Room: Exhibit Hall
Purpose: This work summarizes the experience and results of validating beam models for an Elekta Versa HD linear accelerator with a Monaco treatment planning system (TPS)
Methods: The linac was modelled in Monaco using three algorithms: Collapsed Cone (CC) and photon Monte Carlo (MC) for photon beams, and electron Monte Carlo (eMC) for electron beams. Validations were performed on measured PDDs and profiles, and for open field point doses in homogeneous and heterogeneous media. Gamma analysis for IMRT and VMAT plans, including VMAT SBRT, were performed.
Results: All PDDs and beam profiles generated by Monaco were in good agreement with measured data when evaluated in a 2%/2mm gamma analysis, with gamma index below 1 for all relevant conditions. Point doses in homogeneous water were found to be in 2% or better agreement with commissioning data in 99.5% and 98.6% of the points computed by MC and CC, respectively. For eMC in homogeneous water, all point doses were within 4% agreement, and 92% of the points were within 3% agreement. In heterogeneous media with the presence of air and cortical bone, both CC and MC yielded better than 3% agreement with ion chamber measurements. eMC yielded 3% agreement with ion chamber measurement downstream of air, and 5% agreement downstream of the bone slabs, for all electron energies except 6 MeV. For extended SSD situations, eMC calculation of point doses was within 4% of measurements for all energies except 6 MeV. In both exceptions, the 6 MeV point of measurement was on a steep dose gradient; an exact match was found within 3mm of the point. The average gamma passing rate for IMRT/VMAT plans was 98.4% (Â±1.4%) when evaluated using 3%/3mm criteria.
Conclusion: Monaco beam models for the Versa HD linac showed clinically acceptable results, and may be deployed for clinical use.