PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Dose Reconstruction”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed2004

A radioecological model for thyroid dose reconstruction of the Belarus population following the Chernobyl accident.

A radioecological model was developed to estimate thyroid exposures of the Belarus population following the Chernobyl accident. The input of the model includes an extensive data set of the (137)Cs activity per unit area deposited during the Chernobyl accident, the rainfall data for different regions of Belarus, the (131)I/(137)Cs ratio in the deposit and the start of the grazing period in Belarus in April/May 1986. The output of the model is the age-dependent thyroid exposure due to the intake of (131)I with fresh milk. Age-dependent average thyroid doses were assessed for selected regions of Belarus. The maximum thyroid doses were estimated for the inhabitants of Gomel oblast where the highest deposition was observed among the regions considered here. The lowest doses were estimated for Vitebsk oblast with the lowest level of depositions. The mean exposures for the oblasts of Grodno, Minsk, Mogilev and Brest were very similar. The results were compared with estimations of thyroid exposure that were based on (131)I measurements in human thyroids, and they are in good agreement. The model may be used for the assessment of thyroid doses in Belarus for areas where no (131)I measurements are available.

Adult↗
PubMed2006

Effects of sunlight exposure on the human tooth enamel ESR spectra used for dose reconstruction.

The effects of solar radiation on the ESR signals in human tooth enamel were investigated. Enamel samples were exposed to the sunlight in Hiroshima, Japan, on sunny days for a total of about 228 hours over one year. The intensity of the illuminating sunlight was measured with a light meter, which then was converted to the intensity of the solar radiation. Three types of signals caused by the solar radiation were identified. The signal named S1 is identical to the gamma ray radiation-induced axially symmetrical signal and contains two signals S1( perpendicular) and S1(//) corresponding to the perpendicular and parallel components of the g-tensor characterized by g( perpendicular) = 2.0018 and g(//) = 1.9975 respectively. In addition, two other peaks named S2 and S3 are induced by the solar radiation. S2 is very near the inherent signal with g = 2.0052, possibly created by the same paramagnetic centers as the natural signal, and S3 is a weaker signal with g = 2.010. On increasing the amount of solar radiation S1 increases linearly, but S2 and S3 reach saturation. The average effect of the solar radiation on the S1( perpendicular) signal is estimated by dose equivalent gamma ray irradiation as 7.8 +/- 0.5 mGy (MJ m(-2))(-1), which corresponds to 19.6 +/- 1.3 mGy h(-1) at the latitude of Hiroshima. Signals S2 and S3 may be used to recognize the effect of solar radiation on the enamel.

Dental Enamel↗
PubMed2000

A radioiodine speciation, deposition, and dispersion model with uncertainty propagation for the Oak Ridge dose reconstruction.

Between 1944 and 1956, radioactive 131I was released into the atmosphere from operations at the Oak Ridge National Laboratory in Oak Ridge, TN. The releases occurred from stacks and from building vents and openings in three different chemical forms: elemental, organic, and particulate. During their transport in the atmosphere, different forms of iodine react differently with other atmospheric chemicals and moisture, and are removed from the plume at different rates by the processes of dry and wet deposition. A modified Gaussian plume model was developed to address the processes of radioiodine speciation, deposition, depletion, and dispersion in the atmosphere, and to propagate uncertainties in input parameter values through to the ground-level concentrations of 131I in air. A unique approach was used to develop an implicitly correlated set of hourly meteorological parameters for any day of a month for each month of the year from ten years of available data between 1987 and 1996. The model was validated for both annual average and short-term releases. For the annual average releases, the predictions of ground-level concentrations of 131I from the model were within a factor of 2 of measured field data. For two of the three sets of available weekly data, the measurements fell within the 95% subjective confidence interval of model predictions. Predictions of ground-level air concentrations were made on an annual average basis for the entire period of release and on a short-term, episodic basis for a 1954 accident.

Atmosphere↗
PubMed2001

Reconstruction of doses from radionuclide inhalation for nuclear power plant workers using air concentration measurements and associated uncertainties.

This paper presents a case study to illustrate the influence of parameter uncertainties on calculating an internal radiation dose of one actual nuclear plant worker, alias Mr. X, as well as the utility of air sampling for internal dose reconstruction. Input probability distributions for air concentrations of radionuclides were derived from empirical air measurements taken by fixed area air samplers. The total internal dose was calculated by multiplying radionuclide intake by dose conversion factors in Monte-Carlo simulations. There is significant variability in dose conversion factors and uncertainty in the estimated concentrations of radionuclides in the air to which Mr. X was exposed. The high variability and uncertainty of the model parameters contributed to large ranges of predicted internal doses for Mr. X. Two-dimensional Monte-Carlo simulations were conducted to separate contributions of the uncertainty and variability. Sensitivity analysis was conducted to determine which of the input parameters contributed most to uncertainty in internal dose estimates. Our analysis suggests that the uncertainty resulting from use of general air surveys contributes more to the internal dose ranges than the variability from DCFs and other population-derived parameters. Reduction of the uncertainty in reconstructed internal dose can be achieved by using personal air sampling and/or individual bioassays and regular whole-body counting.

Air Pollutants, Radioactive↗
PubMed1996

Scientific recommendations for the reconstruction of radiation doses due to the reactor accident at Chernobyl.

In the years after the Chernobyl reactor accident, many studies of the radiation exposure levels and resulting health effects in the countries of the CIS have been conducted. The increasing incidence of childhood thyroid cancers in Belarus and Ukraine has stimulated worldwide multi- and bilateral cooperations with those countries and Russia in order to optimize benefits for those directly affected, but also to enlarge current knowledge of the consequences of reactor accidents. An international workshop on dose reconstruction was held in Bad Honnef, June 6 to 9, 1994, to address the problems which arise in dose reconstruction. The main objectives of this workshop were to bring together the best professional expertise and scientific knowledge and to achieve a better, multi-disciplinary harmonisation of the different scientific approaches. After intensive discussions the participants of this workshop formulated the following scientific recommendations for radiation dose reconstruction.

Body Burden↗
PubMedDate not supplied

[The use of the FISH method for reconstructing the absorbed doses received by participants in the clean-up of the accident at the Chernobyl Atomic Electric Power Station].

The frequency of stable translocations using two-color fluorescence in situ hybridisation (FISH) were determined in peripheral blood lymphocytes of 20 persons who took part in liquidation of the Chernobyl accident and of 11 persons of control group. The individual doses for all patients were estimated from a calibration dose-response curve for stable translocation. The doses estimated by our cytogenetic data not always coincided with official dosimetric data. The possibility of using FISH for dose reconstruction of past radiation exposure was discussed.

Adult↗
PubMed2006

Lessons of the 3rd international intercomparison on EPR dosimetry with teeth: similarities and differences of two successful techniques.

Despite the considerable improvement in accuracy in comparison with previous intercomparison programmes, the outcome of the recent 3rd International Intercomparison on EPR Tooth Dosimetry has demonstrated that performance of various protocols practised in different laboratories significantly varies. SCRM and MUG took part in this intercomparison with their own versions of EPR dosimetry protocols, demonstrating the good correlation between reconstructed and nominal doses (best result for SCRM and fourth best for MUG) and the lowest both absolute and relative mean deviations from the nominal doses. Although the general results of the 3rd Intercomparison are being discussed elsewhere in this issue by Wieser et al., this presentation is focused on the discussion of the common features of the two techniques, which may have an effect on good performance in dose reconstruction. In addition to the mthods of analysis of the intercomparison results, as used in Wieser et al., SCRM and MUG studied the influence of an additional factor--the selection of the standard of the native signal--on the quality of the dose reconstruction.

Dose-Response Relationship, Radiation↗
PubMed1996

Radiation doses from Hanford Site releases to the atmosphere and the Columbia River.

Radiation doses to individuals were estimated for the years 1944-1992 as part of the Hanford Dose Reconstruction Project (HEDR). The dose estimates were based on the radioactive releases to the atmosphere and Columbia River from the Hanford Site in southcentral Washington State. Conceptual models, computer codes, and previously published dose estimates were used to reconstruct doses. The most significant exposure pathway was found to be the consumption of cow's milk containing 131I. The median cumulative dose estimates to the thyroid of children ranged from < 0.7 mGy to 2.3 Gy throughout the study area, depending upon residence location. The highest estimated cumulative dose to a child ranged from 0.6-8.4 Gy (5th and 95th percentiles) with a median of 2.3 Gy based on 100 Monte Carlo realizations. The geographic distribution of the dose levels was directly related to the pattern of 131I deposition and was affected by the distribution of commercial milk and leafy vegetables. For the atmospheric pathway, the highest cumulative effective dose equivalent to an adult was estimated to be 12 mSv at Ringold, Washington, for the period 1944-1992. For the Columbia River pathway, cumulative effective dose equivalent estimates ranged from < 5 mSv to 15 mSv cumulative dose to maximally exposed adults downriver from the Hanford Site for the years 1944-1992. The most significant river exposure pathway was consumption of resident fish containing 32P and 65Zn.

Adult↗
PubMed2001

Determination of the accuracy of implant reconstruction and dose delivery in brachytherapy in The Netherlands and Belgium.

PURPOSE: To gain insight into the accuracy of brachytherapy treatments, the accuracy of implant reconstruction and dose delivery was investigated in 33 radiotherapy institutions in The Netherlands and Belgium. MATERIALS AND METHODS: The accuracy of the implant reconstruction method was determined using a cubic phantom containing 25 spheres at well-known positions. Reconstruction measurements were obtained on 41 brachytherapy localizers, 33 of which were simulators. The reconstructed distances between the spheres were compared with the true distances. The accuracy of the dose delivery was determined for high dose rate (HDR), pulsed dose rate (PDR) and low dose rate (LDR) afterloading systems using a polymethyl methacrylate cylindrical phantom containing a NE 2571 ionization chamber in its centre. The institutions were asked to deliver a prescribed dose at the centre of the phantom. The measured dose was compared with the prescribed dose. RESULTS: The average reconstruction accuracy was -0.07 mm (+/-0.4 mm, 1 SD) for 41 localizers. The average deviation of the measured dose from the prescribed dose was +0.9% (+/-1.3%, 1 SD) for 21 HDR afterloading systems, +1.0% (+/-2.3%, 1 SD) for 12 PDR afterloaders, and +1.8% (+/-2.5%, 1 SD) for 15 LDR afterloaders. CONCLUSIONS: This comparison showed a good accuracy of brachytherapy implant reconstruction and dose delivery in The Netherlands and Belgium.

Belgium↗
PubMedDate not supplied

Verification of occupational doses at the first nuclear plant in the former Soviet Union.

Mean annual occupational exposures are reported for radiation workers at the first Russian industrial nuclear facility 'Mayak', South Ural region, for the period 1948-1988. The underlying individual doses originate from the register of the in-plant radiation safety department and are based on local film dosimetry results. Differentiation is made between personnel working at reactor and radiochemical processing plants. Verification of summed film doses is performed by means of ESR dose reconstruction using extracted teeth from selected individuals. Explanations are given for observed discrepancies between the reconstructed individual doses and original integrated film dosimetry results. The research potential of combined dose information from specific tooth enamel and dentine are shown.

Dental Enamel↗
PubMed2001

EPR tooth enamel dosimetry: optimization of the automated spectra deconvolution routine.

A computer routine was developed for automatic deconvolution of electron paramagnetic resonance spectra of tooth enamel samples for individual radiation dose reconstruction in the low dose region. The deconvolution routine uses the non-linear least square fit of a model simulating a tooth enamel spectrum by superposition of derivative Gaussian functions to obtain the amplitude of the dosimetric radiation induced signal. The parameters of the model and of the routine were optimized on a dose response level using a criterion of the least standard deviation of the derived radiation induced signal amplitude from the regression line vs. the nominal doses for the series of spectra of samples irradiated in known doses in the range 0-500 mGy. It was found that for the series of spectra of the heterogeneous samples (every sample is prepared from different teeth of different persons), it is essential to vary in the least square fit the parameters describing the shape of the native background signal in order to obtain the best accuracy. In the case of the series of spectra of the homogeneous (pooled) samples, almost the same accuracy of the results was obtained using the procedures with varied and fixed background signal parameters. The standard error of the dose reconstruction by the optimized deconvolution procedure was estimated as about 30 mGy for heterogeneous samples and 20 mGy for homogeneous samples.

Algorithms↗
PubMed2002

Cancer incidence and risk estimation among medical x-ray workers in China, 1950-1995.

Cancer incidence (1950-1995) among 27,011 medical diagnostic x-ray workers was compared by means of O/E system with that of 25,782 other medical specialists employed between 1950 and 1980 to provide evidence of human malignant tumors produced by protracted and fractionated exposure to ionizing radiation and to assess resultant cancer risk. Significant cancer risk was seen among diagnostic x-ray workers (RR = 1.2, 95% CI: 1.1-1.3). Significantly elevated risks were found for leukemia and cancers of skin, female breast, lung, liver, bladder, and esophagus; the RRs were 2.2, 4.1, 1.3, 1.2, 1.2, 1.8, and 2.7, respectively. The patterns of risk associated with years since beginning x-ray work and with age and calendar year of initial employment suggest that the excesses of leukemia, skin cancer, and female breast cancer-and possibly thyroid cancer-were related to occupational exposure to x rays. Because of a lack of individual dosimetry for Chinese medical x-ray workers (CMXW) before 1985, the dose was reconstructed by physical and biological retrospective dosimetry methods. The cancer risk of CMXW was estimated based on the reconstructed dose. The average cumulative dose for the earlier cohort (employed before 1970) was 551 mGy, and for the later cohort (employed from 1970 to 1980) it was 82 mGy. The RRs of leukemia and solid cancer were significantly high for the earlier cohort: 2.4 for leukemia, 1.2 for solid cancer. But no significant increase of RR was evident for the later cohort. The RR of leukemia was 1.7 and 1.1 for solid cancer. This means a significant cancer risk can be induced by long term fractionated exposure to ionizing radiation when the cumulative dose reaches a certain level.

Adult↗
PubMed2000

The assessment of radiation exposures in Native American communities from nuclear weapons testing in Nevada.

Native Americans residing in a broad region downwind from the Nevada Test Site during the 1950s and 1960s received significant radiation exposures from nuclear weapons testing. Because of differences in diet, activities, and housing, their radiation exposures are only very imperfectly represented in the Department of Energy dose reconstructions. There are important missing pathways, including exposures to radioactive iodine from eating small game. The dose reconstruction model assumptions about cattle feeding practices across a year are unlikely to apply to the native communities as are other model assumptions about diet. Thus exposures from drinking milk and eating vegetables have not yet been properly estimated for these communities. Through consultations with members of the affected communities, these deficiencies could be corrected and the dose reconstruction extended to Native Americans. An illustration of the feasibility of extending the dose reconstruction is provided by a sample calculation to estimate radiation exposures to the thyroid from eating radio-iodine-contaminated rabbit thyroids after the Sedan test. The illustration is continued with a discussion of how the calculation results may be used to make estimates for other tests and other locations.

Adolescent↗
PubMed1996

Identification and screening evaluation of key historical materials and emission sources at the Oak Ridge Reservation.

In 1991, the State of Tennessee initiated a Health Studies Agreement with the U.S. Department of Energy. It included independent studies of possible adverse health effects in people living near the Oak Ridge Reservation resulting from releases of chemicals and radionuclides since 1942. A Dose Reconstruction Feasibility, the first of a planned sequence of initiatives to evaluate the potential for health effects, included application of screening methods to focus subsequent dose reconstruction and epidemiologic efforts on the materials and emission sources that have historically been most important. The feasibility study produced a history of operations that likely generated off-site releases from the X-10, K-25, Y-12, and S-50 plants, based on reviews of classified and unclassified records and interviews of active and retired workers. The availability of environmental monitoring and research data that would support dose reconstruction was also characterized. Quantitative emission and environmental contamination data were used to identify those materials and plant activities that should receive the highest priority in further health studies. Plausible exposure pathways were identified, and screening methods were used to identify the most important pathways and past activities that appear to be associated with the greatest health hazards. The materials and activities shown to have the highest potential for public health hazards are as follows: 1) The release of radioiodine [likely over 3.7 PBq (100,000 Ci)] to the air from radioactive lanthanum ("RaLa") processing at X-10 (now Oak Ridge National Laboratory) from 1944 through 1956; 2) The release of 137Cs and other radionuclides in liquid wastes from chemical separation activities at X-10; 3) The release of mercury to the air, soil, and surface waters from Y-12 lithium enrichment operations between 1950 and 1963. About 11,000,000 kg of mercury were handled at Y-12, and 910,000 kg were reported lost or unaccounted for; and 4) The release of polychlorinated biphenyls (PCBs) from machining oils, electrical equipment, and other sources in the Oak Ridge area. Based on the findings of the study, the Oak Ridge Health Agreement Steering Panel called for a dose reconstruction for radioiodine, mercury, PCBs, and radionuclides released from White Oak Creek and research into opportunities for analytic epidemiologic studies to identify adverse health effects in exposed populations.

Air Pollutants, Radioactive↗
PubMed1998

Maximum likelihood as a common computational framework in tomotherapy.

Tomotherapy is a dose delivery technique using helical or axial intensity modulated beams. One of the strengths of the tomotherapy concept is that it can incorporate a number of processes into a single piece of equipment. These processes include treatment optimization planning, dose reconstruction and kilovoltage/megavoltage image reconstruction. A common computational technique that could be used for all of these processes would be very appealing. The maximum likelihood estimator, originally developed for emission tomography, can serve as a useful tool in imaging and radiotherapy. We believe that this approach can play an important role in the processes of optimization planning, dose reconstruction and kilovoltage and/or megavoltage image reconstruction. These processes involve computations that require comparable physical methods. They are also based on equivalent assumptions, and they have similar mathematical solutions. As a result, the maximum likelihood approach is able to provide a common framework for all three of these computational problems. We will demonstrate how maximum likelihood methods can be applied to optimization planning, dose reconstruction and megavoltage image reconstruction in tomotherapy. Results for planning optimization, dose reconstruction and megavoltage image reconstruction will be presented. Strengths and weaknesses of the methodology are analysed. Future directions for this work are also suggested.

Algorithms↗
PubMed2005

Testing prediction capabilities of an 131I terrestrial transport model by using measurements collected at the Hanford nuclear facility.

A model describing transport of 131I in the environment was developed by SENES Oak Ridge, Inc., for assessment of radiation doses and excess lifetime risk from 131I atmospheric releases from Oak Ridge Reservation in Oak Ridge, Tennessee, and from Idaho National Engineering and Environmental Laboratory in southeast Idaho. This paper describes the results of an exercise designed to test the reliability of this model and to identify the main sources of uncertainty in doses and risks estimated by this model. The testing of the model was based on materials published by the International Atomic Energy Agency BIOMASS program, specifically environmental data collected after the release into atmosphere of 63 curies of 131I during 2-5 September 1963, after an accident at the Hanford PUREX Chemical Separations Plant, in Hanford, Washington. Measurements of activity in air, vegetation, and milk were collected in nine counties around Hanford during the first couple of months after the accident. The activity of 131I in the thyroid glands of two children was measured 47 d after the accident. The model developed by SENES Oak Ridge, Inc., was used to estimate concentrations of 131I in environmental media, thyroid doses for the general population, and the activity of 131I in thyroid glands of the two children. Predicted concentrations of 131I in pasture grass and milk and thyroid doses were compared with similar estimates produced by other modelers. The SENES model was also used to estimate excess lifetime risk of thyroid cancer due to the September 1963 releases of 131I from Hanford. The SENES model was first calibrated and then applied to all locations of interest around Hanford without fitting the model parameters to a given location. Predictions showed that the SENES model reproduces satisfactorily the time-dependent and the time-integrated measured concentrations in vegetation and milk, and provides reliable estimates of 131I activity in thyroids of children. SENES model generated concentrations of 131I closer to observed concentrations, as compared to the predictions produced with other models. The inter-model comparison showed that variation of thyroid doses among all participating models (SENES model included) was a factor of 3 for the general population, but a factor of 10 for the two studied children. As opposed to other models, SENES model allows a complete analysis of uncertainties in every predicted quantity, including estimated thyroid doses and risk of thyroid cancer. The uncertainties in the risk-per-unit-dose and the dose-per-unit-intake coefficients are major contributors to the uncertainty in the estimated lifetime risk and thyroid dose, respectively. The largest contributors to the uncertainty in the estimated concentration in milk are the feed-to-milk transfer factor (F(m)), the dry deposition velocity (V(d)), and the mass interception factor (r/Y)dry for the elemental form of iodine (I2). Exposure to the 1963 PUREX/Hanford accident produced low doses and risks for people living at the studied locations. The upper 97.5th percentile of the excess lifetime risk of thyroid cancer for the most extreme situations is about 10(-4). Measurements in pasture grass and milk at all locations around Hanford indicate a very low transfer of 131I from pasture to cow's milk (e.g., a feed-to-milk transfer coefficient, F(m), for commercial cows of about 0.0022 d L(-1)). These values are towards the low end of F(m) values measured elsewhere and they are low compared to the F(m) values used in other dose reconstruction studies, including the Hanford Environmental Dose Reconstruction.

Adolescent↗