Parametric analysis of a biokinetic model: a contribution to the study of model reliability

I M. C. Lourenc, II J. L. Lipsztein and III C. L. Szwarcwald/ 1 Instituto de Radioproteção e Dosimetria Av. Salvador Allende, s/n, CEP 22780–160, Rio de Janeiro – RJ, Brazil / 2 Instituto de Biologia, Universidade do Estado do Rio de Janeiro Av. 28 de Setembro, 87, CEP 20551–030, Rio de Janeiro – RJ, Brazil/ 3 Departamento de Saúde, Fundação Oswaldo Cruz Av. Brasil, 4365, CEP 21045–900, Rio de Janeiro – RJ, BrazilMade available in DSpace on 2010-08-23T16:58:36Z (GMT). No. of bitstreams: 3 license.txt: 1848 bytes, checksum: c1e4622844147e1ffa7fb904370b866a (MD5) LANDMANN_Parametric Analysis Biokinetic_1998.pdf: 34180 bytes, checksum: 8316bfeb8d5f44135fb59e8aa558ce3f (MD5) LANDMANN_Parametric Analysis Biokinetic_1998.pdf.txt: 19050 bytes, checksum: c9f06ee7b2adb8333ee76518dc7b35e1 (MD5) Previous issue date: 1998Made available in DSpace on 2010-11-04T14:20:03Z (GMT). No. of bitstreams: 3 LANDMANN_Parametric Analysis Biokinetic_1998.pdf.txt: 19050 bytes, checksum: c9f06ee7b2adb8333ee76518dc7b35e1 (MD5) LANDMANN_Parametric Analysis Biokinetic_1998.pdf: 34180 bytes, checksum: 8316bfeb8d5f44135fb59e8aa558ce3f (MD5) license.txt: 1848 bytes, checksum: c1e4622844147e1ffa7fb904370b866a (MD5) Previous issue date: 1998Instituto de Radioproteção e Dosimetria. Rio de Janeiro, RJ, Brasil.Universidade do Estado do Rio de Janeiro. Instituto de Biologia. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto de Comunicação e Informação Científica e Tecnologia em Saúde. Rio de Janeiro, RJ, Brasil.Models for simulating radionuclide distribution in the human body involve assumptions on the biokinetic behaviour of the material. An important problem in biokinetic modelling is the correct assignment of transfer coefficients and biological half-lives to tissue compartments. The purpose of this study is the analysis of the variations of the radionuclide contents in the tissue compartments related to variations in the transfer coefficients from blood to the compartments and to variations in the compartments' biological half-lives. A generalised systemic recycling model, consisting of four tissue compartments and two excretion pathways, was used for the parametric analysis. A continuous intake directly to the blood was chosen for this study. Activities in the compartments were calculated for different times, following random selection of the transfer coefficients and half-lives. A computer code was developed to perform the random selection of parameters. Three different case studies were analysed, where different intervals of variation of half-lives in the four compartments were chosen: (a) the same range of variation was assigned to all compartments, (b) the intervals were chosen so that one compartment had a significantly longer half-life than the others, and (c) one compartment had a significantly shorter half-life than the others. Two cases for the intervals of variation of the transfer coefficients were investigated: (a) the same range for the variation of all transfer coefficients from blood to compartments was assumed, and (b) the interval of the variation of one transfer coefficient was significantly larger than the others. A multiple regression analysis method was applied to analyse the results. In this paper the detailed results of the parametric analysis are presented

Metabolism of Ingested Uranium and Radium

Metabolic models for U and Ra are described to estimate the risks to human health from ingesting these elements in drinking water. Chemical toxicity, which is relevant to U in its natural, depleted or slightly enriched state, is addressed, as are the radiotoxicity and the radiobiological effects of the important alpha-emitting isotopes of Ra, including /sup 224/Ra, /sup 226/Ra, and /sup 228/Ra. This paper estimates the kinetics of skeletal U deposition, so that risk coefficients for bone cancer induction can be applied. Skeletal cancer is regarded as the major potential radiobiological effect of ingested alpha-emitting radioisotopes of Ra and the presumed radiobiological effect of U, if any. Best estimates of normal U metabolism are used, because even in extreme cases the amounts of U or Ra ingested in potable water are not great enough to chemically or radiobiologically modify their metabolic behavior