title: An on-site audit system for dosimetry credentialing of intensity-modulated radiotherapy in Japanese Clinical Oncology Group (JCOG) clinical trials.
abstract: OBJECTIVE
  This study was undertaken to analyze the results of intensity-modulated radiotherapy (IMRT) dosimetry credentialing using a phantom in the Japanese Clinical Oncology Group clinical trials.
  
  
  METHODS
  All measurements were performed on-site. The IMRT phantom consisted of a phantom shell and a module. Two types of structures, including a C-shaped planning target volume (PTV) around a column-shaped organ at risk (OAR), were included in the module. Each participating institution was asked to image, plan, and treat the phantom. A prescription dose of 2Gy should cover 95% of the PTV. The plan should limit the maximum doses to the PTV and OAR to less than 110% and 60%, respectively. The pass criteria were ±3% in terms of chamber dosimetry and a difference in profile position ⩽2mm in the high-dose gradient area of film dosimetry. The positional difference was defined as the largest distance between the measured and calculated positions at doses of 60% or 80%. These tolerances were based on the Japanese Society for Radiation Oncology IMRT guidelines.
  
  
  RESULTS
  Credentialing was performed on a total of 44 treatment machines in 32 institutions from 2009 to 2015. All differences between measured and planned doses at the measurement points of the PTV were within 3%. The means±standard deviations of the positional differences were 1.0±0.4mm and 0.9±0.3mm without and with the phantom shell, respectively.
  
  
  CONCLUSIONS
  The dose differences and positional differences met the desired criteria in all institutions.
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan. Electronic address: m_nkmr@kuhp.kyoto-u.ac.jp.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Center for Cancer Control and Information Services, National Cancer Center, Tokyo, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Minemura
authors.affiliation: Department of Radiology, Koshigaya Municipal Hospital, Saitama, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ishikura
authors.affiliation: Department of Radiation Oncology, Graduate School of Medicine, Hiroshima University, Japan.
authors.forename: Teiji
authors.initials: T
authors.lastname: Nishio
authors.affiliation: Department of Oncological Radiation, Aomori Prefectural Central Hospital, Aomori, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Narita
authors.affiliation: Department of Radiation Oncology, Kindai University Faculty of Medicine, Japan.
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Nishimura
mesh_terms: D054869:Clinical Audit; D002986:Clinical Trials as Topic; D003406:Credentialing; D006801:Humans; D007564:Japan; D008495:Medical Oncology; D058958:Organs at Risk / Q000528:radiation effects; D019047:Phantoms, Imaging; D011874:Radiometry / Q000592:standards*; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000592:standards*
keywords: IMRT/VMAT; Multi-institutional clinical trials; On-site dosimetry credentialing