title: A comparison of the quality assurance of four dosimetric tools for intensity modulated radiation therapy.
abstract: BACKGROUND
  This study was designed to compare the quality assurance (QA) results of four dosimetric tools used for intensity modulated radiation therapy (IMRT) and to suggest universal criteria for the passing rate in QA, irrespective of the dosimetric tool used.
  
  
  METHODS
  Thirty fields of IMRT plans from five patients were selected, followed by irradiation onto radiochromic film, a diode array (Mapcheck), an ion chamber array (MatriXX) and an electronic portal imaging device (EPID) for patient-specific QA. The measured doses from the four dosimetric tools were compared with the dose calculated by the treatment planning system. The passing rates of the four dosimetric tools were calculated using the gamma index method, using as criteria a dose difference of 3% and a distance-to-agreement of 3 mm.
  
  
  RESULTS
  The QA results based on Mapcheck, MatriXX and EPID showed good agreement, with average passing rates of 99.61%, 99.04% and 99.29%, respectively. However, the average passing rate based on film measurement was significantly lower, 95.88%. The average uncertainty (1 standard deviation) of passing rates for 6 intensity modulated fields was around 0.31 for film measurement, larger than those of the other three dosimetric tools.
  
  
  CONCLUSIONS
  QA results and consistencies depend on the choice of dosimetric tool. Universal passing rates should depend on the normalization or inter-comparisons of dosimetric tools if more than one dosimetric tool is used for patient specific QA.
authors.affiliation: Department of Bio-Convergence Engineering, Korea University, Seoul, Korea ; Proton Therapy Center, National Cancer Center, Goyang, Korea.
authors.forename: Jaeman
authors.initials: J
authors.lastname: Son
authors.affiliation: Department of Bio-Convergence Engineering, Korea University, Seoul, Korea ; Department of Radiation Oncology, Ilsan Hospital, Goyang, Korea.
authors.forename: Taesung
authors.initials: T
authors.lastname: Baek
authors.affiliation: Department of Bio-Convergence Engineering, Korea University, Seoul, Korea ; Department of Radiation Oncology, Sun Hospital, Daejeon, Korea.
authors.forename: Boram
authors.initials: B
authors.lastname: Lee
authors.affiliation: Proton Therapy Center, National Cancer Center, Goyang, Korea.
authors.forename: Dongho
authors.initials: D
authors.lastname: Shin
authors.affiliation: McLaren Proton Therapy Center, Karmanos Cancer Institute, Flint, MI, USA.
authors.forename: Sung Yong
authors.initials: SY
authors.lastname: Park
authors.affiliation: Proton Therapy Center, National Cancer Center, Goyang, Korea.
authors.forename: Jeonghoon
authors.initials: J
authors.lastname: Park
authors.affiliation: Proton Therapy Center, National Cancer Center, Goyang, Korea.
authors.forename: Young Kyung
authors.initials: YK
authors.lastname: Lim
authors.affiliation: Proton Therapy Center, National Cancer Center, Goyang, Korea.
authors.forename: Se Byeong
authors.initials: SB
authors.lastname: Lee
authors.affiliation: Proton Therapy Center, National Cancer Center, Goyang, Korea.
authors.forename: Jooyoung
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Bio-Convergence Engineering, Korea University, Seoul, Korea.
authors.forename: Myonggeun
authors.initials: M
authors.lastname: Yoon
keywords: dosimetric tool; gamma index; intensity modulated radiation therapy; quality assurance