A modified beam-flattening filter design for the 147Pm beta source of the irradiation facility Beta Secondary Standard BSS-2 has been developed to achieve substantially improved dose-rate uniformity, targeting ±5% or better over the required phantom area. The study was performed using the Monte Carlo simulation codes EGSnrc and PHITS. The proposed filter design demonstrates a significant enhancement in dose-rate homogeneity at a calibration distance of 20 cm compared with the existing International Organization for Standardization (ISO)-recommended filter (ISO 6980 standard series). The dose-rate uniformity improved from approximately ±8% to nearly ±1% within a circular region of radius 7.5 cm, while simultaneously increasing the absolute central dose-rate by ~30%.
The increasing use of I-124 PET for differentiated thyroid cancer (DTC) has raised concerns about radiation exposure in pediatric patients because of their radiosensitivity. This study estimated organ-absorbed doses and the lifetime attributable risk (LAR) of secondary cancer following I-124 PET using Monte Carlo simulations with pediatric voxel phantoms representing 10- and 15-year-old males and females. Organ doses were calculated for oral and intravenous administration under different thyroid uptake conditions, and LAR was estimated using the Biological Effects of Ionizing Radiation (BEIR) VII model. The thyroid absorbed dose was slightly higher after intravenous administration, whereas the total-body dose depended mainly on age. Younger patients showed nearly twice the LAR of older patients. Females had a higher solid cancer risk, whereas leukemia risk was greater in males. Thyroid uptake and administration route had minimal effect on LAR. These findings support individualized I-124 PET protocols to maximize diagnostic benefit while minimizing long-term radiation risk in pediatric DTC.
Diagnostic cerebral angiography for intracranial aneurysms can deliver relatively high patient radiation doses, and locally derived diagnostic reference levels (DRLs) are important for optimization. This retrospective single-center study analyzed 186 procedures performed at Vajira Hospital between 2022 and 2024 using a biplane digital subtraction angiography system. Dose-area product (DAP), cumulative air kerma (CAK), fluoroscopy time, number of image frames, and number of three-dimensional rotational angiography (3DRA) acquisitions were recorded for each procedure. Median values across all years served as local typical dose values and were compared with published 75th percentile DRLs, consistent with the International Commission on Radiological Protection (ICRP) 135. The medians were 58.58 Gy·cm2 (DAP), 326.74 mGy (CAK), 6.41 min (fluoroscopy time), 525.50 frames, and 3.00 3DRA acquisitions, with no significant interannual differences. Typical values for DAP, CAK, and fluoroscopy time were lower than those reported in several national and international studies, indicating comparatively low patient doses.
This study investigates the long-term vertical migration of 137Cs in undisturbed grassland soil using a unique 40-year monitoring dataset (1987-2026) from Northern Greece established after the Chernobyl accident. Fractional 137Cs depth distributions measured in six 5 cm soil layers (0-30 cm) were analysed using a parsimonious 1D process-based model incorporating advection, hydrodynamic dispersion, and an effective irreversible transfer from a migrating to a fixed phase. Model parameters were estimated through hybrid global-local optimization, and their uncertainty was evaluated by residual bootstrap analysis. A single parameter set successfully reproduced the temporal evolution of all measured depth profiles, yielding strong overall agreement with observations. The estimated effective transport parameters were an advective migration velocity of 0.217 ± 0.093 cm y-1, a dispersion coefficient of 0.24 ± 0.48 cm2 y-1, and an effective fixation coefficient of 0.0365 ± 0.0178 y-1. The dispersion coefficient exhibited substantial uncertainty because of the limited vertical resolution (5 cm) sampling intervals, whereas the fixation parameter was more robustly constrained and represents the residual long-term transfer required to reproduce the observed profile evolution after the initial rapid postdepositional fixation period. These results demonstrate that a parsimonious process-based model provides an effective description of the long-term redistribution of 137Cs at the monitored undisturbed grassland site in Northern Greece.
Astronaut radiation exposure in low Earth orbit is strongly affected by orbital radiation environment, shielding condition, and radiation quality. In this study, a Geant4-based Monte Carlo model coupled with the adult male mesh-type reference computational phantom of the International Commission on Radiological Protection (ICRP) was developed to estimate organ doses for astronauts in the Chinese Space Station (CSS) orbit. Proton and electron spectra from the Earth's radiation belts (ERB) were calculated using AP9/AE9, and solar-minimum galactic cosmic ray (GCR) spectra were generated using CREME96. Organ absorbed dose, $Q(L)$-based organ dose equivalent and effective dose equivalent were calculated for two representative exposure scenarios: extravehicular activity (EVA) with spacesuit-equivalent shielding and intravehicular activity (IVA) with spacecraft shielding. The calculated effective dose equivalent rates in the CSS orbit were 1006 μSv d-1 during EVA and 571 μSv d-1 during IVA. ERB protons were the dominant contributor to organ absorbed dose and effective dose equivalent under both shielding conditions. ERB electrons contributed mainly to superficial tissues during EVA and were almost completely attenuated under IVA conditions. After spacecraft shielding, GCRs became more important for dose-equivalent-based quantities because of their high penetration capability and high-LET components. The calculation method was evaluated by additional ISS-orbit simulations and comparison with MATROSHKA measurements and previous PHITS calculations. Good agreement was obtained for IVA exposure, whereas larger deviations during EVA were mainly associated with simplified local shielding geometry and the sensitivity of superficial tissue doses to low-energy ERB particles. The comparison between CSS and ISS orbits showed that astronaut dose levels cannot be inferred from orbital altitude alone, because different orbital inclinations lead to different ERB and GCR spectra. The present results provide organ-specific dose data for astronauts in the CSS orbit and support radiation protection assessment for future long-duration missions.
This study presents an 8-y (2017-2024) integrated environmental radioactivity monitoring program and public dose assessment conducted across the entire Emergency Planning Zone (EPZ) of the Hanbit Nuclear Power Plant in the Republic of Korea. Following the expansion of the EPZ to a 30 km radius, a comprehensive multi-media monitoring framework was established, covering rainwater, surface soil, seawater, and locally produced foodstuffs. To our knowledge, this study represents one of the first EPZ-scale, integrated multi-media environmental radioactivity datasets in Korea, enabling a systematic evaluation of spatial and temporal variability across multiple environmental pathways. Radionuclides of interest included beta activity, cesium-137, and tritium, analyzed under metrologically validated conditions in accordance with ISO 11929 and IAEA guidelines. Temporal and spatial analyses indicated that radionuclide concentrations across all environmental matrices remained within the range of natural background variability, with no statistically significant long-term trends (P > .05). Occasional fluctuations were attributed to environmental factors such as precipitation patterns and marine dynamics rather than anthropogenic releases. Public radiation dose assessments, based on realistic exposure pathways including ingestion and external exposure, showed that the annual effective dose to residents within the EPZ was well below regulatory limits and international reference levels. The integration of long-term, multi-media monitoring data with dose assessment provides a robust framework for distinguishing natural background variability from potential anthropogenic contributions. These findings demonstrate the radiological safety and environmental stability of the Hanbit EPZ and highlight the value of EPZ-scale, system-based monitoring approaches for nuclear facility surveillance and public reassurance.
The Institute of Applied Nuclear Physics conducts periodic monitoring of doses for occupationally exposed workers in Albania. This is the first study in Albania that includes all regional and university hospitals in the country. Measurements are carried out in 2-month periods using thermoluminescent dosemeters composed of LiF:Mg,Ti crystals which are measured with the Harshaw 6600 and Harshaw 4500 reader. The results indicate that the average dose for the years 2021 to 2025 is 0.62 mSv y-1 and collective annual dose is 243.7 man mSv averaged for 5 years, where 393 occupationally exposed workers like doctors, physicists, radiologists, etc. are monitored. The results indicate that the doses are within the limits, and comparable to worldwide occupational doses. The dose distribution for the year 2025 for all employees fits well with the q-Gaussian distribution, consistent with heterogeneity of doses which comes from different workload, different equipment's etc.
Static magnetic fields are present around high-voltage direct-current transmission facilities, but on-land environmental measurement data under actual operating conditions remain limited. This study measured three-axis magnetic flux densities at 1.0 m above ground at 38 accessible locations around all four operating direct-current transmission links in Japan, including overhead-line and underground-cable sections. Resultant magnetic flux densities ranged from 39.7 to 154.8 μT, while measured local geomagnetic-field levels ranged from 46.6 to 50.6 μT. The maximum value was observed above the Anan-Kihoku Link underground-cable section and was far below the International Commission on Non-Ionizing Radiation Protection (ICNIRP) reference level for general public exposure to static magnetic fields. Lateral-profile measurements showed that values near the lines or cable routes diminished to local geomagnetic-field levels within several tens of metres. Geomagnetic-field-aware calculations were generally consistent with representative measured profiles, although underground-cable comparisons were sensitive to cable-centreline uncertainty. These data support static magnetic-field exposure assessment around operating direct-current transmission facilities.
Diagnostic reference levels (DRLs) for positron emission tomography (PET/CT) examinations have not previously been established in Costa Rica, and data from Central America remain limited due to the restricted availability of PET/CT systems in the region. This study established local DRLs for administered 18F-FDG activity and CT dose metrics in 393 adult lymphoma patients undergoing PET/CT at the Cyclotron-PET/CT Laboratory (Centro de Investigación en Ciencias Atómicas, Nucleares y Moleculares), University of Costa Rica. DRLs were defined as the 75th percentile (P75), and the influence of patient body mass was assessed. The DRL for administered activity was 388.5 MBq (4.8 MBq kg-1). Whole-body CT DRLs were 12.1 mGy for Volume Computed Tomography Dose Index and 1250.2 mGy cm for dose-length product, while thorax CT DRLs were 8.5 mGy and 325.6 mGy cm, respectively. Dose metrics increased with patient body mass, whereas normalized activity values remained consistent with international practice. These findings provide the first PET/CT-specific DRLs for Costa Rica and support future national dose optimization and monitoring efforts.
This study presents a radioprotection assessment for an ultra-high dose rate accelerator installation in one of the animal housing of the Centre for Advanced Preclinical in vivo Research. The main problem concerns the absence of a bunker while limiting exposure in nearby work areas. The geometry of the accelerator, the building layouts and the distribution of the environmental dose equivalent were simulated with FLUKA.CERN 4-4.1, modeling a 9 MeV electron beam. The results confirmed compliance with the limit of 0.250 mSv/year for unrestricted areas during daytime operation. Night-time operating zone restrictions apply when no staff are present, allowing beam on for quality controls. The effective doses to the population, researchers and workers are less than 1 mSv/year, in accordance with Legislative Decree 101/2020; the accelerator operators are classified as exposed. For small animals, precautionary dose limit of 1 mSv/year was adopted. The use of lead shielding and site-specific safety measures ensure radiological compliance.
This study established diagnostic reference levels (DRLs) for common adult single-photon emission computed tomography (SPECT) procedures in Bahrain to support dose optimization and alignment with international radiation protection standards. Data were retrospectively collected from two major nuclear medicine centers, representing most national SPECT services. Administered radiopharmaceutical activities (MBq) for adult patients (70 kg ± 20%) undergoing routine examinations were analyzed. DRLs were calculated as the 75th percentile of administered activity following International Commission on Radiological Protection (ICRP) Publication 135. A total of 1098 studies were included. Variations between centers reflected differences in administration practices. Overall, Bahrain's proposed DRLs were lower than regional values reported in Kuwait and Saudi Arabia and were comparable to European benchmarks. The findings provide a national reference framework for optimization of nuclear medicine practice and support ongoing monitoring to maintain compliance with international radiation safety recommendations from the ICRP and International Atomic Energy Agency.
Radon is an environmental carcinogen, a well-known leading cause of lung cancer, second only to smoking. Despite its health significance, public awareness and knowledge about radon is limited in many developing nations, including Nigeria. This study therefore assessed the level of radon awareness and knowledge among students of Dennis Osadebay University in Asaba, Nigeria. The study employed a cross-sectional survey using a structured questionnaire consisting of 30 items. Out of 942 respondents, only 45.4% had prior awareness of radon, while 54.6% had never heard of it. Widespread misconceptions about radon knowledge were noticed with only 17.3% correctly recognized lung cancer as the major health risk of radon exposure. The findings revealed a generally low levels of radon awareness and knowledge among the students. This highlights a significant gap in environmental health literacy, underscoring the overbearing need for educational interventions, public awareness campaigns, and national radon policy in Nigeria.
BACKGROUND:Positron Emission Tomography/Computed Tomography (PET/CT) is a crucial imaging modality widely used for diagnosing and staging various cancers. Although patient weight is known to influence radiation dose, there is limited research on optimizing PET/CT protocols based on weight categories to minimize unnecessary exposure. OBJECTIVES:This study evaluates the effective dose for common PET/CT scans at Penang Hospital, with a particular focus on the influence of patient weight on both PET and CT dose components. Additionally, the study assesses whether weight-based dose protocols can contribute to dose optimization. METHODS:This retrospective study analyzed 1439 PET/CT scans performed at Penang Hospital. The effective dose was calculated using International Commission on Radiological Protection (ICRP) 103, 106, and 128 dose coefficients. Conversion factors used were 0.019 mSv/MBq for 18F-FDG, 0.0199 mSv/MBq for 68Ga-PSMA, and 0.021 mSv/MBq for 68Ga-DOTATATE. The CT dose component was estimated using the dose-length product (DLP) with an empirical conversion factor (k = 0.015 mSv·mGy-1·cm-1) for whole-body CT. RESULTS:The total effective dose for 18F-FDG (head-to-thigh and head-to-feet) scans was 12.34 and 16.38 mSv, respectively. For 68Ga-PSMA and 68Ga-DOTATATE scans, the total effective dose was 11.55 and 12.00 mSv, respectively. A statistically significant increase in dose was observed in heavier patients due to increased administered activity and CT parameters (P < .05). Weight had a smaller impact on PET dose in 68Ga-PSMA and 68Ga-DOTATATE compared to 18F-FDG. CONCLUSION:Patient weight significantly influences the total effective dose in PET/CT examinations. These findings highlight the importance of considering patient-specific factors when evaluating radiation dose in clinical practice.
This study experimentally evaluates extremity doses from unintentional exposure emitted by handheld X-ray fluorescence (XRF) analyzers. Although handheld XRF devices are widely used for material analysis, quantitative assessments of unintentional exposure remain limited. Mockup experiments were conducted using a Thermo Scientific NITON XLt 797 analyzer and a polymethyl methacrylate hand phantom equipped with radiophotoluminescent glass dosemeters (GD-302M). Spectrometric measurements were performed with a CdTe detector, and photon fluence spectra were unfolded using the MAXED code with Particle and Heavy Ion Transport code System-generated response functions. The mean X-ray energy was 28.4 ± 0.03 keV, with characteristic molybdenum peaks at ~17.5 keV (Kα) and 19.6 keV (Kβ). For a typical 30-s analysis, the estimated personal dose equivalent Hp(0.07) at the point of contact was ~95 μSv. The Hp(0.07) on the dorsal side was roughly one-fifth of the palmar dose. Ambient dose equivalent rates measured directly from the XRF device may reach high enough to set radiation-controlled areas, underscoring the need for strict handling protocols. These findings demonstrate the importance of radiological protection education and awareness when using handheld XRF devices.
Accurate calibration of biological dosimetry methods is crucial for reliable radiation dose assessment in both medical and research contexts. However, discrepancies in calibration coefficients (α, β, c) across various studies impede standardization and the comparability of dose-response curves. This study conducted a systematic analysis of calibration data from 62 studies covering different radiation types (60Co gamma rays, 137Cs gamma rays, and X-rays) with varying energies and dose rates (0.00196-23.85 Gy/min), to explore the sources of variability and their effects on dicentric chromosome yields. Using descriptive statistics, analysis of variance, Kruskal-Wallis tests, and correlation analyses, we found significant differences in α and β coefficients across different dose rate categories for 60Co gamma rays (P < .05). Specifically, the α coefficient increased from 0.022 ± 0.015 at low dose rates (0-0.5 Gy/min) to 0.049 ± 0.021 at higher dose rates (>1 Gy/min). Moreover, no significant differences were detected between the Computer-Assisted Brain Analysis System (CABAS) and Dose Estimate software for estimating coefficients (P > .05 for α, β, c), indicating consistency in the methodological outputs of these software tools. The observed variability was attributed to factors such as radiation quality, experimental protocols, and inter-laboratory differences. These findings highlight the necessity for standardized calibration protocols that take radiation parameters into account. We propose the development of harmonized experimental setups and reference curves to improve comparability across studies, ultimately enhancing the accuracy of biological dosimetry for radiation protection and epidemiological research. In alignment with existing International Atomic Energy Agency and International Organization for Standardization (ISO) guidelines and acknowledging that international ring-trial intercomparisons remain essential for ensuring comparability across laboratories.
While essential for precision in image-guided radiation therapy (IGRT), kilovoltage (kV) cone beam computed tomography (CBCT) contributes a cumulative radiation dose to organs at risk. This study quantifies absorbed organ doses in head-and-neck IGRT, emphasizing the benefit of optimized anatomy-specific protocols. Using OSLDs in an anthropomorphic phantom, we measured doses for two dedicated head-and-neck protocols (Standard S10/CBCT2 and Low-dose S20/CBCT3). Additionally, a non-optimized chest protocol (CBCT1) was evaluated to quantify the dosimetric penalty of potential protocol misapplication. The misapplied chest protocol resulted in severe overexposure (spinal cord dose $\approx $ 81 mGy per scan). In contrast, the optimized head-and-neck protocols maintained organ doses below 20 mGy per scan. Comparing the optimized protocols, the Standard S10 provided a balanced dose profile, while the Low-dose S20 reduced exposure but showed higher variability near bone interfaces. Results show that strict adherence to anatomy-specific protocols is a critical radiation protection imperative to avoid unnecessary exposure.
Eleven building materials (95 samples in total) have been analyzed for 226Ra, 228Ra (232Th series), and 40K activity using High Purity Germanium (HPGe) spectrometry, and concentrations are found to be in the range (2.2-549), (0.3-161), and (2.7-1034) Bq kg-1, respectively. Statistical analyses showed a moderate positive linear correlation between 226Ra and 228Ra, and significant differences in the mean radionuclide concentrations among ceramic tile, brick, granite, and the other studied materials. Radiation hazard indices (radium equivalent activity, external and internal hazard index, activity concentration index, dose rate) were determined to assess the potential health risk. Several samples of granite, ceramic tile, and brick showed individual indices exceeding the recommended maximum values. The discriminant analysis clearly separated granite, brick, and ceramic tile from the other materials, while the principal component analysis showed that the component explaining >84% of the data variance is strongly correlated with loading of 226Ra.
This study developed and evaluated novel high-density concrete shields (HDCS) to protect the radiosensitive ocular lens during head computed tomography (CT). Five formulations with varying polypropylene and lead fibres were tested using anthropomorphic phantoms and clinical patients (n = 35). The lead-free M1 formulation (9.2 kg/m3 polypropylene) was optimal, achieving ~35% reduction in patient ocular lens dose across both CT acquisition protocols. Quantitative American College of Radiology phantom tests confirmed maintained CT number accuracy, uniformity, and spatial resolution. Qualitative radiologist assessment found minimal anterior artefacts that did not affect diagnostic interpretation of central or posterior brain structures. The M1 HDCS is a viable, potentially cost-effective shielding alternative, ideal for routine head CT where orbital detail is not the primary focus.
In diagnostic computed tomography (CT), radiological technologists and assisting staff may need to remain inside the CT room during patient assistance. Understanding temporal changes in scattered radiation distribution is therefore important for reducing occupational exposure. Conventional measurements mainly provide instantaneous dose rates or accumulated doses and are less suited to intuitively capturing temporal changes during CT scanning. This study conducted a fundamental investigation of a visualization approach, defined as dynamic dose distribution (DDD), based on time-resolved air kerma measurements obtained with a semiconductor survey meter. Scattered radiation was measured during chest-to-pelvis helical CT scanning of an anthropomorphic phantom under fixed tube current and automatic exposure control conditions. DDD allowed temporal changes in scattered radiation distribution to be visually identified in relation to tube current modulation, patient table position, and measurement height. DDD may provide useful temporal information for considering staff positioning and reducing occupational exposure.
