title: Gafchromic film dosimetry: four years experience using FilmQA Pro software and Epson flatbed scanners.
abstract: OBJECTIVE
  s: To assess performance of FilmQA Pro software for pre-treatment patient-specific quality assurance (QA), using radiochromic films and two commercial flatbed scanners. To evaluate a novel multichannel approach compared to the classical red channel evaluation.
  
  
  METHODS
  Patient films (mostly EBT2 films, one box of EBT3) were digitalized using successively two flatbed scanners: the A4-size Epson V750 and the A3-size Epson 10000XL. Prior to patient dose verification, basic characteristics of films and scanners were investigated. Patient films were analyzed using FilmQA Pro software, which enables to use the signal from all three colour channels (Red, Green, Blue).
  
  
  RESULTS
  Compared to the red channel evaluation, multichannel evaluation presents better passing rates with regard to local gamma index. As expected, we obtained better results using A3-size scanner compared to A4-size scanner, especially when considering large region of interest. An observation of great interest was made for both scanners: after intensive use, a tilting in the blue transmittance profiles appeared in the lamp direction, making multichannel analysis unsuitable for accurate dose evaluation.
authors.affiliation: Service de Radiothérapie, Centre Hospitalier Universitaire de Liège, Domaine Universitaire du Sart Tilman, B35, 4000 Liège, Belgium. Electronic address: mmathot@chu.ulg.ac.be.
authors.forename: M
authors.initials: M
authors.lastname: Mathot
authors.affiliation: Service de Radiothérapie, Centre Hospitalier Universitaire de Liège, Domaine Universitaire du Sart Tilman, B35, 4000 Liège, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Sobczak
authors.affiliation: Service de Radiothérapie, Centre Hospitalier Universitaire de Liège, Domaine Universitaire du Sart Tilman, B35, 4000 Liège, Belgium.
authors.forename: M-T
authors.initials: MT
authors.lastname: Hoornaert
mesh_terms: D002138:Calibration; D003201:Computers; D004307:Dose-Response Relationship, Radiation; D005373:Film Dosimetry / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D011786:Quality Control; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation / Q000379:methods*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D015203:Reproducibility of Results; D012984:Software
keywords: Flatbed scanners; GAFCHROMIC; Multichannel correction