en Radiation Biology Radiation Biology تحقيق بديع Original Research <span style="font-weight: bold">Background:</span> The purpose of this paper is to establish an easy and reliable biodosimeter protocol to evaluate the biological effects of proton beams. <span style="font-weight: bold">Materials and Methods:</span> Human peripheral blood lymphocytes were irradiated using proton beams (LET: 34.6 keV μm−1), and the chromosome aberrations induced were analyzed using cytokinesis-blocked (CB) micronucleus (MN) assay. To determine the efficiency of MN assay in estimating the doses received by 50MeV proton beams and to monitor predicted dose of victims in accidental exposure, here we have evaluated the performance of MN analysis in a simulated situation after exposure with proton beams. Peripheral lymphocytes were irradiated by 50MeV proton beams up to 6Gy and analyzed by Giemsa staining of CB MN assay. <span style="font-weight: bold">Results: </span>The detected MN was found to be a significant dose-effect curve in the manner of dose-dependent increase after exposure with proton beams <span style="font-style: italic">in vitro</span>. When plotting on a linear scale against radiation dose, the line of best fit was Y=0.004+(1.882x10^-2±9.701x10^-5) D+(1.43x10^-3±1.571x10^-5)D2. Our results show a trend towards increase of the number of MN with increasing dose. It was linear-quadratic and has a significant relationship between the frequencies of MN and dose (R2= 0.9996). The number of MN in lymphocyte that was observed in control group is 5.202±0.04/cell. <span style="font-weight: bold">Conclusion: </span>Hence, this simple protocol will be particularly useful for helping physicians to decide medical therapy for the initial treatment of victims with rapid and precise dose estimation after accidental radiation exposure. Also it has potential for use as a valuable biomarker to evaluate the biological effectiveness for cancer therapy with proton beams. Iran. J. Radiat. Res., 2011 8(4): 231-236 Human peripheral lymphocyte, biodosimetry, proton beams, dose estimation, triage. 231 236 http://ijrr.com/browse.php?a_code=A-10-1-373&slc_lang=en&sid=1 Y.J. Go 790031947532846002053 790031947532846002053 No J.H. Shin 790031947532846002054 790031947532846002054 No K.S. Jeong 790031947532846002055 790031947532846002055 No S.J. Park 790031947532846002056 790031947532846002056 No S.H. Kim 790031947532846002057 790031947532846002057 No S.Y. Ryu 790031947532846002058 790031947532846002058 No C.H. Kim 790031947532846002059 790031947532846002059 No E.J. Kim 790031947532846002060 790031947532846002060 No Ch.M. Kang 790031947532846002061 790031947532846002061 No TH. Kim thkim56@knu.ac.kr 790031947532846002062 790031947532846002062 Yes