Contribution of building materials to indoor external exposure: Development of a novel comprehensive evaluation tool and results

Breast compression thickness and composition affect radiation dose in digital mammography and tomosynthesis.

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.

Despite neonatal radiosensitivity, accurate lens dose assessments in computed tomography (CT) are lacking. We assessed the neonatal head CT eye lens dose under various scanning conditions, including vertical table displacement and organ-based exposure modulation (OEM), using the GAFCHROMIC LD-V1 (LD-V1), which can measure two-dimensional dose distributions, and we evaluated the limitations of conventional dose indices. The lens dose decreased with increasing distance from the isocentre for the Canon 320. Whereas, for the Canon 80 and Siemens, the dose peaked at +25mm and then decreased. For the OEM, the dose reduction effect decreased at 30°. The CT dose index volume remained consistent. Spatially resolved dosimetry using the LD-V1 reveals beam overlap and positioning-related dose anomalies that cannot be captured by point dosimeters or conventional indices. The LD-V1 can effectively evaluate superficial dose distributions and guide dose optimization in neonatal imaging.

Pediatric patients are highly radiosensitive, and technical variation in chest radiography can substantially affect dose. Fukushima prefecture also faces persistent post-disaster radiation concerns and declining pediatric imaging experience due to demographic change. A 5 year-old anthropomorphic phantom with 50 radiophotoluminescent dosimeters was examined at 22 facilities. Organ absorbed doses and entrance surface air kerma (ESAK) were directly measured, and effective dose was calculated using International Commission on Radiological Protection Publication 103 tissue weighting factors. One statistical outlier identified by Tukey's extreme outlier criterion was excluded from outlier-excluded analyses. Across 22 facilities, ESAK ranged from 0.03 to 1.25 mGy (median 0.12 mGy) and effective dose from 3.4 to 180.1μSv (median 27.3μSv). After exclusion of one outlier, ESAK ranged from 0.03 to 0.26 mGy (median 0.12 mGy; 9-fold variation) and effective dose from 3.4 to 94.2μSv (median 27.2μSv; 28-fold variation). The 75th-percentile ESAK was 0.137 mGy, 2.5% below Japan diagnostic reference levels 2025 (0.14 mGy), although 5 of 21 facilities (23.8%) exceeded this level. Median effective dose was 1.4-fold higher than the international reference value (20μSv). Compared with posterior-anterior (PA) projection, anterior-posterior projection showed higher breast dose (151.8 ± 74.3 vs 18.6 ± 10.7μGy;p= 0.0011) and higher effective dose (55.9 ± 29.6 vs 21.7 ± 11.5μSv;p= 0.0059); the stomach dose difference was exploratory (p= 0.025), whereas the thyroid dose difference was not statistically significant (p= 0.050). Tube current-time product correlated positively with effective dose (r= 0.67,p< 0.001). Marked inter-facility variation indicates substantial opportunities for optimization through greater use of PA projection, appropriate source-to-image receptor distance extension, and careful mAs adjustment. In post-disaster regions with declining pediatric imaging experience, radiation protection may require integrated technical, educational, and societal support.

&#xD;Radiotherapy during pregnancy is clinically challenging due to concerns about fetal radiation exposure. Proton therapy (PT) with pencil beam scanning can reduce out-of-field dose compared with photon therapy; however, secondary neutron production requires accurate fetal dosimetry.&#xD;Approach:&#xD;This study presents the design, material characterization, and computational modeling of two anatomically realistic pregnant anthropomorphic phantoms, MaTORI10 and MaTORI30, representing 10 and 30 weeks of gestation and developed for fetal dose assessment in PT. Candidate materials for lung, soft tissue, and bone-including commercial phantom materials, QA materials, and novel 3D-printed or castable polymers-were evaluated using MCNP 6.2 Monte Carlo simulations and compared with reference pregnant-tissue compositions. Depth-dose distributions, neutron yields, and out-of-field neutron spectra were analyzed to characterize radiological behavior. Suitable materials were implemented in physical phantoms constructed by integrating 3D-printed components and cast bone into an ATOM® female phantom. Pregnancy geometries from the University of Florida pregnant phantom library were merged with ATOM CT and surface scans to generate anatomically realistic models with detector inserts. Voxelized computational versions were generated from CT and surface scans and implemented in TOPAS 3.8. A virtual PT brain irradiation plan (78-116 MeV, 10 cm range SOBP, 5 cm modulation, 3 cm radius), with and without a range shifter (RS), was used to quantify in-field and fetal doses.&#xD;Main Results:&#xD;Material testing showed substantial variability, primarily driven by differences in hydrogen content and density. Both phantoms were successfully constructed and validated by CT imaging. For MaTORI30, modeled fetal dose was on average 29% higher without RS and 21% higher with RS compared to reference materials; for MaTORI10, increases of 10% and 18% were observed.&#xD;Significance:&#xD;The MaTORI10 and MaTORI30 phantoms provide the first anatomically detailed, pregnant anthropomorphic phantoms whose tissue-equivalent properties were computationally characterized for fetal dose assessment in PT. These phantoms provide a platform for experimental and Monte Carlo-based assessment of fetal dose, facilitating safer radiotherapy and optimal planning for pregnant patients.&#xD.

Air pollution associated with public transport systems constitutes a critical yet highly heterogeneous component of urban exposure and represents an important challenge for sustainable urban mobility and environmental health governance. Commuters and transport workers are frequently subjected to pollutant concentrations that exceed those reported by ambient background monitoring networks. This review provides a comprehensive synthesis of the global scientific literature on air quality in public transport microenvironments—including buses, bus stops, terminals, and underground stations—through a multidimensional analytical framework that considers climatic classification, socio-economic context, meteorological drivers, transport microenvironment typology, sampling strategies, analytical techniques, and exposure metrics. A large body of peer-reviewed studies published worldwide was examined to identify dominant patterns, methodological trends, and persistent knowledge gaps. Across regions, the evidence consistently reports elevated concentrations of particulate matter (PM2.5, PM10, and ultrafine particles) and traffic-related gaseous pollutants, particularly within confined or poorly ventilated environments and during peak traffic periods. Marked geographical, climatic, and socio-economic imbalances are evident, with most studies conducted in temperate and tropical climates and in countries with very high or high Human Development Index, whereas arid, continental, and low-HDI regions remain substantially underrepresented. From a methodological perspective, the literature is dominated by short- to intermediate-term monitoring campaigns relying on active sampling, mobile measurements, and increasingly calibrated low-cost sensors, while long-term stationary observations and standardized integrative monitoring frameworks remain scarce. Although advanced analytical approaches—such as chemical characterization, environmental magnetism, receptor modeling, computational fluid dynamics, and inhaled dose assessment—are increasingly applied, their systematic integration remains limited. Overall, this review reveals persistent methodological, geographical, and conceptual gaps and highlights the urgent need for standardized, interdisciplinary, and long-term monitoring strategies to improve exposure assessment and support evidence-based mitigation policies and sustainable urban transport planning aimed at reducing health risks associated with public transport-related air pollution.

In proton beam therapy (PBT) for hepatocellular carcinoma (HCC), deep learning (DL)-based dose prediction offers clinical value by providing immediate reference dose distributions as a guideline tool for treatment planners and enabling virtual PBT dose assessment at institutions lacking PBT facilities to support clinical decision-making. This study proposes a dose gradient-aware DL training approach and a beam arrangement-free framework that predicts dose distributions from computed tomography (CT) images and target/organs-at-risk structures without requiring beam arrangement inputs. Using data from 172 HCC patients, we systematically compared 20 DL models combining five architectures with four loss functions, including a novel dose gradient-aware loss capturing PBT-specific dose distribution characteristics arising from the Bragg peak. Prediction accuracy was evaluated using dose metrics for clinical target volume, planning target volume, and normal liver, 10% dose region volume assessment, visual examination, Dice similarity coefficient (DSC) for 10% dose region, and dose-volume histogram (DVH) analysis. DL models employing dose gradient-aware loss demonstrated reduced prediction errors in target volume dose metrics, achieved the lowest errors in 10% dose region volume when combined with U-Net (MAE: 35.4cm3, RMSE: 51.3cm3), attained the highest DSC (0.88 ± 0.05), showed the closest DVH agreement with clinical plans for both target structures and normal liver. A comprehensive evaluation consistently confirmed the superiority of dose gradient-aware loss across all metrics, demonstrating the importance of physics-informed, dose gradient-aware learning for accurate PBT dose distribution prediction. Particularly, DL models combining simple architectures with dose gradient-aware loss predicted doses that closely approximated clinical doses in PBT.

ABSTRACT Adolescents are highly susceptible to fluoride toxicity, yet evidence on renal effects and safety thresholds is limited and inconsistent. Data from adolescents aged 12–19 years in the 2015–2016 National Health and Nutrition Examination Survey (NHANES) were used in this study. The sample sizes were 1,042 for urinary fluoride (UF), 1,062 for plasma fluoride (PF), and 916 for drinking-water fluoride (WF). We analyzed associations between fluoride exposure (UF, PF, and WF) and renal function. Methods included survey-weighted linear/logistic regression, restricted cubic splines (RCS), inverse probability treatment weighting, trend tests, and Bayesian Benchmark Dose modeling (BBMD). RCS indicated linear relationships (P-nonlinear >0.05). Weighted linear regression showed significant inverse associations of UF (β = −11.16 (−20.10, −2.22), P = 0.029) and PF (β = −5.04 (−9.45, −0.62), P = 0.036) with estimated glomerular filtration rate; WF was non-significant (P = 0.585). The 10% benchmark concentration (BMC1 0) for UF was 1.63 mg/L (10% Benchmark Concentration Lower bound (BMCL1 0): 1.25 mg/L); for PF, BMC1 0 was 0.46 μmol/L (BMCL1 0: 0.24 μmol/L). These renal BMC values were lower than bone-derived benchmarks. Future regulations on environmental fluoride exposure should consider non-skeletal health effects in vulnerable populations.

This invited commentary grew out of a presentation made at the 2025 ConRad Meeting in Munich, Germany, and summarizes talks made by researchers supported by the National Institute of Allergy and Infectious Diseases (NIAID) and the Bundeswehr Institute of Radiobiology (BIR) during a joint programmatic workshop held on September 11-12, 2024. The symposium focused on the global health readiness and responses to radiological or nuclear public health emergencies; the status of medical countermeasure development and models used to develop these countermeasures; identification of biomarkers of radiation injuries and biodosimetry tools, and recent advances in developing tools for triage, definitive dose assessment and predictive assays. Areas of common synergy between the two entities were also explored to inform potential future collaborative efforts. There are many tools at different stages of development, and emergence of substantive datasets that require cutting-edge machine learning approaches, multiparametric analyses, and integrated systems outcome to fully exploit the potential of this knowledge and accurately address radiological emergency preparedness. In these endeavors, now more than ever, it is critical to continue connecting with the world's scientific communities to accelerate scientific breakthroughs, close research gaps, and enhance radiation emergency readiness.

The tin industry in Indonesia is a major global producer, and mining and smelting processes can mobilize and concentrate Naturally Occurring Radioactive Materials (NORM), particularly radionuclides from the 238U and 232Th decay series, potentially leading to occupational radiation exposure. We conducted a comprehensive assessment of annual effective doses to workers by integrating external and internal exposure pathways at two tin smelters using raw materials with different tin contents. External exposure was evaluated using ambient dose equivalent rate measurements, while internal exposure was assessed through simultaneous measurements of radon (222Rn), thoron (220Rn), and thoron progeny concentrations with passive discriminative detectors. Activity concentrations of 226Ra, 232Th, and 40K in raw materials and by-products were determined by HPGe gamma spectrometry to identify dominant contributors to gamma radiation fields. The total annual effective dose for most workers was <2 mSv, but reached 20.72 mSv for slag handling at one site, exceeding the recommended IAEA occupational limit. Radionuclides from the 232Th decay chain were the dominant contributors to external gamma exposure, particularly in slag, with activity concentrations increasing from raw materials to slag by approximately 28-fold for 226Ra and 79-fold for 232Th at Smelter A. Internal exposure was mainly influenced by thoron progeny in smelting areas, whereas radon contributed more in office and laboratory environments. These results identify slag storage as a critical radiological hotspot and highlight the need to evaluate both exposure pathways to support ALARA-based protection strategies and regulatory frameworks for NORM management in industrial settings.

Background: Tomotherapy systems employ image-guided radiotherapy (IGRT) using either megavoltage (MVCT) or kilovoltage (kVCT) computed tomography for daily patient positioning verification. However, these imaging procedures can deliver a non-negligible radiation dose to the patient. According to the American Association of Physicists in Medicine (AAPM) Task Group 180, this dose should be incorporated into the prescribed treatment dose if it exceeds 5%. Objectives: This study aimed to assess IGRT imaging doses and determine whether the cumulative dose exceeded 5% of the prescribed treatment dose. Materials and methods: Imaging doses from IGRT were evaluated under clinical scan protocols across four tomotherapy machines at three centers, including two MVCT systems and two kVCT systems. Doses were measured as Weighted Multiple Slice Average Dose (MSADw) using a CTDI phantom. Cumulative imaging dose was calculated by multiplying MSADw by the number of imaging sessions, then compared to the prescribed dose for each patient. Results: The mean MSADw values for MVCT ranged from 0.85 to 0.86 cGy per scan, while for kVCT it ranged from 0.19 to 2.65 cGy per scan. Over the treatment course, cumulative imaging doses accounted for 0.34-0.44% of the prescribed dose for MVCT and 0.28-0.87% for kVCT. Notable inter-center variations were observed, with differences of up to 51.16% in breast cancer cases and 35.71% in prostate cancer cases. Conclusion: Cumulative imaging doses from both MVCT and kVCT across all centers remained below the 5% threshold, indicating no need to adjust the prescribed dose in clinical practice. Nevertheless, further studies are required to identify the causes of inter-center variations and to develop optimized imaging protocols aimed at minimizing patient dose while maintaining adequate image quality.

Background: The increasing use of computed tomography (CT) has led to a substantial rise in population exposure to ionizing radiation, highlighting the need for accurate and individualized dose assessment methods. This study aimed to evaluate a novel dosimetric parameter—the size-specific dose–length product (DLPss)—in low-dose chest CT (LDCT) protocols and to compare its performance with conventional dose metrics. Methods: A retrospective single-center analysis was conducted in a cohort of 221 patients undergoing LDCT of the chest. Anthropometric parameters were used to calculate the size-specific conversion factor (k), enabling determination of SSDE and DLPss. Dose parameters (CTDIvol, DLP, SSDE, and DLPss) were analyzed and compared with data from a standard chest CT cohort (n = 134) from the first study in the series. The contribution of the topogram to total radiation dose was also assessed. All examinations were considered diagnostically adequate in routine clinical evaluations. Results: The mean CTDIvol in the LDCT group was 1.33 mGy, with a DLPss of 61.93 mGy·cm and an estimated effective dose below 0.7 mSv, representing a dose reduction exceeding 82% compared to standard CT. DLPss values were approximately 23% higher than conventional DLP, indicating underestimation of dose by standard metrics. The topogram accounted for 10.23% of total radiation dose in LDCT, significantly higher than in standard CT (1.84%). Significant sex-related differences were observed in CTDIvol, DLP, and DLPss, but not in SSDE. Conclusions: DLPss provides a more comprehensive and individualized assessment of radiation exposure than conventional dose metrics by integrating patient size and scan length. The substantial contribution of the topogram to total dose in LDCT highlights the need for its optimization, particularly in long-term screening programs. From a clinical perspective, implementation of DLPss may improve patient-specific risk stratification and support more precise monitoring of cumulative radiation exposure, especially in populations undergoing repeated imaging, such as lung cancer screening cohorts. Advanced reconstruction algorithms, including deep learning-based methods, may enable further dose reductions and warrant future clinical investigation.

The increasing utilization of biomass for energy production leads to the generation of significant amounts of ash, creating both challenges and opportunities for sustainable management. The objective of this study is to explore the potential application of biomass ash from a radiological perspective in Austria. A total of 51 biomass ash samples, including combustion ashes and gasification residues, were collected from five companies, with sampling sites distributed across Austria. The activity concentrations of 226Ra, 232Th, 40K, and 137Cs were measured using gamma-ray spectrometry with high-purity germanium detectors, while 90Sr was analyzed in seven samples after chemical separation using liquid scintillation counters. A comprehensive understanding of the radionuclides contained in the ash is essential to determine the optimal utilization options. The activity concentration index for gamma radiation emitted by building materials according to the EU Directive 2013/59/EURATOM, as well as extended indices including 137Cs, were calculated to determine suitable utilization pathways for the ash in circular economy applications such as cement production and forest fertilization, with different indices ranging from (0.0156 ± 0.0014) to (3.1 ± 0.2). A conservative dose assessment was conducted for a worker handling biomass ash in Austrian industrial plants to evaluate the potential radiation exposure, determined as (0.384 ± 0.073) mSv per year. This value is well below the 1 mSv per year effective dose limit for public exposure, as specified in EU Directive 2013/59/EURATOM, indicating negligible occupational exposure and no radiation protection arrangements deemed necessary.

Comparison of different methods for the assessments of effective dose due to gamma radiation emitted by building materials

FLASH radiation therapy is a promising modality that delivers radiation at ultra-high dose rates, potentially minimizing normal tissue toxicity while maintaining tumor control. However, conventional dosimetry tools often fail at ultra-high dose rates, necessitating alternative solutions. Alanine dosimetry, a passive technique known for its dose-rate independence and tissue equivalence, presents a compelling option. While other studies have used alanine pellets, this study investigates the applicability of alanine powder dosimeters in FLASH radiation therapy. Thirteen dosimeters were irradiated with doses from 10 to 100 Gy using a 137 Cs source. Six samples were used to construct dose-response calibration curves, while the remaining seven were used for validation. Peak-to-peak amplitudes of the electron paramagnetic resonance signal were normalized using internal standards and sample density. Dose estimates based on density-normalized calibration were within ±4.2% of expected values, demonstrating strong linearity (R 2 > 0.99) and clinical viability. While post-processing time remains a limiting factor, this work affirms the potential of alanine powder as a reliable tool for FLASH dosimetry, especially for high-dose, dose-rate-independent measurements.

In comparison to conventional medical computed tomography (CT), cone-beam CT (CBCT) has become widely used in dental and maxillofacial applications due to its accurate 3D information, high resolution, minimal radiation dose, and affordable machine cost. In this study, we investigated the image quality and radiation doses of dental CBCT and X-ray machines developed in Thailand. Our in-house reconstruction algorithm including artifact reduction was based on GPU calculations of filtered backprojection and was significantly faster than a CPU-based algorithm. The image quality aspects for CBCT were evaluated in terms of high contrast resolution, gray value uniformity, noise, and geometric accuracy, while image quality assessment for 2D images included high contrast resolution, low contrast levels, and distortion rate. Radiation doses were measured and calculated for the dose-area product (DAP). The technical image quality and radiation dose assessment was compared with those of other commercial extraoral imaging machines. The findings demonstrate that, when compared to other units, the proposed 2D and 3D extraoral imaging systems yielded comparable technical image quality and radiation doses. Based on these results, the Thai-made 2D and 3D extraoral imaging machines appear suitable for further clinical evaluation.

Patients with meningeosis carcinomatosa or primary brain tumors may require craniospinal irradiation. In craniospinal volumetric modulated arc therapy (VMAT-CSI), field junctions are sensitive regions prone to underdosage. This study investigated whether global, planning target volume (PTV)-based quality metrics can detect such localized deficits and how different field-overlap widths affect junction dosimetry. Retrospective computed tomography datasets from six patients were analyzed. For each patient, VMAT-CSI plans with overlap lengths of 4, 6, 8, 10, and 12 cm were generated. Dose coverage (D98%) and homogeneity index (HI) were evaluated for the PTV and a junction-focused subvolume (PTV-VOI). Conformity indices (RTOG, Salt-Lomax, Lomax, and Van't Riet) were calculated for both structures. Increasing overlap improved D98% for both PTV and PTV-VOI. While the PTV often met D98% ≥95% at small overlaps, adequate PTV-VOI coverage was achieved only at ≥10 cm. VOI-based RTOG and Salt-Lomax indices increased with overlap, the Lomax index decreased slightly, and Van't Riet remained stable. Global PTV-based indices showed minimal variation. Adequate dose coverage at the field junctions in VMAT-CSI treatment is achieved with field overlaps of 10-12 cm. Since global PTV metrics mask local underdosages, clinicians should use VOI assessments at the field junctions rather than relying solely on global plan indices.

Computational retrospective dosimetry with fortuitous dosimeters: An inter-laboratory comparison and evaluation of dose conversion coefficients

Chest radiography is essential in neonatal intensive care units (NICUs), but repeated exposures raise concerns due to the high radiosensitivity of newborns. This study aimed to estimate entrance skin dose (ESD) and absorbed organ doses in neonates undergoing chest X-ray examinations, under varying exposure parameters, using Monte Carlo simulation. A realistic NICU scenario was modeled in MCNP6.3 Monte Carlo code, including a mobile X-ray unit, an incubator, and ICRP 143 neonatal reference phantoms. Simulations were performed for tube voltages ranging from 45 to 65 kV and radiation field sizes of 10 × 10 , 15 × 15, and 20 × 20 cm 2 . Experimental validation was carried out using a water phantom and a solid-state dosimeter. ESD ranged from 15.36 to 59.81 μ Gy, with a mean of 36.45 μ Gy. Absorbed organ doses varied widely: brain (0.14–1.31 μ Gy), lens (0.13–1.33 μ Gy), esophagus (6.46–52.51 μ Gy), stomach (25.50–118.40 μ Gy), liver (13.98–78.64 μ Gy), red bone marrow (0.71–10.50 μ Gy), kidneys (2.89–25.23 μ Gy), thyroid (1.82–29.59 μ Gy), and lungs (4.88–39.46 μ Gy). Dose increases were driven primarily by higher tube voltages and, most significantly, by the inclusion of the organ within the primary beam. These findings highlight the importance of strict collimation and optimized parameters in neonatal radiography, reinforcing the ALARA principle. • Organ doses were determined using MCNP6.3 and ICRP 143 neonatal phantoms. • We modeled a complete NICU scenario, with incubator and mobile X-ray unit. • Stomach received the highest mean absorbed dose (54.44 μ Gy). • Organ doses peaked in liver and stomach. • Field size of 20 × 20 cm 2 raised liver dose by over 5-fold.