title: Report on use of a methodology for commissioning and quality assurance of a VMAT system.
abstract: BACKGROUND
  Results of use of methodology for VMAT commissioning and quality assurance, utilizing both control point tests and dosimetric measurements are presented.
  
  
  METHODS
  A generalizable, phantom measurement approach is used to characterize the accuracy of the measurement system. Correction for angular response of the measurement system and inclusion of couch structures are used to characterize the full range gantry angles desirable for clinical plans. A dose based daily QA measurement approach is defined.
  
  
  RESULTS
  Agreement in the static vs. VMAT picket fence control point test was better than 0.5 mm. Control point tests varying gantry rotation speed, leaf speed and dose rate, demonstrated agreement with predicted values better than 1%. Angular dependence of the MatriXX array, varied over a range of 0.94-1.06, with respect to the calibration condition. Phantom measurements demonstrated central axis dose accuracy for un-modulated four field box plans was ≥2.5% vs. 1% with and without angular correction respectively with better results for VMAT (0.4%) vs. IMRT (1.6%) plans. Daily QA results demonstrated average agreement all three chambers within 0.4% over 9 month period with no false positives at a 3% threshold.
  
  
  CONCLUSIONS
  The methodology described is simple in design and characterizes both the inherit limitations of the measurement system as well at the dose based measurements that may be directly related to patient plan QA.
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota, USA. mayo.charles@mayo.edu
authors.forename: Charles
authors.initials: C
authors.lastname: Mayo
authors.forename: Luis
authors.initials: L
authors.lastname: Fong de los Santos
authors.forename: Jon
authors.initials: J
authors.lastname: Kruse
authors.forename: Charles R
authors.initials: CR
authors.lastname: Blackwell
authors.forename: Luke B
authors.initials: LB
authors.lastname: McLemore
authors.forename: Deanna
authors.initials: D
authors.lastname: Pafundi
authors.forename: Joshua
authors.initials: J
authors.lastname: Stoker
authors.forename: Michael
authors.initials: M
authors.lastname: Herman
mesh_terms: D002138:Calibration; D006801:Humans; D011785:Quality Assurance, Health Care / Q000379:methods*; D011786:Quality Control; D011879:Radiotherapy Dosage / Q000592:standards; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000592:standards*; D015203:Reproducibility of Results
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