title: Initial investigation on the use of MR spectroscopy and micro-MRI of GAFCHROMIC EBT radiotherapy film.
abstract: OBJECTIVE
  This article presents an initial investigation of the efficacy of using 1H MRS and micro-MRI as analysis techniques for irradiated GAFCHROMIC EBT radiotherapy films.
  
  
  METHODS
  GAFCHROMIC EBT radiotherapy film was irradiated with 6 MV x rays to known doses ranging from 5 to 1000 cGy. 24 h following irradiation 1H MRS measurements were performed to access the degree of post-irradiation polymer cross-linking. 2D 1H micro-MRI experiments were also performed for film irradiations of 0 and 300 cGy.
  
  
  RESULTS
  Linear response of the 1H MRS linewidth to dose in the range from 0 to 400 cGy (R2 = 0.98) was observed. Such linearity is not seen when analyzed under conventional light analysis. The sensitivity of the film, as measured by the slope of the curve between 0 and 400 cGy, is 0.0042 +/- 0.0003 kHz/cGy, demonstrating the sensitivity of the 1H MRS technique used to analyze the film. The film saturates at a dose of approximately 900 cGy. Broadline 1H MRS provides a quantitative measure of the degree of polymerization of the film.
  
  
  CONCLUSIONS
  A quantitative measurement of the degree of polymerization of GAFCHROMIC EBT film has been presented using 1H MRS. The saturation of the film at approximately 900 cGy is corroborated by that observed with light analysis. Further MR spectroscopic experiments are needed to investigate the response of the film to dose, allowing for a better understanding of the relationship between polymer cross-linking in the active layer.
authors.affiliation: Department of Medical Physics, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5, Canada. rholly@lakeridgehealth.on.ca
authors.forename: Rick
authors.initials: R
authors.lastname: Holly
authors.forename: Brian M
authors.initials: BM
authors.lastname: Keller
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pignol
authors.forename: Claude
authors.initials: C
authors.lastname: Lemaire
authors.forename: Hartwig
authors.initials: H
authors.lastname: Peemoeller
mesh_terms: D005240:Feasibility Studies; D005373:Film Dosimetry / Q000295:instrumentation* / Q000379:methods*; D008027:Light; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011108:Polymers / Q000737:chemistry; D011522:Protons; D011829:Radiation Dosage; D011878:Radiotherapy / Q000295:instrumentation*; D012680:Sensitivity and Specificity; D014962:X-Ray Film; D014965:X-Rays
chemical_list: D011108:Polymers; D011522:Protons