title: Dosimetry audit for a multi-centre IMRT head and neck trial.
abstract: OBJECTIVE
  PARSPORT was a multi-centre randomised trial in the UK which compared Intensity-Modulated Radiotherapy (IMRT) and conventional radiotherapy (CRT) for patients with head and neck cancer. The dosimetry audit goals were to verify the plan delivery in participating centres, ascertain what tolerances were suitable for head and neck IMRT trials and develop an IMRT credentialing program.
  
  
  METHODS
  Centres enrolling patients underwent rigorous quality assurance before joining the trial. Following this each centre was visited for a dosimetry audit, which consisted of treatment planning system tests, fluence verification films, combined field films and dose point measurements.
  
  
  RESULTS
  Mean dose point measurements were made at six centres. For the primary planning target volume (PTV) the differences with the planned values for the IMRT and CRT arms were -0.6% (1.8% to -2.4%) and 0.7% (2.0% to -0.9%), respectively. Ninety-four percent of the IMRT fluence films for individual fields passed gamma criterion of 3%/3mm and 75% of the films for combined fields passed gamma criterion 4%/3mm (no significant difference between dynamic delivery and step and shoot delivery).
  
  
  CONCLUSIONS
  This audit suggests that a 3% tolerance could be applied for PTV point doses. For dose distributions tolerances of 3%/3mm on individual fields and 4%/3mm for combined fields are proposed for multi-centre head and neck IMRT trials.
authors: Department of Physics, Royal Marsden NHS Foundation Trust, London, UK. catharine.clark@rmh.nhs.uk
authors: Catharine H
authors: CH
authors: Clark
authors: Vibeke Nordmark
authors: VN
authors: Hansen
authors: Hannah
authors: H
authors: Chantler
authors: Craig
authors: C
authors: Edwards
authors: Hayley V
authors: HV
authors: James
authors: Gareth
authors: G
authors: Webster
authors: Elizabeth A
authors: EA
authors: Miles
authors: M Teresa
authors: MT
authors: Guerrero Urbano
authors: Shree A
authors: SA
authors: Bhide
authors: A Margaret
authors: AM
authors: Bidmead
authors: Christoper M
authors: CM
authors: Nutting
mesh_terms: D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008485:Medical Audit; D008875:Middle Aged; D009367:Neoplasm Staging; D011446:Prospective Studies; D011786:Quality Control; D011836:Radiation Tolerance; D011859:Radiography; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012307:Risk Factors; D016896:Treatment Outcome