title: An inter-centre quality assurance network for IMRT verification: results of the ESTRO QUASIMODO project.
abstract: OBJECTIVE
  IMRT necessitates extension of existing inter-centre quality assurance programs due to its increased complexity. We assessed the feasibility of an inter-centre verification method for different IMRT techniques.
  
  
  METHODS
  Eight European radiotherapy institutions of the QUASIMODO network, have designed an IMRT plan for a horseshoe-shaped PTV surrounding a cylindrical OAR in a simplified pelvic phantom. All centres applied common plan objectives but used their own equipment for planning and delivery. They verified the delivery of this plan according to a common protocol with radiographic film and ionisation chamber measurements. The irradiated films, the results of the ionisation chamber measurements and the computed dose distributions were sent to one analysis centre that compared the measured and computed dose distributions with the gamma method and composite dose-area histograms.
  
  
  RESULTS
  4% (relative to the prescribed dose) and 3mm (distance-to-agreement) were decided feasible gamma criteria. The composite dose-area histograms showed a maximum local deviation of 3.5% in the mean dose of the PTV and 5% in the OAR. Systematic differences could be identified, and in some cases explained.
  
  
  CONCLUSIONS
  This multi-centre dosimetric verification study demonstrated both the feasibility of a multi-centre quality assurance network to evaluate any IMRT planning and delivery system combination, as well as the validity of the methodology involved.
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Gent, Belgium. sifie.gillis@skynet.be
authors.forename: Sofie
authors.initials: S
authors.lastname: Gillis
authors.forename: Carlos
authors.initials: C
authors.lastname: De Wagter
authors.forename: Joerg
authors.initials: J
authors.lastname: Bohsung
authors.forename: Bruce
authors.initials: B
authors.lastname: Perrin
authors.forename: Peter
authors.initials: P
authors.lastname: Williams
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Mijnheer
mesh_terms: D019058:Community Networks; D019583:Dose Fractionation, Radiation; D006801:Humans; D008962:Models, Theoretical; D009369:Neoplasms / Q000532:radiotherapy; D011785:Quality Assurance, Health Care / Q000458:organization & administration*; D011874:Radiometry; D011878:Radiotherapy / Q000592:standards*; D015203:Reproducibility of Results; D014584:User-Computer Interface