RPD Volume 168 Issue 4 March 2016 comments 5

Monte Carlo Simulation of secondary radiation exposure from high-energy photon therapy using an anthropomorphic phantom Ab Stract

The development of intensity-modulated radiotherapy treatments delivering large amounts of monitor units (MUs) recently RA Ised concern about higher risks for secondary malignancies. In this study, optimised combinations of several variance reduction techniques (vrts) has been implemented in order to AC Hieve a high precision in Monte Carlo (MC) radiation transport simulations and the calculation of In-and Out-of-field Pho ton and neutron dose-equivalent distributions in an anthropomorphic phantom using MCNPX, v.2.7. The computer model included a Varian Clinac 2100C treatment Head and a high-resolution head phantom. By means of the applied vrts, a relative uncertainty for the photon dose-equivalent distribution of <1% In-field and 1 5% average over the rest of the Phantom could is obtained. Neutron dose equivalent, caused by photonuclear reactions in the linear accelerator components at photon energies of appro Ximately >8 MeV, has been calculated. Relative uncertainty, CalculaTed for each voxel, could is kept below 5 in average over all voxels of the Phantom. Thus, a very detailed neutron dose distribution could be obtained. The achieved precision now allows a far better estimation of both photon and especially neutron doses Out-of-field, where Neutrons can become the predominant component of secondary radiation.

RPD Volume 168 Issue 4 March 2016 comments 5