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Internal dosimetry in non-human biota is desirable from the viewpoint of radiation protection of the environment. The International Commission on Radiological Protection (ICRP) proposed Reference Animals and Plants using simplified models, such as ellipsoids and spheres and calculated absorbed fractions (AFs) for whole bodies. In this study, photon and electron AFs in whole bodies of voxel-based rat and frog models have been calculated and compared with AFs in the reference models. It was found that the voxel-based and the reference frog (or rat) models can be consistent for the whole-body AFs within a discrepancy of 25 %, as the source was uniformly distributed in the whole body. The specific absorbed fractions (SAFs) and S values were also evaluated in whole bodies and all organs of the voxel-based frog and rat models as the source was distributed in the whole body or skeleton. The results demonstrated that the whole-body SAFs reflect SAFs of all individual organs as the source was uniformly distributed per mass within the whole body by about 30 % uncertainties with exceptions for body contour (up to −40 %) for both electrons and photons due to enhanced radiation leakages, and for the skeleton for photons only (up to +185 %) due to differences in the mass attenuation coefficients. For nuclides such as 90Y and 90Sr, which were concentrated in the skeleton, there were large differences between S values in the whole body and those in individual organs, however the whole-body S values for the reference models with the whole body as the source were remarkably similar to those for the voxel-based models with the skeleton as the source, within about 4 and 0.3 %, respectively. It can be stated that whole-body SAFs or S values in simplified models without internal organs are not sufficient for accurate internal dosimetry because they do not reflect SAFs or S values of all individual organs as the source was not distributed uniformly in whole body. Thus, voxel-based models would be good candidates for dosimetry in non-human biota if further accuracy in environmental dosimetry is desired. [ABSTRACT FROM PUBLISHER]

Acetylation of lysine residues, one of the most common protein post-transcriptional modifications, is thought to regulate protein affinity with other proteins or nucleotides. Experimentally, the effects of acetylation have been studied using recombinant mutants in which lysine residues (K) are substituted with glutamine (Q) as a mimic of acetyl lysine (KQ mutant), or with arginine (R) as a mimic of nonacetylated lysine (KR mutant). These substitutions, however, have not been properly validated. The effects lysine acetylation on Ku, a multifunctional protein that has been primarily implicated in DNA repair and cell survival, are characterized herein using a series of computer simulations. The binding free energy was reduced in the KQ mutant, while the KR mutant had no effect, which is consistent with previous experimental results. Unexpectedly, the binding energy between Ku and DNA was maintained at almost the same level as in the wild type protein despite full acetylation of the lysine residues. These results suggest that the effects of acetylation may be overestimated when the KQ mutant is used as a mimic of the acetylated protein. © 2011 Wiley Periodicals, Inc. J Comput Chem 2012 [ABSTRACT FROM AUTHOR]

In the Japan Atomic Energy Agency, several studies have been conducted on the use of voxel models for internal dosimetry. Absorbed fractions (AFs) and S values have been evaluated for preclinical assessments of radiopharmaceuticals using human voxel models and a mouse voxel model. Computational calibration of in vivo measurement system has been also made using Japanese and Caucasian voxel models. In addition, for radiation protection of the environment, AFs have been evaluated using a frog voxel model. Each study was performed by using Monte Carlo simulations. Consequently, it was concluded that these data of Monte Carlo simulations and voxel models could adequately reproduce measurement results. Voxel models were found to be a significant tool for internal dosimetry since the models are anatomically realistic. This fact indicates that several studies on correction of the in vivo measurement efficiency for the variability of human subjects and interspecies scaling of organ doses will succeed. [ABSTRACT FROM PUBLISHER]

Radial energy deposition distribution, the distribution of DNA strand breaks and their yields were simulated by Monte Carlo track structure simulation for C and Ne ions with the same linear energy transfer (LET) around 450 keV/μm. The radial DNA damage distribution shows different pattern for C and Ne ions. Double strand break (DSB) are mostly formed in the central area, while the single strand break (SSB) tends to spread to the surrounding area. It is also shown that the production efficiency of the SSB and DSB depends on the radial distance. This result shows reasonable agreement with the recently obtained experimental observation, which indicates that different types of DNA damage shows different distribution patterns around C and Ne ion paths in cell nuclei. [ABSTRACT FROM PUBLISHER]

The internal exposures of the patients in nuclear medicine can be calculated based on the equations and data in ICRP Publications 53 and 80. Physical and biological parameters are used for the calculation, and both include uncertainties. Physical parameters can be considered as more precise than biological parameters, so that uncertainties originated from biological parameters are more important. Absorbed fractions (AFs) have been calculated by Monte-Carlo method using medical internal radiation dose (MIRD)-type mathematical phantoms. They depend on the shapes and sizes of the phantoms used in simulations. For estimating shape- and size-related uncertainties, AFs of pairs of source regions and target tissues of the patient-injected 99mTc-MDP were calculated by using EGS4 codes and a voxel phantom of Japanese male. By simply resizing the voxels of the phantom, the dependencies of size for AFs were calculated, and the uncertainties caused by the cumulated activities in source regions were also estimated by assuming these parameters distributions as Gaussian. [ABSTRACT FROM AUTHOR]

In recent years, concern has been raised about patient-specific doses due to the increased use of PET imaging. It is of scientific and practical interest for the accurate quantification of the doses to patients administered a radiopharmaceutical for PET imaging. In the present study, Monte Carlo simulations have been carried out to evaluate S values—the mean absorbed dose to the target region per unit cumulated activity in the source region—for positron emitters in the brain, heart and the urinary bladder content. The positron emitters considered were four radionuclides that are frequently used for PET imaging: 11C, 13N, 15O and 18F. S values were evaluated for the Medical Internal Radiation Dose S type mathematical phantom and the adult voxel phantoms developed at the Japan Atomic Energy Research Institute (JAERI). Consequently, Monte Carlo simulation and voxel phantoms were found to be useful in the evaluation of the beta dose to organs, in particular to hollow organs such as the urinary bladder. It was also demonstrated that the self-dose S values largely depend on the beta-ray energy and the mass of each target region. [ABSTRACT FROM AUTHOR]

In order to estimate residents’ external dose due to radionuclide exposure resulting from fallout deposit on the ground, the shielding and dose reduction effects provided by structures such as houses and workplaces are taken into account as most individuals spend a large portion of their time indoors. Many works on both calculation and measurement for European and American settlements have been reported and factors such as, shielding factors, protection factors, reduction factors, and location factors have been determined. However, measurement data for Japanese settlements are lacking. Thus, the Japanese government used reduction factors given in the International Atomic Energy Agency documents from American and European settlements when Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident occurred. The United Nations Scientific Committee on the Effects of Atomic Radiation used location factors from European settlements for the same reason. Soon after the FDNPP accident, several measurements and calculations were performed to obtain specific reduction factors for Japanese settlements due to this lack of data. This research reviews previous studies that determined factors such as, shielding factors, protection factors, reduction factors, and location factors and summarizes specific results for Japan. We discuss the issues in determining these factors and in applying them to estimate indoor dose. The contribution of surface contamination to the indoor ambient dose equivalent rate is also discussed. [ABSTRACT FROM AUTHOR]

In this study, we created integrated radiation air dose rate maps in the Fukushima region during 2011–2022 using airborne, car-borne, and walk surveys and fixed-location measurements. We applied a Bayesian geostatistical method to the 80 km radius of the Fukushima Daiichi Nuclear Power Plant and the entire Fukushima Prefecture while considering the history of the evacuation zone lifting in Fukushima. The integrated maps in this study fixed the bias to underestimate the air dose rates in forest areas and created integrated maps with a wider area and time series than previous studies. Furthermore, the results improved our understanding of the spatial heterogeneity of air dose rates. The correlations between walk and airborne surveys and walk and car-borne surveys changed over time (the walk survey includes fixed-location measurements), with the decreasing rates of air dose rate being faster for car-borne surveys, walk surveys, fixed-location measurements, and airborne surveys, in that order. The temporal changes in the variograms indicate that the heterogeneity of the radiocesium distribution in the environment varies with time due to decontamination activities and weathering effects. The trends inside and outside the evacuation zone differ. The temporal changes in the air dose rates from the integrated maps show a decrease between fixed-location measurements and the airborne survey. This decreasing rate mostly reflects the overall decrease in air dose rates. The results of this study could be used to evaluate detailed exposure doses to the public. [Display omitted] • Integrated radiation maps during 2011–2022 were created as representative maps. • Changes in the correlations among surveys were observed with time. • Changes in the variograms could depend on decontamination and weathering effects. • The maps will be valuable in evaluating exposure to humans in detail. [ABSTRACT FROM AUTHOR]

In order to estimate residents' external dose due to radionuclide exposure resulting from fallout deposit on the ground, the shielding and dose reduction effects provided by structures such as houses and workplaces are taken into account as most individuals spend a large portion of their time indoors. Many works on both calculation and measurement for European and American settlements have been reported and factors such as, shielding factors, protection factors, reduction factors, and location factors have been determined. However, measurement data for Japanese settlements are lacking. Thus, the Japanese government used reduction factors given in the International Atomic Energy Agency documents from American and European settlements when Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident occurred. The United Nations Scientific Committee on the Effects of Atomic Radiation used location factors from European settlements for the same reason. Soon after the FDNPP accident, several measurements and calculations were performed to obtain specific reduction factors for Japanese settlements due to this lack of data. This research reviews previous studies that determined factors such as, shielding factors, protection factors, reduction factors, and location factors and summarizes specific results for Japan. We discuss the issues in determining these factors and in applying them to estimate indoor dose. The contribution of surface contamination to the indoor ambient dose equivalent rate is also discussed. • Previous studies that determined reduction factors for European and American settlements are reviewed. • Specific results for Japan obtained after the Fukushima accident are summarized. • The issues in determining reduction factors and in applying them to estimate indoor dose are discussed. • The contribution of surface contamination to the indoor dose rate is discussed. [ABSTRACT FROM AUTHOR]

Abstract Following Fukushima nuclear disaster, several data gathering campaigns surveyed the radionuclide propagation in the environment. However, the acquired datasets do not have the same sampling dimension. For example, the airborne measurements are some sort of averaging over a circular field of view, beneath the sensor; while the soil analyses are much more punctual. The objective of this work is to compare the soil samples and an airborne survey to investigate whether these two datasets reflect the same spatial patterns or not. This is prerequisite for combining the multiresolution data to create and update the contamination map in a post-accidental situation. The analyses were performed on square tiles of 20 km side to study large- and small-dimension variations in 137Cs deposition. The former was modelled by fitting a plane (called trend) to the georeferenced data points; and the latter was modelled by computing the difference (called residual) between the trend and the initial data. Dip direction and dip angle of trends as well as minimum spatial correlation distance and anisotropy of residuals were computed for both the soil and airborne datasets and compared. Dip directions are compatible in 73% of the tiles and dip angles are generally close. Anisotropy directions are compatible in 49% of the tiles and minimum spatial correlation distances are significantly more marked for the airborne dataset. The soil samples and airborne measurements are therefore more in agreement in large-dimension (trend) rather than in small-dimension (residual) variations. More generally, both the datasets allow highlighting the main contamination plumes distinguishable because of high concentration values. The airborne dataset yet appears to be more powerful to quantify spatial correlations, which could be linked to the contamination mechanisms. Highlights • Soil analyses and airborne measurements are compared to each other. • In 47% of cases, both the datasets are compatible in small- and large-dimension variations. • Despite the general consistency of data, soil analyses are more heterogeneous. • Spatial-correlation within the variable could be a witness of hotspots in low-contaminated zones. [ABSTRACT FROM AUTHOR]

Abstract As part of the investigation of the distribution of ambient dose equivalent rates around the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), car-borne surveys using Kyoto University RAdiation MApping (KURAMA) systems have been conducted over a wide area in eastern Japan since 2011. The enormous volume of measurement data collected until 2016, including those until 2012 which were reported in the previous paper, was analyzed, and dependencies of the decreasing trend of the dose rates in regions within 80 km of the FDNPP on land-use categories, evacuation order areas and magnitude of the dose rates were examined. The air dose rates within 80 km of the FDNPP tended to decrease considerably with respect to the physical decay of radiocaesium. The decrease of the dose rate in the “forest” was slower than its decrease in other regions, while that in “urban area” was the fastest. The decrease in the air dose rate from 2011 was the fastest outside the evacuation order area until 2015, and it was the slowest in the “difficult-to-return zone”. However, the decreasing trend starting from 2013 showed that the decrease in the “zone in preparation for the lifting of the evacuation order” and in the “residence restriction area” was the fastest. It was found that the air dose rates decreased depending on the magnitude of the dose rates and elapsed time from the FDNPP accident, i.e. the decrease in air dose rates in areas with relatively low dose ranges (such as 0.2–0.5 μSv/h) was the largest during a period relatively early after the accident, and the decreasing rate in the dose rate ranges of 1.9–3.8 and 3.8–9.5 μSv/h were the fastest after 2013. The averaged ratios were analyzed to obtain the ecological half-lives of the fast and slow decay components, and those in whole area within 80 km of FDNPP were estimated to be 0.44 ± 0.05 y and 6.7 ± 1 y, respectively. The ecological half-lives with respect to the land use categories, evacuation order areas and magnitude of the dose rates were also evaluated. The decrease in the dose rates obtained by the car-borne survey was larger than that obtained on flat ground with few disturbances using the NaI(Tl) survey meter during approximately 1.5 y after the FDNPP accident. Thereafter, the difference of decreasing tendencies in the air dose rates between both the measurements was negligibly small, with the ratio of dose rates by the car-borne survey to those by the fixed-point measurement of 0.72–0.77. Highlights • Distribution maps and decreasing trend of dose rates in 5 y by car-borne surveys. • Ecological half-lives of the fast and slow components were estimated. • Dependencies of dose rates decreasing on evacuation order areas and dose rate ranges. • Comparison with the measurement on flat ground with few disturbances. [ABSTRACT FROM AUTHOR]

In this study, we quantify the temporal changes of air dose rates in the regional scale around the Fukushima Dai-ichi Nuclear Power Plant in Japan, and predict the spatial distribution of air dose rates in the future. We first apply the Bayesian geostatistical method developed by Wainwright et al. (2017) to integrate multiscale datasets including ground-based walk and car surveys, and airborne surveys, all of which have different scales, resolutions, spatial coverage, and accuracy. This method is based on geostatistics to represent spatial heterogeneous structures, and also on Bayesian hierarchical models to integrate multiscale, multi-type datasets in a consistent manner. We apply this method to the datasets from three years: 2014 to 2016. The temporal changes among the three integrated maps enables us to characterize the spatiotemporal dynamics of radiation air dose rates. The data-driven ecological decay model is then coupled with the integrated map to predict future dose rates. Results show that the air dose rates are decreasing consistently across the region. While slower in the forested region, the decrease is particularly significant in the town area. The decontamination has contributed to significant reduction of air dose rates. By 2026, the air dose rates will continue to decrease, and the area above 3.8 μSv/h will be almost fully contained within the non-residential forested zone. [ABSTRACT FROM AUTHOR]