title: IMRT credentialing for prospective trials using institutional virtual phantoms: results of a joint European Organization for the Research and Treatment of Cancer and Radiological Physics Center project.
abstract: OBJECTIVE
  Intensity-modulated radiotherapy (IMRT) credentialing for a EORTC study was performed using an anthropomorphic head phantom from the Radiological Physics Center (RPC; RPC(PH)). Institutions were retrospectively requested to irradiate their institutional phantom (INST(PH)) using the same treatment plan in the framework of a Virtual Phantom Project (VPP) for IMRT credentialing.
  
  
  METHODS
  CT data set of the institutional phantom and measured 2D dose matrices were requested from centers and sent to a dedicated secure EORTC uploader. Data from the RPC(PH) and INST(PH) were thereafter centrally analyzed and inter-compared by the QA team using commercially available software (RIT; ver.5.2; Colorado Springs, USA).
  
  
  RESULTS
  Eighteen institutions participated to the VPP. The measurements of 6 (33%) institutions could not be analyzed centrally. All other centers passed both the VPP and the RPC ±7%/4 mm credentialing criteria. At the 5%/5 mm gamma criteria (90% of pixels passing), 11(92%) as compared to 12 (100%) centers pass the credentialing process with RPC(PH) and INST(PH) (p = 0.29), respectively. The corresponding pass rate for the 3%/3 mm gamma criteria (90% of pixels passing) was 2 (17%) and 9 (75%; p = 0.01), respectively.
  
  
  CONCLUSIONS
  IMRT dosimetry gamma evaluations in a single plane for a H&N prospective trial using the INST(PH) measurements showed agreement at the gamma index criteria of ±5%/5 mm (90% of pixels passing) for a small number of VPP measurements. Using more stringent, criteria, the RPC(PH) and INST(PH) comparison showed disagreement. More data is warranted and urgently required within the framework of prospective studies.
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Villigen CH-5232, Switzerland. damien.weber@psi.ch.
authors.forename: Damien C
authors.initials: DC
authors.lastname: Weber
authors.forename: Veronique
authors.initials: V
authors.lastname: Vallet
authors.forename: Andrea
authors.initials: A
authors.lastname: Molineu
authors.forename: Christos
authors.initials: C
authors.lastname: Melidis
authors.forename: Vanda
authors.initials: V
authors.lastname: Teglas
authors.forename: Suzanne
authors.initials: S
authors.lastname: Naudy
authors.forename: Raphael
authors.initials: R
authors.lastname: Moeckli
authors.forename: David S
authors.initials: DS
authors.lastname: Followill
authors.forename: Coen W
authors.initials: CW
authors.lastname: Hurkmans
mesh_terms: D002986:Clinical Trials as Topic; D003406:Credentialing; D006257:Head / Q000528:radiation effects*; D006801:Humans; D015337:Multicenter Studies as Topic; D019047:Phantoms, Imaging; D011446:Prospective Studies; D011785:Quality Assurance, Health Care; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D016032:Randomized Controlled Trials as Topic; D012189:Retrospective Studies; D012984:Software