The loss of unstable chromosome aberrations after the first postirradiation mitosis makes their use difficult in radiation dosimetry. We describe here a method which, in a cell population observed at this stage, allows retrospective estimation of the frequencies of the unstable aberrations induced at the time of irradiation, and their use as a dosimeter. The laws controlling the behavior of unstable aberrations during mitosis were defined from a large-scale experiment on irradiated human lymphocytes. For cells undergoing the first, second, or third mitosis after irradiation, relationships were determined between the frequency, at irradiation time, of acentric fragments not arising from formation of dicentrics or rings, and the ratio of dicentrics and centric rings appearing without acentric fragments to the total number of dicentrics plus rings. On the basis of this ratio, the method described here provides an assessment of the postirradiation mitotic activity in a cell population. This assessment permitted estimation of the cell distribution and frequency of dicentrics plus centric rings, and of the frequency of acentric fragments at the time of irradiation. The use of this method for retrospective dosimetry after whole-body irradiation under various conditions of exposure is illustrated.
Changes in the numbers of peripheral lymphocytes with chromosome aberrations were observed in cynomolgus monkeys after fractionated or acute 60Co irradiation at the same total doses. Immediately after irradiation, the yield of dicentrics decreased when the dose was fractionated but remained constant for 20 to 80 days, depending on the dose, when irradiation was acute. Lymphopenia was greater than expected when the dose was fractionated. The kinetics of the loss of chromosome aberrations and the changes in peripheral lymphocyte count occurring in monkeys after acute irradiation were compared to those observed in accidentally irradiated men.
La dosimétrie des expositions internes aux radionudéides incorporés repose sur une connaissance aussi complète que possible du comportement des substances radioactives dans l'organisme. Ceci est essentiel pour interpréter les mesnres d'activité faites dans le corps et ses émonctoires et les exprimer sous forme de quantités incorporées et de doses engagées. On décrit ici en termes généraux les voies d'incorporation, les transferts au sang, la distribution et la rétention dans les organes puis l'excrétion des radionucléides. L'ensemble de ces processus biocinétiques complexes est schématisé de façon a pouvoir être représenté par des modèles mathématiques accessibles au calcul. Depuis une dizaine d'années, la Commission internationale de protection radiologique a entrepris la révision systématique de toutes ses recommandations pour tenir compte de l'évolution des connaissances : révision des facteurs de pondération du risque stochastique, révision complète du modèle respiratoire, révision de nombreux facteurs d'absorption digestive, élaboration de modèles spécifiques de certains organes et de certains éléments. Cette démarche a conduit a réactualiser la plupari des coefficients de dose pour les travailleurs.ABSTRACT Dosimetric models for intakes of radionuclides by workers.Internat dosimetry from intakes of radionuclides is based, as accurately as possible, on the understanding of radioactive material behaviour in the body. This is most important to the interpretation of bioassay measurements for intake evaluation and commiîîed dose assessment. General description is made of intake routes, blood uptake, distribution to organs, retention and excretion of radionuclides. Those complex biokinetic processes are modelled such as to allow mathematical dculations. Since about ten years, the International commission on radiological protection has been incorporating recent knowledge in this field and revising superseded recommendations: this is the case for stochastic risk weighting factors, respiratory tract models, digestive absorption factors, models for specific organs and specific nudides. This work has proàuced a set of new dose coefficients for workers to replace most of the former ones.
*Le nombre de pages élevé d e cet article est atypique du point de vue des critères d'acceptation d e Radioprotection : ceci est dû au fait que cet article était initialement prévu dans un numéro spécial consacré à la dosimétrie.
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