title: [Development of external quality control protocol for CyberKnife beams dosimetry: preliminary tests multicentre].
abstract: OBJECTIVE
  To develop an external quality control procedure for CyberKnife(®) beams. This work conducted in Nancy, has included a test protocol initially drawn by the medical physicist of Nancy and Lille in collaboration with Equal-Estro Laboratory.
  
  
  METHODS
  A head and neck anthropomorphic phantom and a water-equivalent homogeneous cubic plastic test-object, so-called "MiniCube", have been used. Powder and solid thermoluminescent dosimeters as well as radiochromic films have been used to perform absolute and relative dose studies, respectively. The comparison between doses calculated by Multiplan treatment planning system and measured doses have been studied in absolute dose. The dose distributions measured with films and treatment planning system calculations have been compared via the gamma function, configured with different tolerance criteria.
  
  
  RESULTS
  This work allowed, via solid thermoluminescent dosimeter measurements, verifying the beam reliability with a reproducibility of 1.7 %. The absolute dose measured in the phantom irradiated by the seven participating centres has shown an error inferior to the standard tolerance limits (± 5 %), for most of participating centres. The relative dose measurements performed at Nancy and by the Equal-Estro laboratory allowed defining the most adequate parameters for gamma index (5 %/2mm--with at least 95 % of pixels satisfying acceptability criteria: γ<1). These parameters should be independent of the film analysis software.
  
  
  CONCLUSIONS
  This work allowed defining a dosimetric external quality control for CyberKnife(®) systems, based on a reproducible irradiation plan through measurements performed with thermoluminescent dosimeters and radiochromic films. This protocol should be validated by a new series of measurement and taking into account the lessons of this work.
authors.affiliation: Institut de Cancérologie de Lorraine, Avenue de Bourgogne, CS 30519, 54519 Vandœuvre-lès-Nancy, France. lucieguinement@hotmail.com
authors.forename: L
authors.initials: L
authors.lastname: Guinement
authors.forename: V
authors.initials: V
authors.lastname: Marchesi
authors.forename: A
authors.initials: A
authors.lastname: Veres
authors.forename: T
authors.initials: T
authors.lastname: Lacornerie
authors.forename: I
authors.initials: I
authors.lastname: Buchheit
authors.forename: D
authors.initials: D
authors.lastname: Peiffert
mesh_terms: D002138:Calibration; D003124:Colorimetry / Q000379:methods; D003299:Cooperative Behavior; D005459:Fluorides / Q000528:radiation effects; D006801:Humans; D018020:Lithium Compounds / Q000528:radiation effects; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D010865:Pilot Projects; D011208:Powders; D011785:Quality Assurance, Health Care / Q000458:organization & administration*; D011786:Quality Control; D011874:Radiometry / Q000379:methods / Q000592:standards*; D016634:Radiosurgery / Q000295:instrumentation / Q000592:standards*; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results; D012371:Robotics / Q000295:instrumentation; D012394:Rosaniline Dyes / Q000528:radiation effects; D013819:Thermoluminescent Dosimetry / Q000379:methods
chemical_list: D018020:Lithium Compounds; D011208:Powders; D012394:Rosaniline Dyes; C027651:lithium fluoride; D005459:Fluorides
keywords: Contrôle qualité externe; CyberKnife; DTL; Dosimètre thermoluminescent; External quality control; Films radiochromiques; Radiochromic film; TLD; Thermoluminescent dosimeter