Monte Carlo modeling of the Elekta Versa HD and patient dose calculation with EGSnrc/BEAMnrc

Abstract

Introduction: Numerous studies have proven the Monte Carlo method to be an accurate means of dose calculation. Although there are several commercial Monte Carlo treatment planning systems (TPSs), some clinics may not have access to these resources.We present a method for routine,independent patient dose calculations from treatment plans generated in a commercial TPS with our own Monte Carlo model using free, open-source software. Materials and methods: A model of the Elekta Versa HD linear accelerator was developed using the EGSnrc codes. A MATLAB script was created to take clinical patient plans and convert the DICOM RTP files into a format usable by EGSnrc. Ten patients' treatment plans were exported from the Monaco TPS to be recalculated using EGSnrc. Treatment simulations were done in BEAMnrc, and doses were calculated using Source 21 in DOSXYZnrc. Results were compared to patient plans calculated in the Monaco TPS and evaluated in Verisoft with a gamma criterion of 3%/2 mm. Results: Our Monte Carlo model was validated within 1%/1-mm accuracy of measured percent depth doses and profiles. Gamma passing rates ranged from 82.1% to 99.8%, with 7 out of 10 plans having a gamma pass rate over 95%. Lung and prostate patients showed the best agreement with doses calculated in Monaco. All statistical uncertainties in DOSXYZnrc were less than 3.0%. Conclusion: A Monte Carlo model for routine patient dose calculation was successfully developed and tested. This model allows users to directly recalculate DICOM RP files containing patients' plans that have been exported from a commercial TPS.

Monte Carlo modeling of the 160 MLC on the Siemens Artiste linac and IMRT dose calculations with MCNPX

“…For all simulations, the cut-off energies of electron (ECUT) and photon (PCUT) were de ned 0.5 MeV and 0.01 MeV, respectively. These adjustments were supported by several investigators [33][34][35].…”

“…The few failed points are mainly related to the surface area, the edge of some segments and the interface between inhomogeneous regions. As mentioned by Paschal et al, the failed points within the surface area can be attributed to not considering the presence of thermoplastic mask and head supports in TPS dose calculations [34]. About the failures at the edge of some segments, the MLC opening adjustments might be slightly different between MC simulations and the TPS modelling.…”

“…Thus, several researchers have modelled various linac machines using MC simulation. For these simulations, general purpose MC software like EGSnrc [33][34][35], GEANT4 [36][37][38][39], PENELOPE [40][41][42], MCNP [43][44][45][46], … have been widely used [47][48][49][50].…”