Parameter uncertainty analysis of the equivalent lung dose coefficient for the intake of radon in mines: A review.

Radon presents significant health risks due to its short-lived progeny. The evaluation of the equivalent lung dose coefficient is crucial for assessing the potential health effects of radon exposure. This review focuses on the uncertainty analysis of the parameters associated with the calculation of the equivalent lung dose coefficient attributed to radon inhalation in mines. This analysis is complex due to various factors, such as geological conditions, ventilation rates, and occupational practices. The literature review systematically examines the sources of radon and its health effects among underground miners. It also discusses the human respiratory tract model used to calculate the equivalent lung dose coefficient and the associated parameters leading to uncertainties in the calculated lung dose. Additionally, the review covers the different methodologies employed for uncertainty quantification and their implications on dose assessment. The text discusses challenges and limitations in current research practices and provides recommendations for future studies. Accurate risk assessment and effective safety measures in mining environments require understanding and mitigating parameter uncertainties.

CADORmed: a tool for internal dose assessment.

CADORmed is a free bespoke Excel® tool for committed effective dose assessment using latest dose coefficients from ICRP OIR publications. The field of application of CADORmed is special monitoring, and it is not available for the dose assessment of chronic exposure. Calculations are made according to EURADOS guidelines and principles (EURADOS report 2013-1). The Chi-squared test for the goodness of fit is made with a scattering factor for type A and type B errors according to the EURADOS report. The Intake is calculated with the maximum likelihood method. Measurements that are below the detection limit are incorporated by the use of an allocated value equal to one-half or one-quarter of the detection limit. The Identification of rogue data can easily be achieved. Advanced options may also be used: mixed ingestion and inhalation, mixture of default absorption types, correction for DTPA treatment, calculation with a new intake and adjustment when the date of intake are unknown. The validation of the tool has been included in the work plan of EURADOS WG 7. The validation plan has been defined and the validation tests completed. All changes are traced in a Quality Assurance document.

Ustur Case 0846: Modeling Americium Biokinetics after Intensive Decorporation Therapy.

Decorporation therapy with salts of diethylenetriamine-pentaacetic acid binds actinides, thereby limiting uptake to organs and enhancing the rate at which actinides are excreted in urine. International Commission on Radiological Protection reference biokinetic models cannot be used to fit this enhanced exertion simultaneously with the baseline actinide excretion rate that is observed prior to the start of therapy and/or after the effects of therapy have ceased. In this study, the Coordinated Network on Radiation Dosimetry approach, which was initially developed for modeling decorporation of plutonium, was applied to model decorporation of americium using data from a former radiation worker who agreed to donate his body to the US Transuranium and Uranium Registries for research. This individual was exposed to airborne Am, resulting in a total-body activity of 66.6 kBq. He was treated with calcium-diethylenetriamine-pentaacetic acid for 7 y. The time and duration of intakes are unknown as no incident reports are available. Modeling of different assumptions showed that an acute intake of 5-µm activity median aerodynamic diameter type M aerosols provides the most reasonable description of the available pretherapeutic data; however, the observed Am activity in the lungs at the time of death was higher than the one predicted for type M material. The Coordinated Network on Radiation Dosimetry approach for decorporation modeling was used to model the in vivo chelation process directly. It was found that the Coordinated Network on Radiation Dosimetry approach, which only considered chelation in blood and extracellular fluids, underestimated the urinary excretion of Am during diethylenetriamine-pentaacetic acid treatment; therefore, the approach was extended to include chelation in the liver. Both urinary excretion and whole-body retention could be described when it was assumed that 25% of chelation occurred in the liver, 75% occurred in the blood and ST0 compartment, and the chelation rate constant was 1 × 10 pmol d. It was observed that enhancement of urinary excretion of Am after injection of diethylenetriamine-pentaacetic acid exponentially decreased to the baseline level with an average half-time of 2.2 ± 0.7 d.

30-y follow-up of a Pu/Am inhalation case.

In 1983, a young man inhaled accidentally a large amount of plutonium and americium. This case was carefully followed until 2013. Since no decorporation measures had been taken, the undisturbed metabolism of Pu and Am can be derived from the data. First objective was to determine the amount of inhaled radionuclides and to estimate committed effective dose. In vivo and excretion measurements started immediately after the inhalation, and for quality assurance, all types of measurements were performed by different labs in Europe and the USA. After dose assessment by various international groups were completed, the measurements were continued to produce scientific data for model validation. The data have been analysed here to estimate lung absorption parameter values for the inhaled plutonium and americium oxide using the proposed new ICRP Human Respiratory Tract Model. As supplement to the biokinetic modelling, biological data from three different cytogenetic markers have been added. The estimated committed effective dose is in the order of 1 Sv. The subject is 30 y after the inhalation, of good health, according to a recent medical check-up.

[Calibration of a whole body counter using Monte Carlo methods]. / Kalibration eines Ganzkörperzählers mit Monte-Carlo-Methoden.

Radioactive substances in the human body can be identified and quantified by gamma spectroscopy using whole body counters. Counting efficiencies needed for calculation of incorporated activities are generally determined from measurements of phantoms simulating shape and density of a human and filled with known activity concentrations. The Cologne whole body counter setup was simulated using the EGSnrc Monte Carlo code system. The simulations did reproduce the spectra and efficiencies from phantom measurements (within +/- 2% for K-40). Variations of the phantom position alongside the stretcher resulted in parabola-shaped courses with efficiency changes of up to 5%. Nuclides which are inaccessible to phantom measurements can be quantified by weighted summation of efficiencies generatedfrom simulation offictitious monoenergetic gamma emitters. For I-131, a strong dependence upon the activity distribution inside the body was observed in simulations with a simplified model of the human body Inclusion of the skeleton in the model had a rather small effect. The efficiency decreases linearly with body length by up to 6% when body mass is kept constant. This has to be taken into account when the activity needs to be determined with high precision. For in vivo counting in the context of radiation protection, however, efficiencies can be deduced with sufficient accuracy from measurements or simulations of simple phantoms.

Developing a physiologically based approach for modeling plutonium decorporation therapy with DTPA.

PURPOSE: To develop a physiologically based compartmental approach for modeling plutonium decorporation therapy with the chelating agent Diethylenetriaminepentaacetic acid (Ca-DTPA/Zn-DTPA). MATERIALS AND METHODS: Model calculations were performed using the software package SAAM II (©The Epsilon Group, Charlottesville, Virginia, USA). The Luciani/Polig compartmental model with age-dependent description of the bone recycling processes was used for the biokinetics of plutonium. RESULTS: The Luciani/Polig model was slightly modified in order to account for the speciation of plutonium in blood and for the different affinities for DTPA of the present chemical species. The introduction of two separate blood compartments, describing low-molecular-weight complexes of plutonium (Pu-LW) and transferrin-bound plutonium (Pu-Tf), respectively, and one additional compartment describing plutonium in the interstitial fluids was performed successfully. CONCLUSIONS: The next step of the work is the modeling of the chelation process, coupling the physiologically modified structure with the biokinetic model for DTPA. RESULTS of animal studies performed under controlled conditions will enable to better understand the principles of the involved mechanisms.

Voxel2MCNP: a framework for modeling, simulation and evaluation of radiation transport scenarios for Monte Carlo codes.

The basic idea of Voxel2MCNP is to provide a framework supporting users in modeling radiation transport scenarios using voxel phantoms and other geometric models, generating corresponding input for the Monte Carlo code MCNPX, and evaluating simulation output. Applications at Karlsruhe Institute of Technology are primarily whole and partial body counter calibration and calculation of dose conversion coefficients. A new generic data model describing data related to radiation transport, including phantom and detector geometries and their properties, sources, tallies and materials, has been developed. It is modular and generally independent of the targeted Monte Carlo code. The data model has been implemented as an XML-based file format to facilitate data exchange, and integrated with Voxel2MCNP to provide a common interface for modeling, visualization, and evaluation of data. Also, extensions to allow compatibility with several file formats, such as ENSDF for nuclear structure properties and radioactive decay data, SimpleGeo for solid geometry modeling, ImageJ for voxel lattices, and MCNPX's MCTAL for simulation results have been added. The framework is presented and discussed in this paper and example workflows for body counter calibration and calculation of dose conversion coefficients is given to illustrate its application.

A new position recording system for the partial-body counter at KIT.

The position of detectors used for partial-body counters relative to a measured person has considerable influence on the counting efficiency of low-energy photon emitters. To minimise reading errors and enhance reproducibility of position data, an electronic position recording system was installed in the partial-body counter chamber at KIT. Phoswich detectors have been equipped with electronic sensors to determine the position and axes of the detectors. Additionally, a laser measurement system determines the position of arbitrary landmarks, e.g. point sources, anatomical features of phantoms and test persons. A network interface enables the reading of the position data on any connected computer. The system was successfully used to validate Monte Carlo simulations of partial-body counting scenarios for the numerical determination of counting efficiencies.

Analysis of the variability of biokinetic model parameters due to inter-individual variation.

Biokinetic models for the assessment of individual internal doses represent the physiological processes of a standardized human, which affect the internal distribution of the radionuclide of interest. The flow from one compartment into another is specified by transfer rates, which may vary from person to person. The rate constants are then representing the mean values for the population as a whole, around which individual parameters fluctuate according to given probability densities. Analytical distribution propagation can be calculated only for very simple models. The influence of inter-individual variation can be studied with Monte Carlo simulations, which compare the simulated compartment content distributions using different initial distributions for the parameters. The simulations indicate that the form of test distributions affect the distributions of compartment contents only for very simple models in the early stages. Later on, the distributions converge to a lognormal shape. The coefficients of variation of the initial distributions can be adjusted so that the resulting distributions resemble each other. Due to the lack of significant differences, lognormal distributions--which are found in most measurable body parameters--were used for further studies. The range of inter-subject variability can be estimated by comparing data generated with Monte Carlo simulations with observed data. For the plutonium model, data retrieved long times post intake are most suitable for this purpose when the redistribution of the radionuclide in the compartments is in a state of quasi-equilibrium and the ratio of plutonium in different compartments is nearly constant. For the estimation of inter-individual variability, the ratios of the main excretion paths and the organs of main burden can be used. The comparison of observed and simulated standard deviations indicates a value of 0.6 for the coefficient of variation for all transfer rates. The generated distributions show good agreement with the available data and thus confirm that the simulations can represent the inter-individual variation in the biokinetic plutonium model.

The CONRAD approach to biokinetic modeling of DTPA decorporation therapy.

Diethylene Triamine Pentaacetic Acid (DTPA) is used for decorporation of plutonium because it is known to be able to enhance its urinary excretion for several days after treatment by forming stable Pu-DTPA complexes. The decorporation prevents accumulation in organs and results in a dosimetric benefit, which is difficult to quantify from bioassay data using existing models. The development of a biokinetic model describing the mechanisms of actinide decorporation by administration of DTPA was initiated as a task in the European COordinated Network on RAdiation Dosimetry (CONRAD). The systemic biokinetic model from Leggett et al. and the biokinetic model for DTPA compounds of International Commission on Radiological Protection Publication 53 were the starting points. A new model for biokinetics of administered DTPA based on physiological interpretation of 14C-labeled DTPA studies from literature was proposed by the group. Plutonium and DTPA biokinetics were modeled separately. The systems were connected by means of a second order kinetics process describing the chelation process of plutonium atoms and DTPA molecules to Pu-DTPA complexes. It was assumed that chelation only occurs in the blood and in systemic compartment ST0 (representing rapid turnover soft tissues), and that Pu-DTPA complexes and administered forms of DTPA share the same biokinetic behavior. First applications of the CONRAD approach showed that the enhancement of plutonium urinary excretion after administration of DTPA was strongly influenced by the chelation rate constant. Setting it to a high value resulted in a good fit to the observed data. However, the model was not yet satisfactory since the effects of repeated DTPA administration in a short time period cannot be predicted in a realistic way. In order to introduce more physiological knowledge into the model several questions still have to be answered. Further detailed studies of human contamination cases and experimental data will be needed in order to address these issues. The work is now continued within the European Radiation Dosimetry Group, EURADOS.