This research investigates the effects of medical radiation on human lymphocytes, focusing on chromosomal abnormalities induced by X-ray photon irradiation at energies of 6 and 10 MV. The study explores the dosedependent relationship between absorbed doses (ranging from 0.5 to 8 Gy) and the frequency of chromosomal aberrations, with dose rates varying from 5.50 to 23.08 Gy/min. A comparison with 60Co gamma radiation was conducted using standard cytogenetic methods to produce metaphases and analyze chromosomal damage. The findings revealed significant variations in aberration frequencies across different irradiation techniques, with the flattening filter-free (FFF) mode demonstrating a stronger radiobiological impact than the conventional flattening filter (FF) mode. A linear-quadratic dose-response calibration curve was constructed to determine the relative biological effectiveness (RBE) of the different radiation modalities. The average RBE values were found to be 1.28 for 60Co, 1.11 for 6 MV FFF, and ranged from 0.79 to 0.92 for 10 MV FFF. These results highlight the importance of updating biodosimetry calibration curves to account for higher radiation energies and dose rates, particularly in therapeutic contexts. The study emphasizes the need for precise biodosimetry in situations involving unintentional radiation overdoses, as accurate calibration curves are crucial for quantifying such events, especially in hypofractionated treatments.