O.4 - A comparative study of the cytogenetic responses for homo- and heterogeneous exposures of human T-lymphocytes

Abstract

Introduction: Biological dosimetry is central in the assessment and mitigation of large scale radiation accidents and occupational over-exposures. Several biological endpoints have been successfully employed to estimate doses for both in vitro and in vivo exposures. Comprehensive statistical analysis of the dose–response parameters can yield more information than mere quantitative dose estimates. Qualitative aspects of the radiation type and dose distribution can be predicted, which is important for real world biodosimetry applications. Materials and Methods: Equivalent total body dose estimates were prepared for blood samples exposed to 60Co gamma-rays at doses ranging from 1 to 6Gy. The samples were subsequently dilutedwith sham irradiated blood to yield a range of total body dose equivalents between 0 and 4 Gy. Dicentric formation frequency in lymphocyte metaphase spreads was quantified using a semi-automated image analysis system. Results: Cytogenetic aberration frequencies for each irradiation and dilution condition were translated to whole body dose values using dose– response curves established in the laboratory. The measured values were in agreement with the calculated estimates (P-value > 0.05). The overdistribution of chromosomal aberrations correlated with the non-uniformity of the radiation applied; which is reflected by the indices of dispersion (σ2/ μ > 1.2) for heterogeneously exposed samples. Conclusion: The degree of non-uniformity of exposures can be predicted on the basis of over-dispersion parameters calculated using advanced statistical analysis of dicentric frequency distributions.