title: Commissioning Siemens Virtual Wedges in the Oncentra MasterPlan treatment planning system using Gafchromic EBT film.
abstract: OBJECTIVE
  Virtual Wedges were introduced in Siemens LINACs to improve the treatment workflow. The aim of the present work is the validation of dose calculation by MasterPlan-Oncentra treatment planning system for virtual wedged beams.
  
  
  METHODS
  The Oncor Siemens accelerator installed in the authors' department produces 6 and 15 MV photon beams. At first, the consistency of VW LINAC production was tested and the EBT film measuring method was verified. This method is based on the scanner uniformity correction and absolute dose calibration as reported in literature. Then, the measured and calculated wedge factors and beam profiles are compared. For 15 degrees, 30 degrees, 45 degrees, and 60 degrees wedge angles, the wedge factors for different field sizes were measured by an ionization chamber and the dose profiles were acquired by Gafchromic EBT film. Both types of measurements were collected in isocentric condition.
  
  
  RESULTS
  The comparison between measured and calculated VW factors shows discrepancies that increase with field size and angle. The OTP Enhanced algorithm produces better agreement with measurements than the Classic one, with improvement overall visible for large angles. The agreement between measured and planned beam profiles is within limits reported by the ESTRO Booklet No. 7 in terms of confidence limits.
  
  
  CONCLUSIONS
  The MasterPlan-Oncentra treatment planning system determines wedge factors and VW profiles within the requested accuracy in the majority of treatment conditions. For big field dimensions and wedge angle, wedge factor accordance was worse, but it may be increased with an improvement of the LINAC dosimetric board calibration.
authors.affiliation: Department of Medical Physics, Veneto Institute of Oncology IOV-IRCCS, 35128 Padua, Italy. aliceferretti@hotmail.com
authors.forename: A
authors.initials: A
authors.lastname: Ferretti
authors.forename: F
authors.initials: F
authors.lastname: Simonato
authors.forename: R
authors.initials: R
authors.lastname: Zandonà
authors.forename: S
authors.initials: S
authors.lastname: Reccanello
authors.forename: R
authors.initials: R
authors.lastname: Fabbris
mesh_terms: D005373:Film Dosimetry / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D014584:User-Computer Interface