Sudbrock F.,University of Cologne |
Uhrhan K.,University of Cologne |
Rimpler A.,Institute Atmospharische Radioaktivitat |
Schicha H.,University of Cologne
Radiation Measurements | Year: 2011
Radiation exposure for the staff in nuclear medicine departments is inevitable. After application of radiopharmaceuticals the patient himself becomes a radioactive source. Consequently, we need detailed information on the extent of radiation exposure for each single person dealing with radioactive sources and patients in nuclear medicine. In this work, dose rates of a variety of radioactive sources - radiopharmaceuticals and patients - in nuclear medicine were investigated. For this purpose different detectors (dosimeters, survey-meters) were used and different sources were measured for several distances between source and detector. The "radioactive patient" as a source can be considered as uncritical. However, this assumption only holds if members of the personnel keep a sufficient distance to the patient of at least 1 m. If treatments in the vicinity of the patient become necessary, the time spent in a closer distance should be limited. The handling of radiopharmaceuticals often involves close contact to the radioactive source. For the β-radiation or in the mixed β,γ-radiation field of several high energy beta emitters ( 32P, 68Ga, 90Y, 188Re) the ambient dose equivalent rate at 10 mm depth together with the directional dose equivalent rate at 0° and 0.07 mm depth have to be determined. Especially for the beta emitters mentioned above these dose rates are very high. For instance the specific dose rate for 90Y yields 4.6 Sv/(GBqh) when dose rate measurements were performed in the closest distance to a glass vial that was practicable. Survey-meters that are only capable of measuring photons fail to provide even a rough approximation of the actual dose rate. Preparations of radiopharmaceuticals with these nuclides may consequently cause a high extremity exposure of laboratory staff. This requires measurements, demands training and a strict compliance with the established radiation safety standards. © 2011 Elsevier Ltd. All rights reserved.
Heidenreich W.F.,German Research Center for Environmental Health GmbH |
Heidenreich W.F.,Helmholtz Center for Environmental Research |
Tomasek L.,National Radiation Protection Institute, Czech Republic |
Grosche B.,Institute Atmospharische Radioaktivitat |
And 2 more authors.
Radiation and Environmental Biophysics | Year: 2012
The biologically based two-stage clonal expansion (TSCE) model is used to analyze lung cancer mortality of European miners from the Czech Republic, France, and Germany. All three cohorts indicate a highly significant action of exposure to radon and its progeny on promotion. The action on initiation is not significant in the French cohort. An action on transformation was tested but not found significant. In a pooled analysis, the results based on the French and German datasets do not differ significantly in any of the used parameters. For the Czech dataset, only lag time and two parameters that determine the clonal expansion without exposure and with low exposure rates (promotion) are consistent with the other studies. For low exposure rates, the resulting relative risks are quite similar. Exposure estimates for each calendar year are used. A model for random errors in each of these yearly exposures is presented. Depending on the used technique of exposure estimate, Berkson and classical errors are used. The consequences for the model parameters are calculated and found to be mostly of minor importance, except that the large difference in the exposure-induced initiation between the studies is decreased substantially. © Springer-Verlag 2012.
Meisenberg O.,Helmholtz Center for Environmental Research |
Meisenberg O.,Institute Atmospharische Radioaktivitat |
Tschiersch J.,Helmholtz Center for Environmental Research
Radiation Measurements | Year: 2015
Determining the activity size distribution of radioactive aerosol particles requires sophisticated and heavy equipment, which makes measurements at large number of sites difficult and expensive. Therefore three methods for a retrospective determination of size distributions from aerosol filter samples in the laboratory were tested for their applicability. Extraction into a carrier liquid with subsequent nebulisation showed size distributions with a slight but correctable bias towards larger diameters compared with the original size distribution. Yields in the order of magnitude of 1% could be achieved. Sonication-assisted extraction into a carrier liquid caused a coagulation mode to appear in the size distribution. Sonication-assisted extraction into the air did not show acceptable results due to small yields. The method of extraction into a carrier liquid without sonication was applied to aerosol samples from Chernobyl in order to calculate inhalation dose coefficients for 137Cs based on the individual size distribution. The effective dose coefficient is about half of that calculated with a default reference size distribution. © 2015 Elsevier Ltd. All rights reserved.
Berg H.-P.,Institute Atmospharische Radioaktivitat |
Rowekamp M.,GRS Society for plants and Reactor Safety
International Topical Meeting on Probabilistic Safety Assessment and Analysis 2013, PSA 2013 | Year: 2013
The German nuclear regulation has been significantly enhanced recently promulgating stateof-the-art "Safety Requirements to Nuclear Power Plants" published in January 2013. These enhancements also concern safety demonstrations by deterministic as well as probabilistic safety assessment. The update of the regulatory framework does also concern the technical documents on PSA (Probabilistic Safety Analysis) methods and data supplementing the German Guide for probabilistic safety assessment. While PSA was mainly used in Germany in the frame of periodic safety reviews (PSR) in the past, PSA applications as a supplementary analytical tool to be used in the nuclear regulatory framework shall be further extended in the future. In the frame of the Safety Requirements relative probabilistic criteria are being applied for plant or organizational modifications. An expert group has already started an activity to extend the applications of PSA to regulatory issues beyond PSR, such as regulatory oversight on modifications applied by the licensee or evaluation of events or phenomena which have a significant effect on PSA results. The most recent activities with regard to PSA as supplementary tool for safety assessment focus on improvements with respect to low power and shutdown PSA, considering fuel damage states, and in addition covering internal hazards PSA (in particular fire in the scope, providing updates of data for fire protection features. Moreover, clarifications regarding level 2 PSA are provided resulting from the practical application. Further activities aim on applying enhanced methods and providing additional data for human factor analysis using the THERP method. Moreover, a more complete and systematic consideration of external hazards is intended, in particular for seismic events and external flooding. Last not least methods and data for Fire PRA have been improved significantly in the recent past. This shall be clearly reflected in the guidance documents on PSA methods and data as well. The material for the update of methods and data for PSA application in the frame of PSR should be provided until the end of the year in order to issue a supplement to the existing document in 2014.
Brix G.,Federal office for Radiation Protection |
Brix G.,Institute Atmospharische Radioaktivitat |
Griebel J.,Federal office for Radiation Protection |
Kiessling F.,RWTH Aachen |
Wenz F.,University of Mannheim
European Journal of Nuclear Medicine and Molecular Imaging | Year: 2010
Purpose: Technical developments in both magnetic resonance imaging (MRI) and computed tomography (CT) have helped to reduce scan times and expedited the development of dynamic contrast-enhanced (DCE) imaging techniques. Since the temporal change of the image signal following the administration of a diffusible, extracellular contrast agent (CA) is related to the local blood supply and the extravasation of the CA into the interstitial space, DCE imaging can be used to assess tissue microvasculature and microcirculation. It is the aim of this review to summarize the biophysical and tracer kinetic principles underlying this emerging imaging technique offering great potential for non-invasive characterization of tumour angiogenesis. Methods: In the first part, the relevant contrast mechanisms are presented that form the basis to relate signal variations measured by serial CT and MRI to local tissue concentrations of the administered CA. In the second part, the concepts most widely used for tracer kinetic modelling of concentration-time courses derived from measured DCE image data sets are described in a consistent and unified manner to highlight their particular structure and assumptions as well as the relationships among them. Finally, the concepts presented are exemplified by the analysis of representative DCE data as well as discussed with respect to present and future applications in cancer diagnosis and therapy. Results: Depending on the specific protocol used for the acquisition of DCE image data and the particular model applied for tracer kinetic analysis of the derived concentration-time courses, different aspects of tumour angiogenesis can be quantified in terms of well-defined physiological tissue parameters. Conclusions: DCE imaging offers promising prospects for improved tumour diagnosis, individualization of cancer treatment as well as the evaluation of novel therapeutic concepts in preclinical and early-stage clinical trials. © 2010 Springer-Verlag.