exploration of monte carlo simulation from a case study of particle transport in the gamma knife perfexion™ machine

Introduction: gamma knife perfexion™ delivers 192 cobalt-60 sources to the focal point (isocenter), and the patient is fixed using a stereotactic frame. in conformal techniques, the width of the penumbra resulting in an out-of-field dose of normal tissue adjacent to the tumor must be accurately determined. the purpose of this study was to calculate the penumbra widths of a single beam and 192 beams for different collimator sizes of the gamma knife perfexion™ using the beamnrc/dosxyznrc monte carlo simulation code and compare the results with ebt3 film dosimetry data.material and methods: to investigate the physical penumbra width (80-20%), the single beam and 192 beam profiles were obtained using the dosxyznrc code and ebt3 films located at the isocenter point in a spherical solid water phantom with a diameter of 160 mm. results: the results showed that the gamma passing rate (gpr) value for all collimator sizes has a value above 97%. the single-beam penumbra widths obtained from simulation data for 4, 8, and 16 mm collimator sizes along the x-axis were 0.75, 0.77, and 0.87 mm, respectively. the data for 192 beams obtained from the simulation were 2.60, 4.80, and 8.70 mm along the x-axis.conclusion: the differences between measured and simulated penumbra widths are in an acceptable range. however, for more precise measurement in the penumbra region with a high dose gradient, a monte carlo simulation is recommended.