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UBC Theses and Dissertations

Validation of Monte Carlo simulation of 6 MV photon beam delivered by the Vero4DRT linear accelerator using BEAMnrc and DOSXYZnrc Rostamzadeh, Maryam


The goal of this project is to develop a Monte Carlo (MC) simulation model for the 6MV Vero4DRT platform which is a stereotactic ablative radiation therapy (SABR) medical linear accelerator. This MC model can simulate a variety of radiotherapy delivery techniques, including three-dimensional conformal radiotherapy (3DCRT), dynamic conformal arc (DCA) therapy, as well as complex treatments such as static-field step-and-shoot intensity modulated radiotherapy (sIMRT), volumetric modulated arc therapy (VMAT) and non-coplanar trajectory-based Dynamic Wave Arc (DWA) in a single MC run. Open-source Monte Carlo applications based on EGSnrc particle transport codes are used to simulate the medical linear accelerator head components (BEAMnrc). The VERO4DRT has a maximum radiation field size of 15×15 cm² at 100 cm from the source. All beam shaping is achieved with a low-transmission multileaf collimator (MLC). The moving MLC leaves are modelled using the SYNCVMLC component module in BEAMnrc. Radiation doses to patients and phantoms are simulated using DOSXYZnrc codes. Electron energy tuning is achieved by comparing measured vs simulated percentage depth doses (PDDs) for a variety of field sizes in a water phantom. Electron spot size tuning is achieved by comparing beam profiles at depths 1.5 and 10 cm for the same field sizes. MC simulations with electron beam energy of 5.9 MeV and spot size FWHM=1.9mm demonstrated the closest agreement with measurement. The differences between measurement and calculation are

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