en Radiation Biology Radiation Biology تحقيق بديع Original Research <div style="text-align: justify;">Background: This study aims to calculate the air-kerma strength (S_K), the dose rate constant (&and;) and the dose rate profiles of a Gammamed 12i Ir-192 source by using the Monte Carlo technique and to compare the dose rate values with those calculated by the Abacus HDR treatment planning system (TPS). Materials and Methods: Air-kerma strength (in units of U; 1 U= &mu;Gy m² h^-1) and the dose rate constant (&and;) of a Gammamed 12i Ir-192 source were computed with the Monte Carlo-based code MCNP. For a single dwell position, profiles of dose rate per air kerma rate strength (in unit of U) along the x axis were obtained with MCNP and compared with data from the Abacus TPS at y=0, 1, and 2 cm. Results: The air-kerma strength and the dose rate constant of the source were calculated to 9.98&times;10^-8 U and 1.106 cGy h^-1 U^-1, respectively. The maximum dose differences between MCNP and TPS along the x axis were found to be 1.3, 3.7 and 5.4% at distances more than 1 cm away from the source center for y= 0, 1 and 2 cm planes, respectively. Conclusion: The dose rate profiles calculated with MCNP and by the TPS show good agreement except for points located beyond the tip of the source.<br> &nbsp;</div> Monte Carlo, high dose rate brachytherapy, Ir-192. 241 249 http://ijrr.com/browse.php?a_code=A-10-1-672&slc_lang=en&sid=1 H. Acun acunhediye@yahoo.com 7900319475328460015480 7900319475328460015480 Yes Harran University, Faculty of Medicine, Department of Biophysics, Osmanbey Campus, 63300 Sanliurfa, Turkey A. Bozkurt 7900319475328460015481 7900319475328460015481 No Akdeniz University, Faculty of Engineering, Department of Biomedical Engineering, Antalya, Turkey G. Kemikler 7900319475328460015482 7900319475328460015482 No Istanbul University, Institute of Oncology, Department of Medical Physics, 34390 Capa, Istanbul, Turkey