title: Definition of parameters for quality assurance of flattening filter free (FFF) photon beams in radiation therapy.
abstract: OBJECTIVE
  Flattening filter free (FFF) beams generated by medical linear accelerators have recently started to be used in radiotherapy clinical practice. Such beams present fundamental differences with respect to the standard filter flattened (FF) beams, making the generally used dosimetric parameters and definitions not always viable. The present study will propose possible definitions and suggestions for some dosimetric parameters for use in quality assurance of FFF beams generated by medical linacs in radiotherapy.
  
  
  METHODS
  The main characteristics of the photon beams have been analyzed using specific data generated by a Varian TrueBeam linac having both FFF and FF beams of 6 and 10 MV energy, respectively.
  
  
  RESULTS
  Definitions for dose profile parameters are suggested starting from the renormalization of the FFF with respect to the corresponding FF beam. From this point the flatness concept has been translated into one of "unflatness" and other definitions have been proposed, maintaining a strict parallelism between FFF and FF parameter concepts.
  
  
  CONCLUSIONS
  Ideas for quality controls used in establishing a quality assurance program when introducing FFF beams into the clinical environment are given here, keeping them similar to those used for standard FF beams. By following the suggestions in this report, the authors foresee that the introduction of FFF beams into a clinical radiotherapy environment will be as safe and well controlled as standard beam modalities using the existing guidelines.
authors.affiliation: Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona CH-6500, Switzerland. afc@iosi.ch
authors.forename: A
authors.initials: A
authors.lastname: Fogliata
authors.forename: R
authors.initials: R
authors.lastname: Garcia
authors.forename: T
authors.initials: T
authors.lastname: Knoos
authors.forename: G
authors.initials: G
authors.lastname: Nicolini
authors.forename: A
authors.initials: A
authors.lastname: Clivio
authors.forename: E
authors.initials: E
authors.lastname: Vanetti
authors.forename: C
authors.initials: C
authors.lastname: Khamphan
authors.forename: L
authors.initials: L
authors.lastname: Cozzi
mesh_terms: D002138:Calibration; D017785:Photons / Q000627:therapeutic use*; D011786:Quality Control; D011874:Radiometry; D016634:Radiosurgery; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided