Research Information System
Turkish J. Of Medical Science., vol.30, pp.563-569, 2000 (Peer-Reviewed Journal)
Abstract: Control radiation dose-response curves are necessary in evaluating the absorbed radiation dose of similar radiation quality following radiation accidents or in monitoring the health of both the public and radiation workers. Each biological dosimetry laboratory should establish its own control dose-response data. In this study our aim was to establish control curves for 200 kVp X-rays in our laboratory in order to estimate absorbed radiation doses following exposures. Blood samples from healthy individuals with no radiation working history were irradiated in heparinized tubes at 10 different doses 0.10-5.00 Gy. Cells from irradiated whole blood were incubated in culture containing phytohemagglutinin for lymphocyte propagation. Dividing cells were blocked at metaphase, fixed, stained, and unstable chromosome aberrations were scored. Yields of dicentrics and excess acentrics following different radiation doses were used to establish control curves. The data were fitted to the linear-quadratic (LQ) equation. The parameters of the LQ equations were used in the Qdr method to estimate an absorbed radiation dose in five people working with medical X-ray radiation for a relatively long time. Estimations showed that four workers received doses below the permissible levels but one showed an indication of overexposure. Key Words: Biological dosimetry, X-ray, chromosome aberrations. Introduction Biological dosimetry, following an investigation of using chromosome aberrations from metaphase blocked cells (1,2), has gained an acceleration for evaluating the absorbed radiation dose in circulating lymphocytes of radiation victims or radiation workers (3-6). The maximum permissible whole-body dose to radiation worker is 50 mSv per year, or 30 mSv per quarter, or to a member of the public is about 10 times less than these values (7). Any violations of these limits give an alert for the safety of both radiation workers and normal individuals. Therefore there is a need to define any overexposed individuals in order to apply any immediate medical care. Radiation dose estimations from blood lymphocytes provide a valuable tool especially in acute and homogenous irradiations. Distribution of unstable chromosome aberrations, particularly dicentrics, among cells follow the Poisson statistics. However, estimations based on past exposures and non-uniform irradiations are difficult due to lymphocyte life-time and dilution of damaged cells from undamaged parts of the body respectively (7). The Q dr method of Sasaki (3) relating aberrations (dicentrics and centric rings) only in damaged cells to a radiation dose overcomes the problems of dependency on time after exposure and inhomogenous irradiation. Differences exist in the background frequencies of chromosome aberrations in different populations. These differences are due to biological diversity, geographical situation, atmospheric pollution, the extent of environmental clastogenic chemicals, or the use of medical drugs alone or in combinations (8,9). Due to the variations of the background frequencies of aberrations, each biological dosimetry laboratory should establish its own control dose-response curves for any different LET radiations available (2). Therefore, we intend to establish in this paper a control curve for 200 kVp X-rays and to apply this curve to estimate if there is any absorbed radiation dose over the permissible levels in five radiation workers. Turk J Med Sci 30 (2000) 563-569 © TÜB‹TAK 563 Received: December 06, 1999 Department of Biology, Faculty of Science,