Dosimetry and uncertainty approaches for the million person study of low-dose radiation health effects: overview of the recommendations in NCRP Report No. 178.

PURPOSE: Scientific Committee 6-9 was established by the National Council on Radiation Protection and Measurements (NCRP), charged to provide guidance in the derivation of organ doses and their uncertainty, and produced a report, NCRP Report No. 178, Deriving Organ Doses and their Uncertainty for Epidemiologic Studies with a focus on the Million Person Study of Low-Dose Radiation Health Effects (MPS). This review summarizes the conclusions and recommendations of NCRP Report No. 178, with a concentration on and overview of the dosimetry and uncertainty approaches for the cohorts in the MPS, along with guidelines regarding the essential approaches used to estimate organ doses and their uncertainties (from external and internal sources) within the framework of an epidemiologic study. CONCLUSIONS: The success of the MPS is tied to the validity of the dose reconstruction approaches to provide realistic estimates of organ-specific radiation absorbed doses that are as accurate and precise as possible and to properly evaluate their accompanying uncertainties. The dosimetry aspects for the MPS are challenging in that they address diverse exposure scenarios for diverse occupational groups being studied over a period of up to 70 y. Specific dosimetric reconstruction issues differ among the varied exposed populations that are considered: atomic veterans, U.S. Department of Energy workers exposed to both penetrating radiation and intakes of radionuclides, nuclear power plant workers, medical radiation workers, and industrial radiographers. While a major source of radiation exposure to the study population comes from external gamma- or x-ray sources, for some of the study groups, there is also a meaningful component of radionuclide intakes that requires internal radiation dosimetry assessments.

USTUR Special Session Roundtable-US Transuranium and Uranium Registries (USTUR): A Five-decade Follow-up of Plutonium and Uranium Workers.

The US Transuranium and Uranium Registries is a human tissue program that collects tissues posthumously from former nuclear workers and radiochemically analyzes them for actinides such as plutonium, americium, and uranium. It was established in 1968 with the goal of advancing science and improving the safety of future workers. Roundtable participants recalled various aspects of this multidisciplinary research program, from establishing consistent autopsy protocols to comparing the registries' findings to those of other programs, such as the historical beagle dog studies and the Russian Radiobiological Human Tissue Repository. The importance of meeting ethical and legal requirements, including written consent forms, was emphasized, as was the need to know whether workers were exposed to nonradiological hazards such as beryllium or asbestos. At Rocky Flats, a bioassay program was established to follow workers after they terminated employment. The resulting data continue to help researchers to improve the biokinetic models that are used to estimate intakes and radiation doses. After 50 y, the US Transuranium and Uranium Registries continues to contribute to our understanding of actinides in humans, which is a testament to the vision of its founders, the generosity of its tissue donors, and the many dedicated scientists who have worked together to achieve a common goal.

The Pseudo-Pelger huët Cell as a Retrospective Dosimeter: Analysis of a Radium Dial Painter Cohort.

Recently, the pseudo-Pelger Huët anomaly in peripheral blood neutrophils has been described as a new radiation-induced, stable biomarker. In this study, pseudo-Pelger Huët anomaly was examined in peripheral blood slides from a cohort of 166 former radium dial painters and ancillary personnel in the radium dial industry, 35 of whom had a marrow dose of zero above background. Members of the radium dial painter cohort ingested Ra and Ra at an early age (average age 20.6 ± 5.4 y; range 13-40 y) during the years 1914-1955. Exposure duration ranged from 1-1,820 wk with marrow dose 1.5-6,750 mGy. Pseudo-Pelger Huët anomaly expressed as a percentage of total neutrophils in this cohort rises in a sigmoidal fashion over five decades of red marrow dose. Six subjects in this cohort eventually developed malignancies: five osteosarcomas and one mastoid cell neoplasm. The pseudo-Pelger Huët anomaly percentage in these cases of neoplasm increases with marrow dose and is best fit with a sigmoid function, suggestive of a threshold effect. No sarcomas are seen for a marrow dose under 2 Gy. These results indicate that pseudo-Pelger Huët anomaly in peripheral blood is a reasonable surrogate for the estimation of alpha dose to bone marrow in historic radiation cases. Hypotheses are discussed to explain late (months to years), early (hours to days), and intermediate (weeks to months) effects of ionizing radiation, respectively, on the expression of genes encoding inner nuclear membrane proteins and their receptors, on the structure and function of nuclear membrane proteins and lipids, and on cytokinesis through chromatin bridge formation.

Rapid Response, Dose Assessment, and Clinical Management of a Plutonium-contaminated Puncture Wound.

Internalization of radionuclides occurs not only by inhalation, ingestion, parenteral injection (i.e., administration of radioactive material for a medical purpose), and direct transdermal absorption, but also by contaminated wounds. In June 2010, a glove-box operator at the U.S. Department of Energy's Savannah River Site sustained a puncture wound while venting canisters containing legacy materials contaminated with Pu. To indicate the canisters had been vented, a flag was inserted into the vent hole. The shaft of the flag penetrated the protective gloves worn by the operator. Initial monitoring performed with a zinc-sulfide alpha detector indicated 300 dpm at the wound site. After being cleared by radiological controls personnel, the patient was taken to the site medical facility where decontamination was attempted and diethylenetriaminepentaacetic acid (DTPA) was administered intravenously within 1.5 h of the incident. The patient was then taken to the Savannah River Site In Vivo Counting Facility where the wound was counted with a Canberra GL 2820 high-purity germanium detector, capable of quantifying contamination by detecting low-energy x rays and gamma rays. In addition to the classic 13, 17, and 20 keV photons associated with Pu, the low-yield (0.04%) 43.5 keV peak was also detected. This indicated a level of wound contamination orders of magnitude above the initial estimate of 300 dpm detected with handheld instrumentation. Trace quantities of Am were also identified via the 59.5 keV peak. A 24 h urine sample collection was begun on day 1 and continued at varying intervals for over a year. The patient underwent a punch biopsy at 3 h postincident (14,000 dpm removed) and excisional biopsies on days 1 and 9 (removal of an additional 3,200 dpm and 3,800 dpm, respectively). The initial post-DTPA urine sample analysis report indicated excretion in excess of 24,000 dpm Pu. Wound mapping was performed in an effort to determine migration from the wound site and indicated minimum local migration. In vivo counts were performed on the liver, axillary lymph nodes, supratrochlear lymph nodes, and skeleton to assess uptake and did not indicate measurable activity. Seventy-one total doses of DTPA were administered at varying frequencies for 317 d post intake. After allowing 100 d for removal of DTPA from the body, five 24 h urine samples were collected and analyzed for dose assessment by using the wound model described in National Council on Radiation Protection and Measurements Report No. 156. The total effective dose averted via physical removal of the contaminant and DTPA administration exceeded 1 Sv, demonstrating that rapid recognition of incident magnitude and prompt medical intervention are critical for dose aversion.

Thirteenth Annual Warren K. Sinclair Keynote Address: Where Are the Radiation Professionals (WARP)?

In July 2013, the National Council on Radiation Protection and Measurements convened a workshop for representatives from government, professional organizations, academia, and the private sector to discuss a potential shortage of radiation protection professionals in the not-too-distant future. This shortage manifests itself in declining membership of professional societies, decreasing enrollment in university programs in the radiological sciences, and perhaps most importantly, the imminent retirement of the largest birth cohort in American history, the so-called "baby boomer" generation. Consensus emerged that shortages already are, or soon will be, felt in government agencies (including state radiation control programs); membership in professional societies is declining precipitously; and student enrollments and university support for radiological disciplines are decreasing with no reversals expected. The supply of medical physicists appears to be adequate at least in the near term, although a shortage of available slots in accredited clinical training programs looms large. In general, the private sector appears stable, due in part to retirees joining the consultant ranks. However, it is clear that a severe problem exists with the lack of an adequate surge capacity to respond to a large-scale reactor accident or radiological terrorism attack in the United States. The workshop produced a number of recommendations, including increased funding of both fellowships and research in the radiological sciences, as well as creation of internships, practicums, and post-doctoral positions. A federal joint program support office that would more efficiently manage the careers of radiological professionals in the civil service would enhance recruiting and development, and increase the flexibility of the various agencies to manage their staffing needs.

Meeting the Needs of the Nation for Radiation Protection: Summary of the 52nd Annual Meeting of the National Council on Radiation Protection and Measurements.

The 52nd Annual Meeting of the National Council on Radiation Protection and Measurements (NCRP) was held in Bethesda, MD, 11-12 April 2016, on the topic of "Meeting National Needs for Radiation Protection." This meeting was an outgrowth of the NCRP initiative "Where are the Radiation Professionals?" (WARP), which addresses looming shortages in professional personnel trained in the radiological disciplines, including but not limited to health physics, radiological engineering, radiobiology, radiochemistry, radioecology, radiation emergency response; and the medical disciplines of diagnostic and interventional radiology, radiation oncology, nuclear medicine, and medical physics. A shortage of radiation professionals has been predicted for at least 20 y but now seems to be imminent. Obviously radiation professionals are needed for regulatory responsibilities at both state and federal levels, national defense, energy production, waste management, industrial applications, education, and medicine. Although the supply of radiation professionals in medicine appears to be adequate for the next decade or so, the use of radiation in medical diagnosis and therapy will continue to increase with the aging of the general population.

Core ethical values of radiological protection applied to Fukushima case: reflecting common morality and cultural diversities.

The International Commission on Radiological Protection (ICRP) has established Task Group 94 (TG94) to develop a publication to clarify the ethical foundations of the radiological protection system it recommends. This TG identified four core ethical values which structure the system: beneficence and non-maleficence, prudence, justice, and dignity. Since the ICRP is an international organization, its recommendations and guidance should be globally applicable and acceptable. Therefore, first this paper presents the basic principles of the ICRP radiological protection system and its core ethical values, along with a reflection on the variation of these values in Western and Eastern cultural traditions. Secondly, this paper reflects upon how these values can be applied in difficult ethical dilemmas as in the case of the emergency and post-accident phases of a nuclear power plant accident, using the Fukushima case to illustrate the challenges at stake. We found that the core ethical values underlying the ICRP system of radiological protection seem to be quite common throughout the world, although there are some variations among various cultural contexts. Especially we found that 'prudence' would call for somewhat different implementation in each cultural context, balancing and integrating sometime conflicting values, but always with objectives to achieve the well-being of people, which is itself the ultimate aim of the radiological protection system.

Dose reconstruction for the million worker study: status and guidelines.

The primary aim of the epidemiologic study of one million U.S. radiation workers and veterans [the Million Worker Study (MWS)] is to provide scientifically valid information on the level of radiation risk when exposures are received gradually over time and not within seconds, as was the case for Japanese atomic bomb survivors. The primary outcome of the epidemiologic study is cancer mortality, but other causes of death such as cardiovascular disease and cerebrovascular disease will be evaluated. The success of the study is tied to the validity of the dose reconstruction approaches to provide realistic estimates of organ-specific radiation absorbed doses that are as accurate and precise as possible and to properly evaluate their accompanying uncertainties. The dosimetry aspects for the MWS are challenging in that they address diverse exposure scenarios for diverse occupational groups being studied over a period of up to 70 y. The dosimetric issues differ among the varied exposed populations that are considered: atomic veterans, U.S. Department of Energy workers exposed to both penetrating radiation and intakes of radionuclides, nuclear power plant workers, medical radiation workers, and industrial radiographers. While a major source of radiation exposure to the study population comes from external gamma- or x-ray sources, for some of the study groups, there is a meaningful component of radionuclide intakes that requires internal radiation dosimetry assessments. Scientific Committee 6-9 has been established by the National Council on Radiation Protection and Measurements (NCRP) to produce a report on the comprehensive organ dose assessment (including uncertainty analysis) for the MWS. The NCRP dosimetry report will cover the specifics of practical dose reconstruction for the ongoing epidemiologic studies with uncertainty analysis discussions and will be a specific application of the guidance provided in NCRP Report Nos. 158, 163, 164, and 171. The main role of the Committee is to provide guidelines to the various groups of dosimetrists involved in the MWS to ensure that certain dosimetry criteria are considered: calculation of annual absorbed doses in the organs of interest, separation of low and high linear-energy transfer components, evaluation of uncertainties, and quality assurance and quality control. It is recognized that the MWS and its approaches to dosimetry are a work in progress and that there will be flexibility and changes in direction as new information is obtained with regard to both dosimetry and the epidemiologic features of the study components. This paper focuses on the description of the various components of the MWS, the available dosimetry results, and the challenges that have been encountered. It is expected that the Committee will complete its report in 2016.

Scientific issues in radiation dose reconstruction.

Stakeholders have raised numerous issues regarding the scientific basis of radiation dose reconstruction for compensation. These issues can be grouped into three broad categories: data issues, dosimetry issues, and compensation issues. Data issues include demographic data of the worker, changes in site operations over time (both production and exposure control), characterization of episodic vs. chronic exposures, and the use of coworker data. Dosimetry issues include methods for assessment of ambient exposures, missed dose, unmonitored dose, and medical x-ray dose incurred as a condition of employment. Specific issues related to external dose include the sensitivity, angular and energy dependence of personal monitors, exposure geometries, and the accompanying uncertainties. Those related to internal dose include sensitivity of bioassay methods, uncertainties in biokinetic models, appropriate dose coefficients, and modeling uncertainties. Compensation issues include uncertainties in the risk models and use of the 99th percentile of the distribution of probability of causation for awarding compensation. A review of the scientific literature and analysis of each of these issues distinguishes factors that play a major role in the compensation decision from those that do not.

The NCRP wound model: development and application.

The US National Council on Radiation Protection and Measurements, in collaboration with the International Commission on Radiological Protection, has been developing a biokinetic and dosimetric model for radionuclide-contaminated wounds. The finalised model is described briefly in this paper, together with the scientific basis and application. The multicompartment model uses first-order linear biokinetics to describe the retention and clearance of a radionuclide deposited in a wound site using seven default retention categories. Examples using plutonium nitrate in colloidal form and uranium in metal fragments show the behaviour of the less soluble forms of radionuclides in wounds, in which long-term retention is predicted. Using uranium as an example, the wound model is coupled to a uranium International Commission on Radiological Protection systemic model to predict urinary excretion patterns for different physicochemical forms of uranium. The latter application is needed for bioassay interpretation.

Radiation dose distributions in normal tissue adjacent to tumors containing (131)I or (90)Y: the potential for toxicity.

UNLABELLED: Given the relatively large tumor-absorbed doses reported for patients receiving radionuclide therapy, particularly radioimmunotherapy, and the relatively long pathlength of the nonpenetrating emissions of some radionuclides being used for these therapies, there exists the possibility of large absorbed doses to tissues adjacent to, surrounded by, or surrounding these tumors. Because tumors can occur adjacent to critical organs or tissues, such as arteries, nerves, pericardium, and the walls of the organs of the gastrointestinal tract, large absorbed doses to these normal tissues can lead to acute complications. METHODS: In this study, the Monte Carlo radiation transport code MCNP4b was used to simulate the deposition of energy from emissions of 2 radionuclides of interest, (131)I and (90)Y, to assess the possible magnitude of the absorbed doses in tissues adjacent to tumors. Mathematic models were constructed to simulate situations that might occur, such as tumor wrapped around a small cylinder (e.g., a nerve or artery), tumor against a tissue (e.g., the pericardium or wall of any gastrointestinal tract organ), and tumor surrounded by any soft tissue. Tumor masses of 10, 20, and 40 g were used in each model. Depth dose distributions were calculated using Monte Carlo simulations of the radiation transport in these geometric models. RESULTS: For tissues close to tumors containing (90)Y, the absorbed dose ranged from 24% of the absorbed dose in the tumor, for the case of tissues 1 mm from the tumor, to 103% of the absorbed dose in the tumor, for the case of small structures such as nerves or arteries surrounded by tumor. For tissues close to tumors containing (131)I, the absorbed dose ranged from 4% of the absorbed dose in the tumor, for the case of tissues 1 mm from the tumor, to 46% of the absorbed dose in the tumor, for the case of small structures such as nerves or arteries surrounded by tumor. CONCLUSION: This study showed that when absorbed doses to tumors are large, the absorbed dose to adjacent tissues can also be large, potentially causing unexpected toxicities.

Henri Jammet Memorial Lecture : The role of dosimetry in radiation accident response

This document explores the techniques of internal dosimetry, as well as radiation cytogenetics. Also it explains aspects about internal and external exposure accidents and some techniques to measure doses of radiation received such as decorporation therapym diuretics or simply increasing fluid intake may be used to increase the excretion rate of incorporated radioactive materials, adding another aspect to patient care. It mentions Prussian Blue used successfully in treating victims of the Goiania accident. In another part of the document explains investigations with biodosimetry: radiation cytogenetics