Search Results (364)

Background/Objectives: Optimizing routine neurointerventional workflow and minimizing exposure to ionizing radiation during coil-only endovascular treatment of intracranial aneurysms depend on operator experience, reduced frame rates during both fluoroscopy and digital subtraction angiography (DSA), and the use of advanced angiographic systems. The low-dose protocol implemented in this study used the lowest available fluoroscopy frame rate (3.125 frames per second [fps]) and a nominal acquisition rate of 2 fps (actual = 2.45 fps) for DSA, three-dimensional (3D) rotational angiography, two-dimensional (2D)/3D mapping, and roadmapping. Methods: This retrospective analysis encompassed 245 coil-only procedures performed at a single tertiary center from 2018 to 2024. Data collected for each procedure included dose-area product (DAP), reference air kerma (K_a,r), fluoroscopy time (FT), and the total number of DSA frames. Local diagnostic reference levels (DRLs; 75th percentile [P75]) and typical values (50th percentile [P50]) were determined and descriptively compared with values reported in the literature. Results: The P75 values, representing DRLs, were 22.4 Gy·cm² for DAP (literature range, 123–272.8 Gy·cm²), 268 mGy for K_a,r (1171–4240 mGy), 18 min 56 s for FT, and 285 DSA frames. The P50 values were 13.8 Gy·cm² for DAP (78.7–179.0 Gy·cm²), 196 mGy for K_a,r (801–2804 mGy), 13 min 25 s for FT, and 208 DSA frames. Conclusions: In this single-center cohort, dose metrics for coil-only intracranial aneurysm treatment were within the lower range of published values. Cross-study comparisons are descriptive and require cautious interpretation. The proposed local DRLs may support quality assurance, dose optimization, and patient safety in comparable clinical settings. Further multi-center and multi-operator studies are warranted to evaluate transferability and applicability beyond coil-only procedures. Full article

Objective: Mobile head CT enables bedside neuroimaging in critically ill patients, reducing risks associated with intrahospital transport. Despite increasing clinical use, evidence on dose optimization for mobile CT systems remains limited. This study evaluated whether an optimized CT protocol can reduce radiation exposure without compromising diagnostic image quality in neurointensive care unit patients. Methods: In this retrospective single-center study, twenty-two non-contrast head CT examinations were acquired with a second-generation mobile CT scanner between March and May 2023. Patients underwent either a default (group A, n = 14; volumetric computed tomography dose index (CTDI_vol) 44.1 mGy) or low-dose CT protocol (group B, n = 8; CTDI_vol 32.1 mGy). Regarding dosimetry analysis, we recorded dose length product (DLP) and effective dose (ED). Quantitative image quality was assessed by manually placing ROIs at the basal ganglia and cerebellar levels to determine signal, noise, signal-to-noise ratio, and contrast-to-noise ratio. Two neuroradiologists independently rated qualitative image quality using a four-point Likert scale. Statistical comparisons were performed using a significance threshold of 0.05. Results: Median DLP and ED were significantly lower for group B (592 mGy·cm, 1.12 mSv) than for group A (826 mGy·cm, 1.57 mSv; each p < 0.0001). Quantitative image quality parameters did not differ significantly between groups (p > 0.05). Qualitative image quality was rated excellent (median score 4). Conclusions: The optimized mobile head CT protocol achieved a 28.7% reduction in radiation exposure while maintaining high diagnostic image quality. These findings support the adoption of low-dose strategies in mobile CT imaging in line with established radiation protection standards. Full article

Space conditions offer new insights into fundamental biological and molecular mechanisms. The study aimed to evaluate the enzymatic activity of proteinase K (PK) under extreme conditions relevant to space environments: simulated microgravity, hypergravity, and gamma radiation. PK activity was tested using azocasein (AZO) as a chromogenic substrate, with enzymatic reactions monitored spectrophotometrically at 450 nm. A rotating wall vessel (RWV) simulated microgravity, centrifugation at 1000× g (3303 rpm) generated hypergravity, and gamma radiation exposure used cesium-137 as the ionizing source. PK activity showed no remarkable changes under microgravity after 16 or 48 h; however, higher absorbance values after 96 h indicated enhanced AZO proteolysis compared to 1 g (Earth gravity) controls. In hypergravity, low PK concentrations exhibited slightly increased activity, while higher concentrations led to reduced activity. Meanwhile, gamma radiation caused a dose-dependent decline in PK activity; samples exposed to deep-space equivalent doses showed reduced substrate degradation. PK retained enzymatic activity under all tested conditions, though the type and duration of stress modulated its efficiency. The results suggest that enzyme-based systems may remain functional during space missions and, in some cases, exhibit enhanced activity. Nevertheless, their behavior must be evaluated in a context-dependent manner. These findings may be significant to advance biotechnology, diagnostics, and the development of enzyme systems for space applications. Full article

Protons are conventionally regarded as a low-linear energy transfer (low-LET) radiation modality with a relative biological effectiveness (RBE) of 1.1, suggesting direct mechanistic similarity to X-rays in the underpinning biological effects. However, exposure to spread-out Bragg peak (SOBP) protons reveals instructive deviations from this assumption. Indeed, proton beams have a maximum LET of ~5 keV/µm but display reduced reliance on classical non-homologous end joining (c-NHEJ) as well as an increased dependence on homologous recombination (HR) and alternative end joining (alt-EJ). These features are well described in cells exposed to high-LET radiation and typically manifest between 100 and 150 keV/µm. We hypothesized that this apparent discrepancy reflects biological consequences of proton-beam properties that remain uncharacterized. In the present study, we outline exploratory experiments aiming at uncovering such mechanisms. We begin by investigating for both entrance and SOBP protons the dose-dependent engagement of HR we recently showed for X-rays. Consistent with our previous findings with X-rays, HR engagement after exposure to both types of proton beams declined with dose, from ~80% at 0.2 Gy to less than 20% at higher doses. RAD51/γH2AX foci ratios, reflecting HR engagement, were modestly higher following proton irradiation, in line with increased HR utilization. G₂-checkpoint activation, previously linked to HR, was also stronger after exposure to protons, as was DNA end resection. Moreover, the formation of structural chromosomal abnormalities (SCAs) was higher for SOBP than entrance protons and X-rays. Collectively, our results suggest quasi-high-LET characteristics for proton beams and raise the question as to the physical proton properties that underpin them. We discuss that the commonly employed definition of LET may be insufficient for this purpose. Full article

Radon (²²²Rn) is a naturally occurring radioactive noble gas that is a major source of ionising radiation in the environment. Many measurement techniques can be used to monitor ²²²Rn concentrations in the workplace. The main purpose of conducting such measurements is to identify locations of exposure, determine the effective dose for workers and, if necessary, define actions for reducing the exposure. As part of this study, a series of measurements were conducted in the underground tourist route at Książ Castle in Poland. The route has been open to visitors since late 2018. The measurements included long- and short-term tests. Passive and active methods were used to measure the ²²²Rn activity concentration. Additionally, the potential alpha energy concentration and ambient and radioactive aerosol size distributions were measured. Finally, the annual effective dose for workers was estimated. The dose was calculated while factoring in the legal regulations in the Czech Republic and Poland to demonstrate their effect on the final results. The obtained values were low—they did not exceed 0.218 mSv (for the specified exposure time)—indicating the effectiveness of natural ventilation and a low radiation risk to personnel. Full article

This systematic review evaluated the effectiveness of iterative reconstruction (IR) and deep learning reconstruction (DLR) in reducing radiation dose in computed tomography (CT) while preserving diagnostic image quality. We systematically searched PubMed, Scopus, and Web of Science (last search 22 March 2025); the protocol was registered in the OSF (DOI: 10.17605/OSF.IO/TUQDS). Eligible studies were English-language adult (≥18 years) investigations published between 2020 and 2025 that used IR or DLR and reported radiation-dose outcomes; studies on paediatric, phantom, cadaver, cone-beam, and spectral CT were excluded. In accordance with PRISMA 2020 guidelines, 4371 records were identified, and 30 met the inclusion criteria. Risk of bias was assessed using the NIH Quality Assessment Tool; most studies were deemed to be at low risk. Data were narratively synthesised and structured by a reconstruction approach and anatomical region. Across the 30 studies, IR achieved a dose reduction of 24–50% (mean ≈ 45%) and a DLR reduction of 34–89% (mean ≈ 58%); several DLR protocols enabled reductions of ≥75% without impairing diagnostic quality. Thirty studies in total were included (total N = 2581; range 24–289). It was determined that both approaches substantially reduce radiation exposure while maintaining diagnostic image quality; DLR generally demonstrates greater noise suppression and dose efficiency, especially in ultra-low-dose applications. However, heterogeneity in methods, designs, and scanner technologies limits the ability to draw uniform conclusions. Standardised protocols, multi-vendor prospective studies, and long-term evaluations are needed. Full article

Unlike high-dose scans, low-dose cardiac CT perfusion imaging reduces patient radiation exposure and thereby the risk of potential health effects. However, it introduces significant image noise, degrading diagnostic quality and limiting clinical assessment. Denoising is thus a critical preprocessing step to enhance image quality without compromising anatomical or perfusion details. Traditionally used reconstruction-domain methods, such as Iterative Reconstruction and Compressed Sensing, are often limited by algorithmic complexity, dependence on raw sinogram data, and restricted adaptability. Conversely, image-domain methods offer more adaptable denoising options. Recently, learning-based approaches have further expanded this flexibility and demonstrated state-of-the-art performance across various denoising tasks. In this work, we present a deep learning-based denoising method specifically tuned for low-dose cardiac CT perfusion imaging. Our model is trained to reduce noise while preserving structural integrity and temporal contrast dynamics, which are critical for downstream analysis. Unlike many existing methods, our approach is optimized for perfusion data, where temporal consistency is essential. Residual cardiac motion remains a separate challenge, which we aim to address in our future work. Experimental results show significant improvements in quantitative image quality, using both reference-based and no-reference metrics, such as MSE/PSNR/SSIM and NIQE/FID/KID, as well as improved accuracy of perfusion measurements. Full article

Radiotherapy is a fundamental component in the management of head and neck malignancies, but its non-selective effects on surrounding normal tissues can result in significant oral complications. The oral cavity and oropharynx contain several radiosensitive structures, including mucosa, salivary glands, and alveolar bone, which are susceptible to both acute and late toxicities resulting in mucositis, xerostomia, and osteoradionecrosis. Although dentomaxillofacial diagnostic imaging, such as intraoral radiography, panoramic imaging and cone-beam computed tomography (CBCT), delivers radiation doses several orders of magnitude lower than therapeutic exposures, its biological impact on previously irradiated tissues remains underexplored. Even low-dose X-rays may act as secondary stressors, reactivating oxidative and inflammatory pathways in tissues with compromised repair capacity. In this review, we examine the radiobiological and dosimetric implications of using diagnostic ionizing imaging in patients undergoing or recently having completed head and neck radiotherapy. We summarize current evidence on potential additive effects of low-dose imaging, emphasizing the importance of justification, timing, and protocol optimization. Finally, we discuss radioprotective strategies (e.g., dose modulation, field limitation, and integration of modern low-dose imaging technologies) designed to reduce unnecessary exposure, thus enhancing tissue preservation and ensuring diagnostic safety in this vulnerable patient population Full article

Low-dose computed tomography (LDCT) has become a widely adopted protocol to reduce radiation exposure during clinical imaging. However, dose reduction inevitably amplifies noise and artifacts, compromising image quality and diagnostic confidence. To address this challenge, this study introduces De-TransGAN, a transformer-augmented Generative Adversarial Network specifically designed for high-fidelity LDCT image denoising. Unlike conventional CNN-based denoising models, De-TransGAN combines convolutional layers with transformer blocks to jointly capture local texture details and long-range anatomical dependencies. To further guide the network toward diagnostically critical structures, we embed channel–spatial attention modules based on the Convolutional Block Attention Module (CBAM). On the discriminator side, a hybrid design integrating PatchGAN and vision transformer (ViT) components enhances both fine-grained texture discrimination and global structural consistency. Training stability is achieved using the Wasserstein GAN with Gradient Penalty (WGAN-GP), while a composite objective function—L1 loss, SSIM loss, and VGG perceptual loss—ensures pixel-level fidelity, structural similarity, and perceptual realism. De-TransGAN was trained on the TCIA LDCT and Projection Data dataset and validated on two additional benchmarks: the AAPM Mayo Clinic Low Dose CT Grand Challenge dataset and a private clinical chest LDCT dataset comprising 524 scans (used for qualitative assessment only, as no NDCT ground truth is available). Across these datasets, the proposed method consistently outperformed state-of-the-art CNN- and transformer-based denoising models. On the LDCT and Projection dataset head images, it achieved a PSNR of 44.9217 dB, SSIM of 0.9801, and RMSE of 1.001, while qualitative evaluation on the private dataset confirmed strong generalization with clear noise suppression and preservation of fine anatomical details. These findings establish De-TransGAN as a clinically viable approach for LDCT denoising, enabling radiation reduction without compromising diagnostic quality. Full article

Computed tomography (CT) is a major source of low-dose ionizing radiation exposure in medical imaging. Risk assessment at this dose level is difficult and relies on the hypothetical linear no-threshold model. To address the response to such low doses in patients undergoing CT scans, we examined radiation-induced alterations at the transcriptomic and DNA damage levels in peripheral blood cells. Peripheral whole blood of 60 patients was collected before and after CT. Post-CT samples were obtained 4–6 h after scan (n = 28, in vivo incubation) or alternatively immediately after the CT scan, followed by ex vivo incubation (n = 32). The gene expression of known radiation-responsive genes (n = 9) was quantified using qRT-PCR. DNA double-strand breaks (DSB) were assessed in 12 patients through microscopic γ-H2AX + 53BP1 DSB focus staining. The mean dose–length product (DLP) across all scans was 561.9 ± 384.6 mGy·cm. Significant differences in the median differential gene expression (DGE) were detected between in vivo and ex vivo incubation conditions, implicating that ex vivo incubation masked the true effect in low-dose settings. The median DGE of in vivo-incubated samples showed a significant upregulation of EDA2R, MIR34AHG, PHLDA3, DDB2, FDXR, and AEN (p ranging from <0.001 to 0.041). In vivo, we observed a linear dose-dependent upregulation for several genes and an explained variance of 0.66 and 0.56 for AEN and FDXR, respectively. DSB focus analysis revealed a slight, non-significant increase in the average DSB damage post-exposure, at a mean DLP of 321.0 mGy·cm. Our findings demonstrate that transcriptional biomarkers are sensitive indicators of low-dose radiation exposure in medical imaging and could prove themselves as clinically applicable biodosimetry tools. Furthermore, the results underscore the need for dose optimization. Full article

Objective: Chest computed tomography (CT) is a key component of the diagnostic assessment of people with cystic fibrosis (PwCF) and is increasingly replacing chest radiography. Due to improvements in life expectancy, radiation exposure has become a growing concern in PwCF. Photon-counting CT (PCCT) has the potential to reduce the risk of radiation-induced malignancies while maintaining diagnostic accuracy. This study aimed to compare the radiation dose and image quality of low-dose high-resolution (LD-HR) and ultra-low-dose high-resolution (ULD-HR) CT protocols using PCCT in PwCF. Methods: This retrospective study included 72 PwCF, with 36 undergoing a LD-HR chest CT protocol and 36 receiving an ULD-HR protocol on a PCCT. The radiation dose and image quality were assessed by comparing the effective dose and signal-to-noise ratio (SNR). Three blinded radiologists evaluated the overall image quality, sharpness, noise, and assessability of the bronchi, bronchial wall thickening, and bronchiolitis using a five-point Likert scale. Results: The ULD-HR PCCT protocol reduced radiation exposure by approximately 65% compared with the LD-HR PCCT protocol (median effective dose: 0.19 vs. 0.55 mSv, p < 0.001). While LD-HR images were consistently rated higher than ULD-HR images (p < 0.001), both protocols maintained diagnostic significance (median image quality rating of “4-good”). The average SNR of the lung parenchyma was significantly lower with ULD-HR PCCT compared to LD-HR PCCT (p < 0.001). Conclusions: ULD-HR PCCT significantly reduced radiation exposure while maintaining good diagnostic image quality in PwCF. The effective dose of ULD-HR PCCT is only twice that of a two-plane chest X-ray, making it a viable low-radiation alternative for routine imaging in PwCF. Full article

Background: Agents with free radical-scavenging functions may act as radiation modifiers, protectors, or mitigators. Methods: We investigated whether supplementation with resveratrol (RSV) in mice, at different times after the beginning of X-irradiation, may influence sperm count and quality during the irradiation and recovery. Results: Irradiation importantly decreased the sperm count. RSV supplemented with 1 Gy since 24 h increased sperm count. The combination of low doses increased, whereas the combination of high doses reduced DNA damage. Coadministration of two high doses since the eighth day significantly increased DNA damage and slightly increased sperm count. The supplementation of RSV during recovery was toxic to irradiated males. The sperm parameters were a little better in the absence of RSV. The degree of DNA injury of germ cells was importantly lower in groups combined with 1 Gy. Conclusions: Resveratrol counteracted the radiation-induced death of germ cells and improved the sperm count. RSV may function as radioprotector (before or during exposure) and radiomitigator (after exposure) of lethal effects in male gametes. The combination of high doses of irradiation with RSV over 24 h mitigated DNA damage. Contrarily, supplementation during recovery is not recommended since it may be toxic during long-lasting irradiation. Full article

Nuclear factor erythroid 2-related factor 2 (NRF2) is a key transcription factor that controls the antioxidant response to oxidative stress, especially after exposure to ionizing radiation (IR). This review examines NRF2’s emerging role as a complementary biomarker in radiobiological dosimetry for assessing radiation exposure and its potential health effects. When cells encounter IR, the resulting reactive oxygen species (ROS) interfere with the NRF2 repressor KEAP1, leading to NRF2 activation and the expression of cytoprotective genes such as HO-1, NQO1, and GCLC. Evidence suggests that NRF2 levels increase in a dose- and time-dependent manner, primarily at low to moderate radiation doses, highlighting its potential for early detection of radiation exposure. However, at high doses (>8 Gy), NRF2 activation may be suppressed due to apoptosis or irreversible damage, which limits its reliability in those situations. The review also compares NRF2 with other biomarkers used in biodosimetry, discussing its advantages, such as sensitivity and early response, along with its limitations, including variability in activation at high doses and expression influenced by other oxidative factors. The authors introduce a comprehensive radiobiological model that illustrates how low-dose IR exposure affects NRF2 expression patterns, thereby improving the understanding of dose-dependent oxidative stress mechanisms. Additionally, the role of NRF2 in inflammation and general health risk assessment is emphasized, suggesting broader applications beyond biodosimetry. Overall, NRF2 holds significant promise for use in evaluating radiation exposure, developing radioprotection strategies, and informing future radiobiological research frameworks. Full article

Melanoma is a highly aggressive skin cancer primarily linked to ultraviolet (UV) radiation. However, the potential role of ionizing radiation from radiotherapy in melanoma development remains unclear. This review synthesizes data from epidemiologic studies and case reports on melanoma after radiation exposure. Evidence indicates that childhood radiotherapy, even at low doses, is associated with an increased melanoma risk, plausibly reflecting the heightened radiosensitivity of developing melanocytes. Occupational radiation exposure, particularly in earlier eras with insufficient shielding, also appears to elevate risk. In patients exposed to radiation in adulthood, findings are mixed: large population datasets suggest a modest increase in melanoma following therapeutic radiation, whereas some case–control analyses do not demonstrate a clear dose–response relationship. UV radiation promotes melanomagenesis through direct DNA photoproducts driving characteristic C>T transitions at dipyrimidine sites, alongside oxidative stress and local immune modulation that facilitate malignant transformation. Collectively, individuals with prior radiotherapy, especially those irradiated in childhood, should be considered at increased melanoma risk and may benefit from long-term, targeted surveillance of irradiated fields. Awareness of this association between radiation exposure and melanoma may also support clinicopathologic correlation during the diagnostic evaluation of melanocytic lesions. Future work should define dose–response relationships in contemporary radiotherapy methods, characterize molecular signatures of ionizing radiation-associated melanomas, and establish evidence-based surveillance strategies for high-risk cohorts. Full article

The synergistic effects of stratospheric ozone depletion and climate change are intensifying surface ultraviolet-B (UVB) radiation, posing a severe threat to amphibians—one of the most endangered vertebrate groups globally. Xenopus laevis, with its cutaneous respiration and limited photoprotective mechanisms, exhibits high sensitivity to UVB, making it a suitable model for ecotoxicological studies. While UVB is known to cause DNA damage, immune suppression, and microbial dysbiosis, its mechanisms in multi-organ interactions, dose–response thresholds, and host–microbiome regulatory networks remain poorly understood. This study employed a gradient UVB exposure regime integrated with histopathology, oxidative stress assays, and 16S rRNA sequencing to systematically evaluate the effects of UVB on (1) cascade damage across skin, liver, and intestinal barriers; (2) immune cell distribution; (3) redox dynamics; and (4) microbial community structure and function. Our findings demonstrate that low-dose UVB activated compensatory antioxidant defenses without structural disruption, whereas exposure beyond a critical threshold induced nonlinear redox collapse, microbial dysbiosis, and multi-organ barrier failure, collectively exacerbating ecological adaptation risks. These results reveal a cross-scale mechanism by which UVB impairs amphibian health via disruption of host–microbe homeostasis, providing a conceptual and empirical framework for assessing species vulnerability under ongoing climate change. Full article