egsnrc/beamnrc-based monte carlo simulation of the gamma knife 4c versus mcnp code in homogeneous media

Purpose: gamma knife is applied as a superseded tool for inaccessible lesions surgery delivering a single high dose to a well-defined target through 201 small beams. monte carlo simulations can be an appropriate supplementary tool to determine dosimetric parameters in small fields due to the related dosimetry hardships.materials and methods: egsnrc/beamnrc monte carlo code was implemented to model gamma knife 4c. single channel geometry comprising stationary and helmet collimators was simulated. a point source was considered as a cylindrical cobalt source based on the simplified source channel mode. all of the 201 source channels were arranged in spherical coordinate by egsnrc/dosxyznrc code to calculate dose profiles. the simulated profiles at the isocentre point in a spherical head phantom 160 mm in diameter along three axes for 4, 8, 14, and 18 mm field sizes were compared to those obtained by another work using mcnp code.results: based on the results, the beamnrc and mcnp dose profiles matched well apart from the 18 mm profiles along x and y directions with the average gamma index of 1.36 and 1.18, respectively. beamnrc profiles for 14 and 18 mm field sizes along x and y axes were entirely flat in plateau region, whereas mcnp profiles represented variations as well as round shape. besides, considering the identical results, radioactive source can be modeled by a point source instead of cylindrical one.conclusion: thus, the egsnrc/beamnrc code is recommended to simulate gamma knife machine as it is regarded as the most accurate computer program to simulate photon and electron interactions.