8% or better to expected values calculated using the photon cross section database XCOM from the National Institute for Standards and Technology.