1,721,410 research outputs found
Biokinetic Modelling of DTPA Decorporation Therapy: the CONRAD Approach
No full textAdministration of diethylene triamine pentaacetic acid (DTPA) can enhance the urinary excretion rate of plutonium (Pu) for several days, but most of this Pu decorporation occurs on the first day after treatment. The development of a biokinetic model describing the mechanisms of decorporation of actinides by administration of DTPA was initiated as a task of the coordinated network for radiation dosimetry project. The modelling process was started by using the systemic biokinetic model for Pu from Leggett et al. and the biokinetic model for DTPA compounds of International Commission on Radiation Protection Publication 53. The chelation of Pu and DTPA to Pu-DTPA was treated explicitly and is assumed to follow a second-order process. It was assumed that the chelation takes place in the blood and in the rapid turnover soft tissues compartments of the Pu model, and that Pu-DTPA behaves in the same way as administered DTPA. First applications of this draft model showed that the height of the peak of urinary excretion after administration of DTPA was determined by the chelation rate. However, repetitions of DTPA administration shortly after the first one showed no effect in the application of the draft model in contrast to data from real cases. The present draft model is thus not yet realistic. Therefore several questions still have to be answered, notably about where the Pu-DTPA complexes are formed, which biological ligands of Pu are dissociated, if Pu-DTPA is stable and if the biokinetics of Pu-DTPA excretion is similar to that of DTPA. Further detailed studies of human contamination cases and experimental data about Pu-DTPA kinetics will be needed in order to address these issues. The work will now be continued within a working group of EURADOS
Americium in the beagle dog: Biokinetic and dosimetric model
No full textA biokinetic model of the systemic distribution of americium in the beagle dog is presented. The model is based on a previous biokinetic model of plutonium. The data sets used for the development of the model were the measurements of excreted activity (urine and feces) and organ burdens (skeleton, liver, and other soft tissues) for different levels of initial injected activity. In developing the model, the compartmental structure of the skeleton of the plutonium model was adopted, and only the numerical values of parameters were adapted. The model well describes the fractions of americium in the skeleton, liver, and soft tissues and the total fraction excreted in urine and feces. The tuning of the liver clearance parameter provides a realistic description of the change in the partitioning between liver and skeleton for different injection levels. The most significant features of the biokinetics and dosimetry of americium and plutonium in beagles are compared. The total fractions of the clearance to the skeleton and the liver are roughly equal to the value for plutonium, but the partitioning of americium between these organs is reversed with respect to the partitioning of plutonium. Am doses to liver and skeleton are similar to Pu doses, owing to some counteracting factors. For the highest injection level, the liver mass is dependent on the time post injection. For the skeletal tissues, the dose to the cortical endosteum by far exceeds the dose to the trabecular endosteum and the red marrow. The model provides the basis for statistical survival analyses and risk estimates
Standardized methods for measuring radionuclides in drinking water
No full textIn 2002 the Italian Standardisation Organisation (UNI) - Nuclear Energy Commission (UNICEN) - appointed a working group with the main task of writing a set of standards on drinking water measurements. To date two standards have been designed, namely, for total alpha- and beta-activity, and 222Rn. Further procedures are under development for measuring 226Ra and U isotopes, and gamma-emitting radionuclides in water. The paper gives an overview of these standards, both developed and under study, with special attention to the validation of the methods
Plutonium Biokinetics in Human Body
No full textThe biokinetic model presented by the International Commission on Radiological Protection (ICRP) in the Publication 67 represents one of the basic tools far evaluating the risk of exposure to an internal contamination from Plutonium. However it is characterized by some assumptions that have no clear physiological explanation, but that were introduced to have a closer fit to the available data from studies on humans, particularly in relation to the urinary excretion at long time. Such assumptions are not only a correction of model's prediction of Plutonium urinary excretion, but it was showed that they are the leading process in determining the urinary excretion after already 100 days post intake. Yet, even with such corrections, this biokinetic model shows still difficulties in describing the metabolism of Plutonium in human body.In recent years, as data relating to the urinary excretion of Plutonium at long time become more and more available, an enhancement of the urinary excretion long after intake was observed. The application of such mode l on these actual cases would result in a significant overestimation of the dose, with important consequences not only from a scientific, but even from a legal point of view.Owing to these considerations the biokinetic model from ICRP was further developed. Particular attention was paid to the predictions of the urinary excretion, because this is the most common and feasible technique far monitoring the exposure to the risk of an internal contamination of Plutonium. The ICRP model was modified on the basis of the available data from studies of Plutonium metabolism in humans in order to get accurate predictions of the urinary excretion without the ICRP assumptions that can not be physiologically supported. The optimized model obtained from this analysis predicts also values for the fecal excretion and blood retention of Plutonium that agrees better to the available data than ICRP model does.Dose coefficients and analytical expressions that approximates the urinary excretion of Plutonium predicted by the optimized mode I were calculated in order to allow an easy implementation of the model in the monitoring routine of radiation protection.Furthermore a sensitivity analysis was carried out on the transfer rates of the model in order to point out the most significant parameters in determining the urinary excretion of Plutonium and, at a lesser extent, the fecal excretion and the blood retention.On the basis of the results of the sensitivity analysis an uncertainty analysis was also carried out to evaluate the range of variation of the model transfer rates that would reproduce the variability of the urinary excretion observed in humans. It is therefore possible to have an indication about the possible values of the transfer rates that can be assumed far a specific subject of the population.The optimized model was finally used to describe the urinary excretion of an actual case of contamination. This subject is today one of the most known and studied worldwide because a great number of data are available since his contamination in 1983. Furthermore he represents one the most significant examples of enhancement of the urinary excretion of Plutonium at long time after exposure
Interruzioni volontarie di gravidanza (IVG) per malformazioni congenite rilevate nel territorio della ex USL 13 - Area Livornese (1992-1994).
No full textIDEAS Work Package 3 Evaluation of Incorporation Cases
No full textIl progetto IDEAS per lo sviluppo di 'Linee guida generali per la stima della dose impegnata dai dati di monitoraggio della incorporazione' (contratto ED FIKR-CT2001-00160) è articolato in 5 moduli (Work Package WP). Al momento 3 di essi sono giunti a conclusione.Nel Work Package 1 (WPI) è stato realizzato un InternaI Contamination Database raccogliendo le descrizioni di scenari di contaminazione con le relative misure di follow-up recuperati dalla letteratura, da altri rapporti e giudicati sufficientemente interessanti per la valutazione di dose interna.Nel WP2 il codici di calcolo IMIE (sviluppato dal Radiation Protection Institute ucraino) è stato migliorato ed adattato alle esigenze del progetto IDEAS.Nel WP3 molti casi di studio sono stati valutati dai diversi contraenti usando due software di riferimento; le valutazioni sono state raccolte ed è stato realizzato un database denominato Evaluation of Cases. Esso contiene il riassunto delle informazioni relative a 95 valutazioni su 52 casi (17 radioisotopi) permettendo la comparazione di differenti approcci alla valutazione di dose, per lo stesso scenario di contaminazione e fornendo il collegamento all'InternaI Contamination Database, dove possono essere reperiti i dati originari di monitoraggio. Dal Evaluation of Cases Database è anche possibile aprire i documenti che descrivono nel dettaglio ogni valutazione che presentano l'approccio del contraente, le ipotesi assunte ed i parametri usati.La selezione dei casi che dovevano essere valutati era stata effettuata sulla base dei radioisotopi coinvolti o della miscela presente nello scenario, della complessità presente nell'insieme dei dati (tipologie dei dati di monitoraggio) o di argomenti speciali che devono essere considerati nelle linee guida.Nel presente rapporto sono descritti i risultati del Work Package 3.The IDEAS project for the development of GeneraI guidelines far the estimation of committed dose tram incorporation monitoring data (ED contract FIKR-CT2001-00160) is divided in 5 Work Packages (WP). At the moment 3 of them have been concluded.In the WP1 the Internal Contamination Database has been set up, collating descriptions of case scenarios and the follow up measurements of incidental cases found in the open literature or in other reports, judged to be interesting far internal dose assessment.In WP2 the IMIE code (developed by Radiation Protection Institute of Ukraine) has been improved and fitted to the special requirements of the IDEAS project.In WP3 many case studies have been evaluated by contractors using reference software, the evaluations were collated and an Evaluation of Cases Database has been set up. It contains a summary of information for 95 evaluations on 52 cases (17 radioisotopes) permitting the comparison of different approaches to evaluation on the same case scenario, and providing links to the IDEAS Internal Contamination Database, were the original monitoring data can be found. From the database it is also possible to open the file describing each evaluation where detailed information on each contractor' s approach, assumed hypotheses and parameters can be found.The selection of cases to be evaluated was made on the basis of the radioisotope or mixture present in the case scenario, complexity present in the data set (e.g. multiple types of monitoring data) and special issues to be considered in the guidelines
Modelli di varianza delle misure di bioassay e stima dell'intake in dosimetria interna
No full textNel caso di monitoraggio individuale della contaminazione interna a seguito di un evento anomalo o di incidente vengono solitamente effettuate misure di follow up per l'affinamento della valutazione dell'intake e la successiva valutazione della dose efficace impegnata.Come emerso nel corso di un esercizio di interconfronto sulla valutazione della dose condotto recentemente nel contesto italiano (VALDOSE), l'approccio più comune è basato sul metodo del calcolo dell'intake medio, ossia dell'intake finale come media di ogni singola stima di intake ottenuta sulla base dell'i-esima misura e del relativo i-esimo valore di ritenzione/escrezione del modello.Adottando un approccio più generale dal punto di vista matematico il presente lavoro mostrerà come, partendo da una funzione generale che esprima il grado di accordo fra misure sperimentali e modello, sia possibile ottenere diverse espressioni della stima dell'intake (come il sopraccitato 'intake medio') partendo da diversi modelli di varianza delle misure di monitoraggio.Questa formalizzazione matematica permetterà di comprendere il significato delle varie metodologie adottate per il calcolo dell'intake evidenziando le assunzioni che implicitamente vengono effettuate nell'adozione di un modello di calcolo dell'intake e che spesso non sono debitamente considerate dal valutatore di dose.I modelli di calcolo dell'intake saranno oggetto di discussione all'interno delle attività del progetto europeo IDEAS 'General guidelines for the estimation of committed doses from incorporation monitoring data' che sta affrontando queste problematiche per proporre un approccio unico nel contesto europeo
Internal Dose Assessments: Uncertainty Studies and Update of Ideas Guidelines and Databases within CONRAD Project
No full textThe work of Task Group 5.1 (uncertainty studies and revision of IDEAS guidelines) and Task Group 5.5 (update of IDEAS databases) of the CONRAD project is described. Scattering factor (SF) values (i.e. measurement uncertainties) have been calculated for different radionuclides and types of monitoring data using real data contained in the IDEAS Internal Contamination Database. Based upon this work and other published values, default SF values are suggested. Uncertainty studies have been carried out using both a Bayesian approach as well as a frequentist (classical) approach. The IDEAS guidelines have been revised in areas relating to the evaluation of an effective AMAD, guidance is given on evaluating wound cases with the NCRP wound model and suggestions made on the number and type of measurements required for dose assessment
Italian intercomparison exercise on internal dose assessment
No full textIn 2001, the Radiation Protection Institute of ENEA promoted an Italian intercomparison exercise on internal dose assessment addressed to the qualified experts in radiation protection, following the coming into force in Italian law of the EURATOM 96/29 Directive. Five case studies of occupational exposure related to the Italian situation are used. The considered radioisotopes are : 60Co, 89Sr, 125I, 131I, and 222Rn + NORM (238U-235U-232Th). Data related to WBC, thyroid and urine excretion measurements, as well as radionuclide air concentration in the workplace, are provided to the participants. The results related to medical, industrial and Rn occupational exposure are well represented as means of log-normal distributions with values of the geometric standard deviation less than 2. A wider spread of results is present for the evaluation of occupational exposure to NORM
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