Dosimetria Biològica per exposicions a altes dosis de radiació ionitzant i exposicions heterogènies

Student thesis: Doctoral thesis


Biological dosimetry allow us to estimate the dose to an exposure to ionizing radiation thought the analysis of a biomarker, and is an essential element in radiation protection. Among various biomarkers that can be used, dicentric chromosomes in metaphase from peripheral blood lymphocytes are considered the most useful, because their frequency is correlated in variations of the dose. This is true for doses up to 4-5 Gy, in higher doses the numbers of cells that achieve metaphase are very few and for this reason analysis becomes increasingly difficult. To overcome this limitation, the inhibition of the G2/M checkpoint by the addition of caffeine and the optimization of the culture duration, allows the mitigation of the mitotic delay, getting enough metaphases to perform the cytogenetic analysis. Through this methodology, a dose effect curve has been established for doses up to 25 Gy, it is based in a Gompertz model (that has never been used so far in biological dosimetry). The reliability of this model has been tested for whole and partial simulations. Furthermore, in most of radiological accidents where the irradiation is not homogeneous, up to now, its study was based in considering that one part of the body had been irradiated while the other part had not. This consideration becomes unrealistic because in the majority of accidents the exposed individuals received a gradient of doses. In order to study the heterogeneous exposures simulations, mixing irradiated blood at two different doses from a male and a female, allows the differentiation of the origin of each analyzed cell. Through the application of a mixture Poisson model the dicentric frequency from each fraction has been determined as well as the received dose and the initial proportion of cells irradiated at each dose. The possibility to estimate the received dose after high doses of exposure, as well as the better differentiation for the study of non homogeneous exposures is a very important contribution to the radioprotection field.
Date of Award10 Mar 2016
Original languageCatalan
SupervisorLeonardo Barrios Sanromà (Director), Rosa Caballin Fernandez (Director) & Joan Francesc Barquinero Estruch (Director)

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