title: Companding technique for high dynamic range measurements using Gafchromic films.
abstract: OBJECTIVE
  To introduce a methodology to perform dose measurements using Gafchromic films which can span several decades of dose levels.
  
  
  METHODS
  The technique is based on a rescaling approach using different films irradiated at different dose levels. This is combined with a registration protocol correcting positioning and scaling factors for each film. The methodology is validated using TLD's for out-of-field doses. Furthermore, two examples are provided using the technique to characterize small sized radiosurgery cones and compared with measurements made with a pinpoint chamber.
  
  
  RESULTS
  Excellent agreement with TLD, planning systems and measurement was found. The superior resolution of the film technique was apparent.
  
  
  CONCLUSIONS
  The authors have introduced a new technique allowing users to quantify very low doses in conjunction with commissioning measurements. The use of film also provides 2D information on beam characteristics in high resolution measurements.
authors.affiliation: Department of Experimental Radiotherapy, Catholic University of Leuven, Leuven, Belgium B-3000. frank.vandenheuvel@uz.kuleuven.ac.be
authors.forename: Frank
authors.initials: F
authors.lastname: Van den Heuvel
authors.forename: Wouter
authors.initials: W
authors.lastname: Crijns
authors.forename: Gilles
authors.initials: G
authors.lastname: Defraene
mesh_terms: D000465:Algorithms; D044962:Data Compression / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005373:Film Dosimetry / Q000295:instrumentation*; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity