title: Evaluation of DVH-based treatment plan verification in addition to gamma passing rates for head and neck IMRT.
abstract: OBJECTIVE
  Treatment plan verification of intensity modulated radiotherapy (IMRT) is generally performed with the gamma index (GI) evaluation method, which is difficult to extrapolate to clinical implications. Incorporating Dose Volume Histogram (DVH) information can compensate for this. The aim of this study was to evaluate DVH-based treatment plan verification in addition to the GI evaluation method for head and neck IMRT.
  
  
  METHODS
  Dose verifications of 700 subsequent head and neck cancer IMRT treatment plans were categorised according to gamma and DVH-based action levels. Fractionation dependent absolute dose limits were chosen. The results of the gamma- and DVH-based evaluations were compared to the decision of the medical physicist and/or radiation oncologist for plan acceptance.
  
  
  RESULTS
  Nearly all treatment plans (99.7%) were accepted for treatment according to the GI evaluation combined with DVH-based verification. Two treatment plans were re-planned according to DVH-based verification, which would have been accepted using the evaluation alone. DVH-based verification increased insight into dose delivery to patient specific structures increasing confidence that the treatment plans were clinically acceptable. Moreover, DVH-based action levels clearly distinguished the role of the medical physicist and radiation oncologist within the Quality Assurance (QA) procedure.
  
  
  CONCLUSIONS
  DVH-based treatment plan verification complements the GI evaluation method improving head and neck IMRT-QA.
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands; Professorship in Health Care and Nursing, Hanze University Groningen, University of Applied Sciences, Groningen, The Netherlands. Electronic address: r.visser@umcg.nl.
authors.forename: Ruurd
authors.initials: R
authors.lastname: Visser
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: David J L
authors.initials: DJ
authors.lastname: Wauben
authors.affiliation: Professorship in Health Care and Nursing, Hanze University Groningen, University of Applied Sciences, Groningen, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: de Groot
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Roel J H M
authors.initials: RJ
authors.lastname: Steenbakkers
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Henk P
authors.initials: HP
authors.lastname: Bijl
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Godart
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Aart A
authors.initials: AA
authors.lastname: van't Veld
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Langendijk
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Erik W
authors.initials: EW
authors.lastname: Korevaar
mesh_terms: D005720:Gamma Rays; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D015203:Reproducibility of Results
keywords: Action levels; Dose Volume Histogram; IMRT; Plan verification; Quality Assurance