title: Characterization of calibration curves and energy dependence GafChromic™ XR-QA2 model based radiochromic film dosimetry system.
abstract: OBJECTIVE
  The authors investigated the energy response of XR-QA2 GafChromic™ film over a broad energy range used in diagnostic radiology examinations. The authors also made an assessment of the most suitable functions for both reference and relative dose measurements.
  
  
  METHODS
  Pieces of XR-QA2 film were irradiated to nine different values of air kerma in air, following reference calibration of a number of beam qualities ranging in HVLs from 0.16 to 8.25 mm Al, which corresponds to effective energy range from 12.7 keV to 56.3 keV. For each beam quality, the authors tested three functional forms (rational, linear exponential, and power) to assess the most suitable function by fitting the delivered air kerma in air as a function of film response in terms of reflectance change. The authors also introduced and tested a new parameter χ = netΔR·e(m netΔR) that linearizes the inherently nonlinear response of the film.
  
  
  RESULTS
  The authors have found that in the energy range investigated, the response of the XR-QA2 based radiochromic film dosimetry system ranges from 0.222 to 0.420 in terms of netΔR at K(air)(air) = 8 cGy. For beam qualities commonly used in CT scanners (4.03-8.25 mm Al), the variation in film response (netΔR at K(air)(air) = 8 cGy) amounts to ± 5%, while variation in K(air)(air) amounts to ± 14%.
  
  
  CONCLUSIONS
  Results of our investigation revealed that the use of XR-QA2 GafChromic™ film is accompanied by a rather pronounced energy dependent response for beam qualities used for x-ray based diagnostic imaging purposes. The authors also found that the most appropriate function for the reference radiochromic film dosimetry would be the power function, while for the relative dosimetry one may use the exponential response function that can be easily linearized.
authors.affiliation: Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada.
authors.forename: Nada
authors.initials: N
authors.lastname: Tomic
authors.affiliation: Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada.
authors.forename: Chrystian
authors.initials: C
authors.lastname: Quintero
authors.affiliation: Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Whiting
authors.affiliation: Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada.
authors.forename: Saad
authors.initials: S
authors.lastname: Aldelaijan
authors.affiliation: Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada.
authors.forename: Hamed
authors.initials: H
authors.lastname: Bekerat
authors.affiliation: Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada.
authors.forename: LiHeng
authors.initials: L
authors.lastname: Liang
authors.affiliation: Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada.
authors.forename: François
authors.initials: F
authors.lastname: DeBlois
authors.affiliation: Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada.
authors.forename: Jan
authors.initials: J
authors.lastname: Seuntjens
authors.affiliation: Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada.
authors.forename: Slobodan
authors.initials: S
authors.lastname: Devic
mesh_terms: D000388:Air; D002138:Calibration; D005373:Film Dosimetry / Q000295:instrumentation* / Q000379:methods*; D017711:Nonlinear Dynamics; D014962:X-Ray Film