Influence of 6 MV and 20 MV X- radiation dose rate on in vitro survive of the K-562 cell line

Background: Analysis of the survival rate of cells after irradiation with a specified dose of X-radiation might be one of the basic foundations for assessment of biological implications of ionizing radiation. Investigation of the influence of X-radiation dose rate on cells was carried out in vitro using the SF2 test. Aim: The aim of this study was to investigate the influence of X-radiation dose rate on the surviving fraction of the K-562 cell line for two photon energies of 6 MV and 20 MV. Materials/Methods: To measure the cells reaction to X-radiation of variable dose rate human leukaemic K-562 cells were used. In order to fulfil the main aim of the study, the cell line was subjected to irradiation at two different dose rates. Total dose applied at once was 2 Gy. A quantitative evaluation of cell survival rate was carried out at every step of the experiment using a clonogenic assay. Results: High dose rate at the energy of 6 MV decreased the percentage of surviving cells to 23%, while lower dose rate decreased it only to 36%. A similar effect is observed at the energy of 20 MV -namely at the higher dose rate the percentage of surviving cells is 18%, whereas at the lower one it is only 34%. Conclusions: The experiment has shown that when using a lower dose rate, the biological effect of ionizing radiation is less pronounced. However, at a higher dose rate higher radiosensitivity of cells is observed. (authors)