Abstract

The aim of this work was to characterized by means of Monte Carlo simulation, the radiation field produced by a kilovoltage cone-beam computed tomography (CBCT) unit integrated into the Elekta Synergy linear accelerator. The work was carried out using the Monte Carlo EGSnrc/BEAMnrc. Eight collimator cassettes were simulated. The simulation was based on technical specifications and target geometric details of the X-ray tube and filters provided by Elekta (Crawley, UK) under a confidentiality agreement. Were obtained spectral distributions, fluence profiles, and percentage depth doses curves of each simulated cassettes. Remarkable results: a) an increase in the average energy with increasing FOV (for the same collimator aperture), b) 95% of the bremsstrahlung photons generated in the
target are absorbed by the filtration cone, c) of the 5% coming out from the system, 90% did not suffer from any interaction, neither with filters nor collimators and d) fluences profiles (maximum for cassettes comprising the largest FOV) are consistent with a pronounced heel effect originating appreciable differences in the surface dose.

Keywords

• Cone Beam CT (CBCT).
• Monte Carlo simulation.
• X-ray tube.