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PubMed2005

Dose reconstruction of a Brazilian industrial gamma radiography partial-body overexposure case.

In May 2000, an operator of a (60)Co industrial gamma radiography apparatus, during a routine service, was involved in a partial-body radiological accident, which caused serious injuries to his left hand. Dose reconstruction was started aiming to assess the radiation doses, in order to assist the medical staff in the evaluation and prescription of suitable medical procedures for the patient's treatment and follow-up. This work presents the dose reconstruction used for assessment of the distribution of doses on the patient's left hand, which was made using two methods: physical and computational techniques. For the first technique a physical hand simulator was built. The computational method was performed using microcomputer software for external dose calculations, named 'Visual Monte-Carlo-VMC', together with a hand voxel simulator. The values obtained through both methods for the distribution of absorbed doses on the operator's left hand were compared. About half of them were similar within a range of uncertainty of 20%.

Adult↗

PubMed2000

Dose reconstruction system for the exposed population living along the Techa River.

The Mayak Production Association, which began operation in 1948, was the first facility in the former Soviet Union for the production of plutonium. Significant worker and population exposure occurred as a result of failures in the technological processes in the late 1940's and early 1950's. Members of the public were exposed via discharge of about 1017 Bq of liquid wastes into the Techa River during 1949-1956, an explosion in the radioactive waste-storage facility in 1957, and gaseous aerosol releases within the first decades of the facility's operation. Residents of many villages downstream on the Techa River were exposed via a variety of pathways; the more significant included drinking of water from the river and external gamma exposure due to proximity to sediments and shoreline. The specific aim of this project is to enhance the reconstruction of external and internal radiation doses for individuals in the Extended Techa River Cohort. The purpose of this paper is to present the details of the methods that are being used in this enhanced dose-reconstruction effort and to provide example and representative results of the calculations. The methods of dose assessment currently being developed for the exposed population [termed the Techa River Dosimetry System-2000 (TRDS-2000)], which are a significant improvement on past methods (TRDS-1996), are presented. The new TRDS-2000 doses from the ingestion of radionuclides are substantially higher for the gastrointestinal tract, due to consideration of short-lived radionuclides. The TRDS-2000 doses from external exposure are substantially lower due to improvements in several factors. Assessment of uncertainty and validation of the "new" doses are significant issues currently under investigation.

Health Physics↗

PubMed2000

Current issues on EPR dose reconstruction in tooth enamel.

This paper focuses on the opportunities to gain risk assessment information from populations exposed to ionizing radiation. Details are presented on the scale of the nuclear events in several areas within the former Soviet Union. An overview of the issues associated with dose reconstruction by electron paramagnetic resonance (EPR) is given. Principles and outline of the EPR tooth enamel dose assessment are described. Technical details, the latest achievements and the problems of each procedural step are analyzed. In addition, the present accuracy of the EPR dose reconstruction, its problems and cost are discussed.

Dental Enamel↗

PubMed1996

An approach to dose reconstruction for the Urals population.

Population exposure in the Urals region occurred due to the releases of radionuclides by the Mayak plutonium facility in the 1950's. The major sources of radioactive contamination were the discharges of liquid wastes into the Techa river (1949-1956); an explosion in the storage facility for high level radioactive wastes which formed the East Urals Radioactive Trace in 1957; and gaseous aerosol releases within the first decade of the facility's operation (1949-1957). The problems of dose reconstruction for the population exposed on the Techa river banks and East Urals Radioactive Trace are outlined. The initial data sets and basic models for dose reconstruction are described. The main tasks of the Techa River Dosimetry System Project and the approaches to individual internal and external dose reassessment are formulated.

Humans↗

PubMed2003

Comparison of doses and risks obtained from dose reconstructions for historical operations of federal facilities that supported the development, production, or testing of nuclear weapons.

Five dose reconstruction projects focusing on historical public exposures from U.S. government nuclear facilities have been completed in the last 12 y (Fernald, Hanford, Nevada Test Site, Oak Ridge, Rocky Flats). Using information available in published reports, doses and excess health risks of the most serious contaminants in each study are compared for representative maximally and typically exposed individuals. For both the representative maximally exposed individual and the representative typically exposed individual, the highest excess risks of cancer incidence were from 131I released from Hanford, Nevada Test Site, and Oak Ridge and 222Rn released from Fernald (with central estimates for maximally exposed individuals approaching or exceeding 10(-2)); the lowest risks for both maximally and typically exposed individuals were from 239/240Pu and carbon tetrachloride released from Rocky Flats. Excess health risks to the representative maximally exposed individual were at or below 10(-40 for releases from Rocky Flats. For representative typically exposed individuals, the excess risks from releases of mixed radionuclides in the Clinch River (Oak Ridge), PCBs in East Fork Poplar Creek (Oak Ridge), and both plutonium and carbon tetrachloride released from Rocky Flats were mostly below 10(-5).

Air Pollutants, Radioactive↗

PubMed2000

EPR dose reconstruction for Russian nuclear workers.

The present paper describes results of the first independent evaluation of the accuracy of the dose-reconstruction technique by electron paramagnetic resonance using tooth enamel. Each of twenty-four teeth donated by Mayak nuclear workers with known occupational radiation exposure histories was cut into two parts so that each tooth could be shared for blind electron paramagnetic resonance examination by at least two of the four laboratories participating in the study. The mean difference (+/- SD) between electron paramagnetic resonance estimates of the paired samples of each tooth shared by the two laboratories in best agreement was 0.02 +/- 0.15 Gy. Mayak workers can be classified into two groups: modern workers (after 1961) having reliable official dose information and earlier nuclear workers whose dose information is less reliable because they were exposed mainly before 1961. Film badges did not contain filters until 1954. Doses in this earlier group are much higher (up to 5 Gy). Comparison of the electron paramagnetic resonance results with tooth doses calculated from official film-badge doses showed a close agreement for the first group, whereas in the second group, official doses appeared to be slightly higher than the electron paramagnetic resonance doses. The results suggested a possibility that the official doses were somewhat overestimated among the high-dose-exposed workers. Consequently, cancer risks derived from this high-dose group might tend to be slightly underestimated.

Electron Spin Resonance Spectroscopy↗

PubMed1998

Accidental intake of tritiated water: a cytogenetic follow-up case on translocation stability and dose reconstruction.

PURPOSE: To examine by fluorescence in situ hybridization (FISH) chromosomal translocations in a person who, 11 years previously, had accidentally incorporated tritiated water. To compare the resultant estimate of radiation dose with contemporary dosimetry made by urine analysis and dicentric chromosome scoring. MATERIALS AND METHODS: Blood lymphocytes were shared by two laboratories each performing the FISH analysis using different chromosome probe combinations. Doses were calculated by reference to an in vitro calibration curve produced in one of the laboratories. RESULTS: Good agreement in translocation yields was found by the two laboratories. Comparing the yields with the dicentric frequency obtained shortly after the accident and with a translocation frequency measured 6 years post exposure showed good agreement between all measurements. This indicates essentially perfect stability for translocations over an 11 year period in this individual. CONCLUSIONS: Dose reconstruction based on FISH-measured translocations showed good agreement with the dose estimated from initial dicentric measurements and from measurements of tritium in urine. Because of the extensive initial dosimetry performed on this individual, who received a uniform whole-body irradiation, the case serves as an excellent test for the use of FISH-measured translocations for retrospective biodosimetry.

Chromosomes, Human↗

PubMed2002

Dose reconstruction with electron paramagnetic resonance spectroscopy of deciduous teeth.

In the present study the feasibility of using whole, naturally loose deciduous incisors for dose reconstruction with electron paramagnetic resonance (EPR) spectroscopy was investigated. The properties of EPR signals were analysed before and after laboratory irradiation. The parameters of the native EPR signal of deciduous incisors was found to be different from those from enamel of permanent molars. The native EPR signal of deciduous incisors with peak-to-peak line width of 0.65 mT was located at g = 2.0050. The evaluated parameters of the dosimetric EPR signal (CO2-) of deciduous incisors were in agreement with those for enamel of permanent molars. A detection threshold for absorbed dose of about 100 mGy was estimated.

Child↗

PubMed2004

Dosimetric uncertainties of three-dimensional dose reconstruction from two-dimensional data in a multi-institutional study.

Inconsistencies in the treatment planning process leading to dosimetric uncertainties may affect conclusions drawn from interinstitutional radiation oncology clinical trials. The purpose of this study was to assess the dosimetric uncertainties resulting from the process of reconstructing three-dimensional dose distributions from two-dimensional treatment plan information provided by participating institutions in a randomized clinical trial. This study was based on American College of Radiology Protocol #427, Locally Advanced Multi-Modality Protocol; a multi-institutional phase II randomized study involving radiation therapy for patients with inoperable non-small cell lung cancer. Several sources of dosimetric uncertainty were identified and analyzed, including image quality of hard-copy computed tomography (CT) images, slice spacing of CT scans, treatment position, interpretations of target volumes by radiation oncologists, the contouring of normal anatomic structures, and the use of common beam models for all dose calculations. Each source of uncertainty was investigated using a set of plans, with the ideal characteristics of digital images with 3-mm axial slice spacing and a flat couch, consisting of eight cases from Vanderbilt University Medical Center with electronically transferred CT data. The target volume DVH values were dependent on the additional uncertainty introduced by differences in delineation of the target volumes by the participating radiation oncologists. The DVH values for the lungs and heart were dependent on image quality and treatment position. Esophagus DVH values were not dependent on any of the sources of uncertainty. None of the structure DVH values were dependent on slice thickness or variations in the contouring of normal anatomic structures. Reconstruction of three-dimensional dose distributions from two-dimensional treatment plan information may be useful in cases for which digital CT data is not available or for historical data review. However, dosimetric accuracy will depend on image quality of the treatment planning CT data and consistency in the delineation of tumor volumes.

Body Burden↗

PubMed1998

Retrospective dose reconstruction of human radiation exposure by FISH/chromosome painting.

Measurements of stable chromosomal aberrations by fluorescence in situ hybridisation (FISH)-chromosome painting has the potential to be used for dose reconstruction, years after exposure to ionising radiation. The method is, however, not yet fully standardised and validated. In particular, with respect to the limited lifespan of circulating T-lymphocytes, a level of uncertainty exists on the long-term persistence of stable aberrations. The main principles of the technique will be demonstrated. Based on results from the literature, the reliability and limitations are discussed.

Calibration↗

PubMed2002

Dose reconstruction in irradiated Fricke-agarose gels by means of MRI and optical techniques: 2D modelling of diffusion of ferric ions.

Fricke-agarose gels have elicited much interest in the field of radiation dosimetry, as tissue-equivalent dosemeters. magnetic resonance (MR) relaxation rates are measured for dose reconstruction. A major problem of Fricke-agarose gels is the diffusion of the ferric ions formed after irradiation. Knowledge of the diffusion coefficient of ferric ions may be necessary. Xylene orange, a dye that specifically chelates ferric ions, was added to the Fricke gel system to reduce ion diffusion and, as the binding gives a coloured complex, to allow optical detection of ferric ions. Diffusion of ferric ions in two dimensions and time evolution of ion concentration were evaluated. MR images were obtained at different times after irradiation. Ferric ion distribution, the corresponding images and the doses at different times after irradiation were reconstructed taking into account the calculated diffusion coefficients. Diffusion was then estimated by means of two different optical methods. The agreement obtained supports the reliability of the MRI method and of the model.

Gels↗

PubMed2001

A dose reconstruction of 60Co-contaminated window frames in a Taiwanese school.

Since 1992, hundreds of buildings in Taiwan were discovered to have 60Co contamination in the structural rebar. The contamination resulted from improper handling of 60Co-contaminated scrap metal in 1982 and 1983, which subsequently was recycled and used throughout Taiwan. Hsin-hsin Kindergarten school enrolled about 600 students over the 10-y period before the contamination was discovered. Hsin-hsin Kindergarten had three 60Co-contaminated steel window frames with measured dose rates on contact up to 150 microSv h(-1). In this study, a range of potential doses received by the Hsin-hsin Kindergarten students were estimated using ISOSHLD dose modeling software. ISOSHLD is a rapid, inexpensive screening tool to reconstruct dose ranges. To assess the potential risks to habitants of the school for the first year after construction, calculated dose rate ranges of 0.08 microSv h(-1) to 75.38 microSv h(-1) were then applied to the International Commission [corrected] on Radiation Protection 60 nominal detriment coefficients for stochastic effects. Risk estimates ranged from 1.46 x 10(-4) to 7.42 x 10(-4) excess fatal cancers per lifetime.

Adolescent↗

PubMed1997

Historical dose reconstruction project: estimating the population at risk.

This paper discusses methods used to estimate the size and location of the populations that lived around the Feed Materials Production Center near Ross, Ohio, from 1950 through 1990. This information will support an historical dose reconstruction for environmental exposures to radionuclides from this facility that is currently being done by the Centers for Disease Control and Prevention through a contract with Radiological Assessments Corporation. Available sources of data include (1) the U.S. Census, Ohio Township data; (2) the U.S. Census, Ohio Township block data; and (3) U.S. Geological Survey topographical maps that show structures. A distribution of age and sex is estimated that, together with population estimates, will provide information needed to estimate collective dose rates over time and to examine the feasibility of studying the relationship between exposure to radionuclides released from the Feed Materials Production Center and adverse health outcomes.

Animal Feed↗

PubMed2004

Genetic effects of radiotherapy for childhood cancer: gonadal dose reconstruction.

PURPOSE: To estimate the doses of radiation to organs of interest during treatment of childhood cancer for use in an epidemiologic study of possible heritable diseases, including birth defects, chromosomal abnormalities, cancer, stillbirth, and neonatal and premature death. METHODS AND MATERIALS: The study population was composed of more than 25,000 patients with cancer in Denmark and the United States who were survivors of childhood cancer and subsequently had nearly 6,500 children of their own. Radiation therapy records were sought for the survivors who parented offspring who had adverse pregnancy outcomes (>300 offspring), and for a sample of all survivors in a case-cohort design. The records were imaged and centrally abstracted. Water phantom measurements were made to estimate doses for a wide range of treatments. Mathematical phantoms were used to apply measured results to estimate doses to ovaries, uterus, testes, and pituitary for patients ranging in age from newborn to 25 years. Gonadal shielding, ovarian pinning (oophoropexy), and field blocking were taken into account. RESULTS: Testicular radiation doses ranged from <1 to 700 cGy (median, 7 cGy) and ovarian doses from <1 to >2,500 cGy (median, 13 cGy). Ten percent of the records were incomplete, but sufficient data were available for broad characterizations of gonadal dose. More than 49% of the gonadal doses were >10 cGy and 16% were >100 cGy. CONCLUSIONS: Sufficient radiation therapy data exist as far back as 1943 to enable computation of gonadal doses administered for curative therapy for childhood cancer. The range of gonadal doses is broad, and for many cancer survivors, is high and just below the threshold for infertility. Accordingly, the epidemiologic study has >90% power to detect a 1.3-fold risk of an adverse pregnancy outcome associated with radiation exposure to the gonads. This study should provide important information on the genetic consequences of radiation exposure to humans.

Adolescent↗

PubMed2006

Analysis of current assessments and perspectives of ESR tooth dosimetry for radiation dose reconstruction of the population residing near the Semipalatinsk nuclear test site.

Between 1949 and 1989 the Semipalatinsk nuclear test site (SNTS), an area of 19,000 square km in northeastern Kazakhstan, was the location of over 400 nuclear test explosions with a total explosive energy of 6.6 Mt TNT (trinitrotoluene or trotyl) equivalent. It is estimated that the bulk of the radiation exposure to the population resulted from three tests, conducted in 1949, 1951, and 1953 although estimations of radiation doses received by the local population have varied significantly. Analysis of the published ESR dose reconstruction results for residents of the villages near the SNTS show that they do not correlate well with other methods of dose assessment (e.g. model dose calculation and thermo luminescence dosimetry (TLD) in bricks). The most significant difference in dose estimations was found for the population of Dolon, which was exposed as result of the first Soviet nuclear test in 1949. Published results of ESR measurements in tooth enamel are considerably lower than other dose estimations. Detailed analysis of these results is provided and a possible explanation for this discrepancy and ways to eliminate it are suggested.

Adult↗

PubMed1997

Dose reconstruction for weapons experiments involving 140La at Los Alamos National Laboratory, 1944-1962.

A series of 254 weapons design experiments was conducted by Los Alamos National Laboratory from 1944 through 1962 and resulted in the dispersal of approximately 11 PBq (300 kCi) of radioactive 140La. All shots occurred at Point Able in Bayo Canyon, east of the Los Alamos townsite. Public interest and the Government Accounting Office probe precipitated a dose reconstruction to assess potential exposures to members of the public. The information available for each shot included explosive charge size, date and time of explosion, and shot activity. Detailed meteorological data were not available for the majority of the shots, requiring the development of statistically representative meteorological data. A wind rose was developed specific to the afternoon-evening time of the shots, and the wind frequency in each sector was used to determine the fraction of activity dispersed towards each hypothetical receptor. HOTSPOT 7, a Gaussian plume-based dispersion model, was used to determine the average dose per sector per unit of shot activity. The dose from penetrating radiation from ground-deposited 140La was greater by several orders of magnitude than the dose from inhalation and immersion. The highest doses to a permanent resident probably occurred in the easternmost part of the Los Alamos townsite. The highest annual dose occurred in 1955 and was approximately 0.23 mSv. Assuming an individual had been at the location of maximum potential exposure in the Los Alamos townsite continuously throughout the experiments, the total dose from the 18-y series would have been approximately 1.4 mSv with an average dose of approximately 0.09 mSv y(-1). Doses at nearby Totavi trailer park, San Ildefonso Pueblo, and Santa Clara Pueblo were approximately 75%, 40%, and 15%, respectively, of those at Los Alamos. Visitors to nearby public areas received negligible doses.

Environmental Exposure↗

PubMed2004

A computational tool based on voxel geometry for dose reconstruction of a radiological accident due to external exposure.

In the case of overexposure to ionising radiation, estimation of the absorbed dose in the organism is an important indicator for evaluating the biological consequences of this exposure. The physical dosimetry approach is based either on real reconstruction of the accident, using physical phantoms, or on calculation techniques. Tools using Monte Carlo simulations associated with geometric models are very powerful since they offer the possibility to simulate faithfully the victim and the environment for dose calculations in various accidental situations. Their work presents a new computational tool, called SESAME, dedicated to dose reconstruction of radiological accidents based on anthropomorphic voxel phantoms built from real medical images of the victim in association with the MCNP Monte Carlo code. The utility was, as a first step, validated for neutrons by experimental means using a physical tissue-equivalent phantom.

Algorithms↗

PubMed2001

Correction factors in the EPR dose reconstruction for residents of the Middle and Lower Techa riverside.

During 1949-1956, the first Soviet nuclear weapons plant, Mayak, released about 7.6 x 10(7) m(-3) of liquid radioactive waste with a total activity of 10(17) Bq into the Techa River (Southern Urals, Russia). 90Sr contributed 11.6% to the total waste radioactivity. As a result of these radioactive discharges, about 28,000 local residents were exposed to ionizing radiation, and some of them received relatively high doses. Internal exposure of the population residing at the Middle and Lower Techa riverside was mostly from 90Sr deposited in bone and tooth tissues. In order to reconstruct radiation doses to this population group, a study of 35 teeth extracted from local residents was carried out using electron paramagnetic resonance measurements. A total of 73 samples from these 35 teeth (tooth enamel, 33; crown dentin, 20; and root dentin, 20) were prepared and measured with electron paramagnetic resonance. The study revealed high doses (up to 15 Gy) absorbed in tooth enamel of the individuals born during 1945-1949, which was attributed to very high local 90Sr concentration in tooth enamel of this particular age group in the population. The analysis presented here takes into account (a) the time courses both of the release/intake of 90Sr and of the tooth formation, and (b) expected variations in measured absorbed doses due to differing geometric sizes of tooth structures. This methodology enables a more consistent picture to be developed of the 90Sr intake by the Middle and Lower Techa riverside population, based on electron paramagnetic resonance tooth dosimetry.

Age Factors↗