International journal of radiation biology最新文献

Purpose: The number of oxygen vacancies in quartz measured by electron spin resonance (ESR) as the intensity of the E₁' center has been used to investigate the provenance of the sediments and has been found to be a good proxy in discussing the direction and intensity of the wind system in the past. While its temporal variations have been examined using marine sediments. The present study aimed to show that terrestrial sediments are also useful for such studies on climate change when it is continuous.

Materials and methods: Samples from a continuous tephric loess sequence were examined in the present study. Samples were collected from Kamiyoshida outcrop in Rokunohe Town, Aomori Prefecture, with 5 cm intervals from 110 cm to 420 cm, and a total of 61 samples were analyzed. XRD (X-ray diffraction) analysis was employed to correct the content of quartz in the chemically processed samples.

Results and conclusions: Three peaks of the number of oxygen vacancies were observed (15-20, 40-50, and 70-75 ka) for the grain size fractions <2-20, and 20-50 µm. These three peeks look corresponding to the peaks in marine sediments observed in a previous work. During these periods, the amount of eolian dust supplied from the Chinese continent may have been larger, resulting in higher oxygen vacancy values in quartz in both sediments of Sea of Japan and of tephric loess sequence on land. The present results indicate that land sedimentary sequence would be as useful as marine sediments for studying past wind systems.

Purpose: Radiation-induced fibrosis (RIF) is a significant long-term complication of radiotherapy, affecting many cancer patients months to years after treatment. Characterized by progressive tissue stiffening, loss of elasticity, and impaired organ function, RIF can deleteriously impact a patient's quality of life. Commonly affected sites include the skin, lung, heart, and kidney. Advances in radiotherapy techniques, such as intensity-modulated radiation therapy (IMRT), stereotactic body radiotherapy (SBRT), and image-guided radiotherapy (IGRT), have improved the precision of radiation delivery, reducing acute damage to healthy tissues; RIF however, remains a prevalent complication despite these technological advancements. This review explores the underlying cellular and molecular mechanisms of RIF, emphasizing fibroblast proliferation, myofibroblast activation, and excessive extracellular matrix (ECM) deposition in its progression. Additionally, this review highlights in vitro and in vivo models that are instrumental in studying RIF and evaluates current therapeutic strategies aimed at mitigating RIF.

Conclusion: Radiation-induced fibrosis continues to affect a considerable number of patients due to the chronic nature of the fibrotic processes, driven by sustained fibroblast activation, ECM accumulation, and inflammatory responses. Newly developed approaches, such as stem cell-based therapies, TGF-β inhibitors, and molecular interventions aimed at ECM regulation, offer promising avenues for mitigating or reversing RIF. Additionally, integrating computational models into clinical practice could enhance personalized treatment planning, enabling better prediction and prevention of RIF in patients. Addressing these challenges is critical for improving the quality of life of patients affected by RIF and improving their outcomes, particularly with the growing population of long-term cancer survivors in the world.

Purpose: In case of an accidental or malevolent radiological event involving a large number of potential victims, fast and correct classification in terms of level of exposure is of utmost importance, not only for those that require specific medical treatment, but also for those that were not exposed. Our goal was to develop a system allowing to classify as many potential victims as possible in our laboratory by using the reference cytogenetic biodosimetry assay.

Materials and methods: A system was created with a theoretical classification of 320 individuals 13 days after sample reception by using a triage-mode dicentric chromosome assay (DCA). After preliminary tests to verify the system logistics and equipment, a partial-capacity exercise was performed, where 120 blood samples were irradiated with 6 MV X-rays at doses ranging from 0 to 4.5 Gy. Operators were asked to treat and analyze the blindly coded samples by applying specific protocols and to respect an established deadline.

Results: Deployment of the system was successful and pre-planned logistics were applied as instructed. Classification results were compiled with a strict time limit and following previous developments, 3 radiation exposure grading scales of 5, 4 and 3 classes were applied. Correct classification ranged from 85 to 92%, depending on the grading scale used.

Conclusions: This partial-capacity exercise contributed to validate the newly developed organizational system, showing promising results. Points of improvement were clearly identified, and current efforts are focused toward maximizing the correct classification percentage and testing the maximal capacity of the system.

Purpose: Phosphorylation of the histone H2AX (γ-H2AX) is a rapid response to radiation-induced DNA double strand breaks (DSBs) and is a good biomarker for exposure to ionizing radiation. The signal has traditionally been detected by microscopy (spot counting) or by flow cytometry (fluorescent intensity). An imaging flow cytometry (IFC) method has been developed, which combines the high resolution of microscopy with the statistical power of flow cytometry methods to measure γ-H2AX in human lymphocytes.

Materials and methods: The assay was optimized and validated for both sample acquisition and data analysis, in the dose range of 0-10 Gy. For data analysis, mean fluorescence intensity (MFI), spot count (foci per cell), and average area of the spots were used with the supervised machine learning (SML) K-Nearest Neighbors (K-NN) algorithm to estimate doses. These dose estimates were compared to the traditional flow cytometry method of estimating doses from an MFI-based dose response curve.

Results: A statistical analysis of both methodologies showed that SML K-NN method was able to determine the dose delivered to blind, irradiated samples more accurately than when using a linear fit of the MFI response alone, especially in the 7-10 Gy dose range.

Conclusions: The efficiency of the γ-H2AX-IFC assay, 1 hour post-exposure, has been improved and validated using the SML K-NN methodology for dose estimation. This study could help establish the γ-H2AX assay as a triage tool for the rapid screening of a large number of samples.

Purpose: To apply electron spin resonance (ESR) dosimetry to wild Japanese macaques captured in the ex-evacuation area during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the improvement of the detection limit is crucial. In this study, we optimized the microwave power in ESR measurements to suppress the noise of native radicals and enhanced the signals of radiation-induced carbonate radicals.

Materials and methods: Tooth enamels of a Japanese macaque captured in a control area were prepared and irradiated with gamma rays from ⁶⁰Co source. The ESR spectra of the enamel samples with different absorbed doses ranging from 0 to 1800 mGy were measured with varying microwave power. The ESR spectra were analyzed by an in-house multi-component decomposition code using a simulated annealing method.

Results: Intensities of both components originating from carbonate and native radicals saturated and decayed as the microwave power increased. The intensity ratio of carbonate radicals to native radicals, i.e., signal to noise ratio, increased monotonically at microwave powers below 30 mW. We also examined the linearity of the intensity of carbonate radicals against the absorbed doses and recommended a microwave power range of 5-25 mW.

Conclusion: In this study, we showed that optimizing the microwave power is an effective way to improve the quantitation accuracy of carbonate radicals in samples with low absorbed doses. The improved measurement conditions will expand the applicable range of ESR dosimetry for research on the effects of radiation on wild animals related to the FDNPP accident.

Purpose: This paper characterizes types of biodosimetric tools used for response and treatment in a large-scale nuclear event. Using US official documents to define dangerous zones and centers for triage and treatment, the types of biodosimetry needed in various circumstances, based on likely volumes, types of radiation and extent of combined injuries of people arriving at different center locations, are defined.

Conclusions: Appropriate biodosimetry methods should consider the type of radiation received (predominantly prompt mixed gamma-neutron irradiation or gamma rays from fallout), probability of physical injury/burns, the likelihood of receiving a significant dose, and the location and number of likely victims. The types of parameters needed for using biodosimetric techniques most effectively in a nuclear event, including for methods to be developed, are denoted for seven distinct situations that would occur with a large-scale nuclear event. The analysis leads to the conclusion that the benefit of using qualitative biodosimetry for stage 1 triage of people who were in dangerous zones is low and not recommended in a nuclear detonation. For this cohort, stage 2 triage will be very important but the type of biodosimetry depends on whether the irradiation occurred immediately or from fallout, because anyone from the detonation zones would more likely have physical injuries and/or burns and have received neutron exposures. Biodosimetry in stage 3 (medical care) would have only a modest role. Biodosimetry for people nearby but outside of the detonation and fallout zones requires a different approach, perhaps also benefitting from new methods.

Purpose: The development of AI-assisted biodosimetry systems brings significant advances in cytogenetic dosimetry. The introduction of deep learning algorithms has improved the accuracy and speed of chromosome detection and classification in input images, addressing the incomplete reproducibility and time-consuming of manual evaluation. An advanced molecular cytogenetic technique, PNA-FISH, has further improved the clarity and reliability of chromosome identification. We have been developing a deep learning algorithm to automate the detection of chromosomal aberrations in PNA-FISH images, resulting in a more efficient approach to dose assessment, particularly in large-scale nuclear disasters.

Conclusion: Integrating AI-assisted biodosimetry systems into the cooperative framework among Advanced Radiation Emergency Medical Support Centers in Japan is expected to support dose assessment in the events of nuclear disasters with mass casualties. However, there are still challenges in the integration of the system into our cooperative framework. Temperature management during blood transport is crucial to prevent coagulation and ensure adequate lymphocyte counts. To improve performance of our AI model, it is necessary to standardize experimental procedures for chromosome image preparations among network members and to further train the learning model. The development of secure and convenient data sharing system is also essential to improve the integrated and practical operation of the network and reduce its running costs. Additionally, development of a user-friendly interface is helpful for all the network members to operate the AI model. We will continue to develop web-based applications for AI-based biodosimetry by considering these requirements to enhance the effectiveness of the biodosimetry network of Japan.

Purpose: Cytogenetic biodosimetry of the Partial Body Irradiation (PBI) requires a dose response curve (DRC) for chromosome aberrations (ChA) but also an exponential coefficient D₀ of the interphase cell survival (ICS) of irradiated lymphocytes. The aim of the present work was to construct joint DRCs in vitro for ChA and ICS and validate them in a setting with a limited number of blood donors.

Materials & methods: Blood samples from three healthy volunteers were irradiated in vitro with 6 MV Linac photons to a range of acute doses up to 5.46 Gy. Cytogenetic preparations were stained with Fluorescence-plus-Giemsa; ChA were scored in the first division metaphases. The ICS was assessed in PBI simulations, mixing irradiated and unirradiated blood 1:1 at each dose point; D₀ was estimated by regression analysis.

Results: The DRC for dicentrics had linear and quadratic coefficients, respectively, 0.031 × cell^-1 × Gy^-1 and 0.070 × cell^-1 × Gy^-2; for dicentrics plus centric rings - respectively, 0.033 × cell^-1 × Gy^-1 and 0.083 × cell^-1 × Gy^-2. The ICS parameter D₀ varied within 3.18 - 3.54 Gy, depending on the end-point used for the assessment. DRCs were successfully validated in a biodosimetry exercise with uniform irradiation and PBI simulations in vitro and using in vivo data from four breast cancer patients after their first radiotherapy dose fraction.

Conclusions: Generating joint DRCs for ChA and ICS in a single experiment can be recommended as a rational methodology for laboratories practicing cytogenetic biodosimetry.

Purpose: Dr. Richard Hill performed pioneering work in the field of radiation-induced normal tissue injury to the lung including noninvasive imaging studies aimed at identifying imaging biomarkers of radiation-induced lung injury (RILI). RILI is a life-threatening toxicity of radiation exposure relevant to both cancer patients undergoing thoracic radiation therapy (RT) and victims of accidental radiation exposure. The ability to detect RILI noninvasively has the potential to guide treatment planning for RT and, in the case of victims of acute radiation exposures, inform the decision to start mitigative therapies. As part of this special issue of IJRB honoring Dr. Hill's many contributions to the field of radiation biology, this article reviews current advances in noninvasive imaging of RILI including computed tomography (CT), magnetic resonance (MR), hyperpolarized MR, nuclear medicine (PET and SPECT), and optical imaging with near-infrared (NIR) probes. Conclusion: The imaging modalities reviewed have potential to not only provide early identification of RILI but may also provide mechanistic insights into the progression of RILI via noninvasive detection of characteristic RILI mechanisms including: inflammation, vascular damage, cell death, oxidative stress, and fibrosis.

Purpose: Optimization of automated dicentric evaluation in the BIR laboratory is necessary to improve and accelerate individual biological dosimetry in radiation accident scenarios. Therefore, two different DCScore classifiers were analyzed for their suitability for use with laboratory-specific protocols, including two different lymphocyte culture conditions, 3-hour or 24-hour colcemid treatment.

Materials and methods: Dicentric formation was compared in 3 h and 24 h colcemid-treated cultures by fully- and semi-automated dicentric scoring using two different classifiers. Various calibration curves were constructed and absorbed doses of blinded X-irradiated blood samples were estimated after 24 h of colcemid treatment using both classifiers and scoring modes.

Results: 24 h colcemid treatment results in twice as many metaphases as 3 h colcemid treatment and the courses of dicentric frequencies after short- and long-term colcemid treatment differ, especially > 1 Gy. The "short-term colcemid classifier" detects more dicentric candidates and true positive dicentrics, respectively, especially > 2 Gy than the "long-term classifier" on the same slides.

Conclusion: Neither classifier was significantly better suited for the lab-specific MP preparations with regard to triage dose estimates for blinded samples by fully- as well as semi-automated analysis. For accurate dose assessment, it is recommended to adapt an available classifier to laboratory-specific conditions and protocols to optimize the identification of true dicentrics by DCScore.