title: Clinical implementation of volumetric intensity-modulated arc therapy (VMAT) with ERGO++.
abstract: OBJECTIVE
  Volumetric modulated arc therapy (VMAT) has the potential to deliver dose distributions comparable to the established intensity-modulated radiotherapy techniques for a multitude of target paradigms. Prior to implementing VMAT into their clinical routine in December 2008, the authors evaluated the dose calculation/delivery accuracy of 24 sample VMAT plans (prostate and anal cancer target paradigms) with film and ionization dosimetry. After the start of the clinical program, in vivo measurements with a rectal probe were performed.
  
  
  METHODS
  The VMAT plans were generated by the treatment-planning system (TPS) ERGO++ (Elekta, Crawley, UK) and transferred to a phantom. Film dosimetry was performed with Kodak EDR2 films, and evaluated with dose profiles and gamma-index analysis. Appropriate ionization chambers were used for absolute dose measurements in the phantom and for in vivo measurements. The ionization chamber was used with localization of the measurement volume based on positioning cone-beam computed tomography.
  
  
  RESULTS
  Plans were transferred from ERGO++ to the record and verify (R&V) system/linear accelerator (linac). The absolute dose deviations recorded with the ionization chamber were 1.74% +/- 1.62% across both indications. The gamma-index analysis of the film dosimetry showed no deviation > 3%/3 mm in the high-dose region. On in vivo measurements, a deviation between calculation and measurement of 2.09% +/- 2.4% was recorded, when the chamber was successfully positioned in the high-dose region.
  
  
  CONCLUSIONS
  VMAT plans can be planned and treated reproducibly in high quality after the commissioning of the complete delivery chain consisting of TPS, R&V system and linac. The results of the individual plan verification meet the commonly accepted requirements. The first in vivo measurements confirm the reproducible precision of the delivered dose during clinical treatments.
authors.affiliation: Department of Radiation Oncology of the University Medical Center Mannheim, University of Heidelberg. wolff.dirk@gmx.de
authors.forename: Dirk
authors.initials: D
authors.lastname: Wolff
authors.forename: Florian
authors.initials: F
authors.lastname: Stieler
authors.forename: Brigitte
authors.initials: B
authors.lastname: Hermann
authors.forename: Katharina
authors.initials: K
authors.lastname: Heim
authors.forename: Sven
authors.initials: S
authors.lastname: Clausen
authors.forename: Jens
authors.initials: J
authors.lastname: Fleckenstein
authors.forename: Martin
authors.initials: M
authors.lastname: Polednik
authors.forename: Volker
authors.initials: V
authors.lastname: Steil
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
authors.forename: Frank
authors.initials: F
authors.lastname: Lohr
mesh_terms: D005373:Film Dosimetry; D006801:Humans; D008297:Male; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*