title: Application of Gafchromic EBT2 film for intraoperative radiation therapy quality assurance.
abstract: OBJECTIVE
  Intraoperative radiation therapy (IORT) using electron beam is commonly done by mobile dedicated linacs that have a variable range of electron energies. This paper focuses on the evaluation of the EBT2 film response in the green and red colour channels for IORT quality assurance (QA).
  
  
  METHODS
  The calibration of the EBT2 films was done in two ranges; 0-8 Gy for machine QA by red channel and 8-24 Gy for patient-specific QA by green channel analysis. Irradiation of calibration films and relative dosimetries were performed in a water phantom. To evaluate the accuracy of the film response in relative dosimetry, gamma analysis was used to compare the results of the Monte Carlo simulation and ionometric dosimetry. Ten patients with early stage breast cancer were selected for in-vivo dosimetry using the green channel of the EBT2 film.
  
  
  RESULTS
  The calibration curves were obtained by linear fitting of the green channel and a third-order polynomial function in the red channel (R2=0.99). The total dose uncertainty was up to 4.2% and 4.7% for the red and green channels, respectively. There was a good agreement between the relative dosimetries of films by the red channel, Monte Carlo simulations and ionometric values. The mean dose difference of the in-vivo dosimetry by green channel of this film and the expected values was about 1.98% ± 0.75.
  
  
  CONCLUSIONS
  The results of this study showed that EBT2 film can be considered as an appropriate tool for machine and patient-specific QA in IORT.
authors.affiliation: Department of Medical Physics, Tehran University of Medical Science, Poursina St, 1417614411 Tehran, Iran.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Robatjazi
authors.affiliation: Department of Medical Physics, Iran University of Medical Science, Hemmat Exp. Way, 14496141525 Tehran, Iran. Electronic address: SRMahdavi@Hotmail.com.
authors.forename: Seied Rabi
authors.initials: SR
authors.lastname: Mahdavi
authors.affiliation: Department of Medical Physics, Tehran University of Medical Science, Poursina St, 1417614411 Tehran, Iran.
authors.forename: Abbas
authors.initials: A
authors.lastname: Takavr
authors.affiliation: Department of Radiation Medicine, Shahid Beheshti University, Daneshjoo St, Velenjak, 1983963113 Tehran, Iran.
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Baghani
mesh_terms: D002138:Calibration; D004583:Electrons; D005373:Film Dosimetry; D006801:Humans; D007432:Intraoperative Period; D009010:Monte Carlo Method; D011786:Quality Control; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted
keywords: Gafchromic EBT2 film; IORT; Quality assurance