Application of volumetric modulated arc therapy (VMAT) in a dual-vendor environment

BACKGROUND AND PURPOSE: The purpose of this study was to assess plan quality and treatment time achievable with the new VMAT optimization tool implemented in the treatment planning system Oncentra MasterPlan(® )as compared to IMRT for Elekta SynergyS(® )linear accelerators. MATERIALS AND METHODS: VMAT was implemented on a SynergyS(® )linear accelerator (Elekta Ltd., Crawley, UK) with Mosaiq(® )record and verify system (IMPAC Medical Systems, Sunnyvale, CA) and the treatment planning system Oncentra MasterPlan(® )(Nucletron BV, Veenendaal, the Netherlands). VMAT planning was conducted for three typical target types of prostate cancer, hypopharynx/larynx cancer and vertebral metastases, and compared to standard IMRT with respect to plan quality, number of monitor units (MU), and treatment time. RESULTS: For prostate cancer and vertebral metastases single arc VMAT led to similar plan quality as compared to IMRT. For treatment of the hypopharynx/larynx cancer, a second arc was necessary to achieve sufficient plan quality. Treatment time was reduced in all cases to 35% to 43% as compared to IMRT. Times required for optimization and dose calculation, however, increased by a factor of 5.0 to 6.8. CONCLUSION: Similar or improved plan quality can be achieved with VMAT as compared to IMRT at reduced treatment times but increased calculation times.