monte carlo and experimental relative dose determination for an iridium-192 source in water phantom

background: monte carlo and experimental relative dose determination in a water phantom, due to a high dose rate (hdr) 192ir source is presented for real energy spectrum and monochromatic at 356 kev. materials and methods: the dose distribution has been calculated around the 192ir located in the center of 30 cm ×30 cm ×30 cm water phantom using mcnp4c code by monte carlo method. relative dose variation has been measured by using gafchromic rtqa along x and y axis, as well. percentage depth dose (pdd) variation along the different axis parallel and perpendicular the source were calculated. finally, f (5cm, θ|) dosimetry parameters of tg-43 protocol were determined. results: the results showed that the monte carlo method could calculate dose deposition in high gradient region, near the source, accurately. the isodose curves and dosimetric characteristics obtained for 192ir source are in good agreement with experimental results. conclusion: the isodose curves of the 192ir source were derived form dose calculation by mcnp code. also, monte carlo and experimental pdd x=2.5 mm are in good agreement, and the both results y=10 mm, in ||x [-25mm,25mm] interval were well matched. however, out of this range monte carlo result was estimated to be lower. the calculated dosimetry parameters for the source were in agreement with other results. iran. j. radiat. res., 2008 6 (1): 37-42