Monte Carlo Evaluation of Gamma Knife Dose Profile in Real Brain Phantom

Introduction: the gamma knife system is designed solely for non-invasive treatment of brain disorders, and it benefits from stereotactic surgical techniques. dose calculations required in the system are performed by gammaplan code; in this code, brain tissue is considered uniform. in the present study, we evaluated the effect of gamma knife system on the obtained dose through simulating a real human brain phantom. materials and methods: in this study, a monte carlo simulation code (mcnpx2.7) was employed to simulate gamma knife system. brain tissue equivalent snyder phantom and combinations were considered according to international commission on radiological units (icru)-44 report. results: to ensure accuracy of the simulations, patient’s head was modeled by a spherical water phantom. at this point, the dosimetry parameters were compared with those obtained by the monte carlo code egs4 and good consistency was observed (less than 7% difference). at the next stage, the above dosimetry parameters were compared with those obtained experimentally by polystyrene phantom and edr2 dosimetry film and improved consistency was detected (less than 0.5% difference). finally, the snyder phantom, as the human brain, was simulated. the full width at half maximum (fwhm) and penumbra decreased by 4.7% and 18%, respectively. moreover, an isocenter dose reduction of 30-40%, compared to the water phantom, was noted. conclusion: the calculation of the real phantom showed that water and polystyrene could function similarly, while evaluating dosimetry parameters in the gamma knife system; thus, water and polystyrene are not appropriate phantom matters for this purpose.