Biomedical subjects

H Doerfel

Publications and source records attributed to H Doerfel.

8 recordsLinked to original sources

PubMed2006

General guidelines for the assessment of internal dose from monitoring data: progress of the IDEAS project.

In recent major international intercomparison exercises on intake and internal dose assessments from monitoring data, the results calculated by different participants varied significantly. Based on this experience the need for harmonisation of the procedures has been formulated within an EU 5th Framework Programme research project. The aim of the project, IDEAS, is to develop general guidelines for standardising assessments of intakes and internal doses. The IDEAS project started in October 2001 and ended in June 2005. The project is closely related to some goals of the work of Committee 2 of the ICRP and since 2003 there has been close cooperation between the two groups. To ensure that the guidelines are applicable to a wide range of practical situations, the first step was to compile a database of well-documented cases of internal contamination. In parallel, an improved version of an existing software package was developed and distributed to the partners for further use. A large number of cases from the database was evaluated independently by the partners and the results reviewed. Based on these evaluations, guidelines were drafted and discussed with dosimetry professionals from around the world by means of a virtual workshop on the Internet early in 2004. The guidelines have been revised and refined on the basis of the experiences and discussions in this virtual workshop. The general philosophy of the Guidelines is presented here, focusing on the principles of harmonisation, optimisation and proportionality. Finally, the proposed Levels of Task to structure the approach of internal dose evaluation are reported.

Algorithms↗

PubMed2006

IDEAS internal contamination database: a compilation of published internal contamination cases. A tool for the internal dosimetry community.

In the scope of the IDEAS project to develop General Guidelines for the Assessment of Internal Dose from Monitoring data, two databases were compiled. The IDEAS Bibliography database contains references dealing with problems related to cases of internal contamination. The IDEAS Internal Contamination Database now contains more than 200 cases of internal contamination. In the near future, the IDEAS Internal Contamination database will be made available to the internal dosimetry community. The database has several potential applications, including: training, testing biokinetic models, testing software for calculating intakes and doses from bioassay data, comparison of data from a new accidental intake with that from previous exposures to similar materials. The database is by no means complete, and this presentation is also an appeal for internal contamination cases to extend and update it.

Biological Assay↗

PubMed2003

Uncertainty analysis of the urinary excretion of plutonium.

A quantitative estimate of the uncertainty of the urinary excretion of plutonium predicted by available biokinetic models is provided. Urinary excretion is primarily considered here because the monitoring of internal contamination of plutonium mainly relies on measurements of activity in urine samples. A previous paper has identified the most significant transfer rates for urinary plutonium excretion following an acute intake. That analysis is used here as a screening method to reduce the number of model parameters to be considered. A log-normal distribution was assumed for the probability distribution of the model parameters. The spread of the values, represented by the geometric standard deviation (GSD), is explicitly calculated, as few indications of the range of variation of systemic transfer rates are available. Different values for the GSD were considered. Assuming a certain GSD for all the systemic rate constants, random values of the rates were generated (by means of a Monte Carlo simulation with a Latin hypercube sampling scheme) and the resulting predictions of urine bioassay measurements were calculated. The comparison of the mean and variance of the predictions with the available data from several studies performed on different subjects provides information about the GSD of model parameters that represents the intersubject variation of transfer parameters.

Animals↗

PubMed2003

Lessons learned from interlaboratory comparisons of bioassay data interpretation.

When a set of bioassay data is given to two different dosimetrists, it is likely that these data will be interpreted differently, that different methods and dosimetric models will be applied and therefore different numerical values will be obtained. Thus, it is important for laboratories dealing with internal dosimetry to undergo performance testing procedures such as interlaboratory comparisons of bioassay data interpretation. Several intercomparison exercises have already been organised at national and international levels. The largest one so far was the 3rd European Intercomparison Exercise on Internal Dose Assessment, which has been organised in the framework of the EULEP/EURADOS Action Group, 'Derivation of parameter values for application to the new model of the human respiratory tract for occupational exposure'. The most important lesson learned from these intercomparison exercises was the need to develop agreed guidelines for internal dose evaluation procedures to promote harmonisation of assessments between organisations and countries.

Benchmarking↗

PubMed2003

Guidance on internal dose assessments from monitoring data (project IDEAS).

Several international inter-comparison exercises on intake and internal dose assessments from monitoring data led to the conclusion that the results calculated by different participants varied significantly, mainly due to the broad variety of methods and assumptions applied in the assessment procedure. Based on these experiences, the need of harmonisation of the procedures has been formulated as an EU research project under the 5th Framework Programme, with the aim of developing general guidelines for standardising assessments of intakes and internal doses. In the IDEAS project, eight institutions from seven European countries are participating, also using inputs from internal dosimetry professionals from across Europe to ensure broad consensus in the outcome of the project. To ensure that the guidelines are applicable to a wide range of practical situations, the first step will be to compile a database on well documented cases of internal contamination. In parallel, an improved version of existing software will be developed and distributed to the partners for further use. Many cases from the database will be evaluated independently by more partners using the same software and the results will be discussed and the draft guidelines prepared. The guidelines will then be revised and refined on the basis of the experiences and discussions of two workshops, and an intercomparison exercise organised in the frame of the project which will be open to all internal dosimetry professionals.

Body Burden↗

PubMed2001

Sensitivity analysis of the urinary excretion of plutonium.

The transfer parameters of a new age-related model for plutonium metabolism, which have the largest influence on urinary excretion, are determined by applying a sensitivity analysis and assuming a direct uptake into blood. Realistic cases of contamination via ingestion and inhalation were considered as well and sensitivity coefficients for non-systemic parameters were calculated. The most important parameters in relation to the path of intake are identified and the effects of the modifying factors proposed by the ICRP in the case of alteration of respiratory tract physiology are briefly examined.

Absorption↗

PubMed1985

The metabolism of radiohafnium in marmosets and hamsters.

The whole body retention of 181Hf was studied in marmosets (Callithrex jacchus) and found to be closely similar to that in rats and Chinese hamsters. Limited tissue distribution studies suggest a higher uptake in liver and much lower deposition in skin and muscle in the marmoset as compared to the rat or Chinese hamster. Studies in Chinese hamsters showed that treatment with the chelating agent diethylenetriaminepentaacetic acid resulted in only a small reduction in the whole body retention of 181Hf. The absorption of orally administered 181Hf, in various chemical forms, was found to be between 0.04 and 0.13% of the ingested dose and was unaffected by age between 5 and 21 months but was increased by fasting. The measured absorption of 181Hf in Chinese hamsters and in rats was similar to that of plutonium suggesting that radiohafnium could be used as a surrogate for plutonium for selected studies in human volunteers.

Animals↗

PubMed1985

Inhalation of U aerosols from UO2 fuel element fabrication.

Publication No. 30 of the International Commission on Radiological Protection (ICRP) assigns the uranium oxides UO2 and U3O8 to transportability class Y, i.e. the half-life of these compounds in the lungs is about 500 days. This assignment seemed not to be in accordance with our experience resulting from incorporation surveillance during UO2 fuel element fabrication. Persons who worked in atmospheres containing UO2 aerosols with activity concentrations significantly above the derived air concentrations (DAC) for class Y U showed much lower activity in the lungs than would be expected according to the ICRP. To understand this discrepancy, aerosol concentrations and aerosol particle-size distributions at work places with the possibility of UO2 incorporation, the activity of urine and feces and the lung activity of persons working at these places were measured in an investigation program. The results are only consistent with the ICRP lung model if one uses a measured biological half-life in the lungs of 109 days and a measured AMAD of 8.2 micron instead of the ICRP standard assumptions of 500 days and 1.0 micron, respectively. ICRP Publication No. 30 recommends application of specific parameters for health physics instead of standard model values. For the special conditions in our UO2 fuel fabrication plant we therefore derive limits of air concentrations, lung activities and fecal and urinary activity concentrations by applying our measured particle-size and lung-retention parameters to the ICRP model. Our special derived limits in comparison to class Y limits for U after ICRP Publication No. 30 for a 1-micron AMAD and 500-day half-life (in brackets) are: (a) annual limit of intake: 6 X 10(4) Bq/y (1 X 10(3) Bq/y); (b) derived air concentration: 20 Bq/m3 (0.6 Bq/m3); (c) derived lung activity: 1.6 X 10(3) Bq; (d) derived fecal activity: 14 Bq/day; and (e) derived urine activity: 8.9 Bq/day. The committed dose equivalents calculated from our measured data and from our modified derived limits proved consistent for the different incorporation control methods (determination of air concentration, lung, fecal or urinary activity). The authors recommend that in accordance with ICRP Publication No. 30, the national rules and regulations on activity incorporation provide the possibility to derive special limits from specific work-place parameters such as particle-size distributions and biological half-lives, thus supplementing the ICRP standard assumptions of 1 micron AMAD and biological half-lives of 0.5 days for class D, 50 days for class W and 500 days for class Y compounds.

Adult↗