title: Pretreatment quality assurance of flattening filter free beams on 224 patients for intensity modulated plans: a multicentric study.
abstract: OBJECTIVE
  Pretreatment quality assurance data from four centers, members of the European TrueBeam council were analyzed with different verification devices to assess reliability of flattening filter free beam delivery for intensity modulated radiotherapy (IMRT) and RapidArc (RA) techniques.
  
  
  METHODS
  TrueBeam(®) (Varian Medical System) is a new linear accelerator designed for delivering flattened, as well as flattening filter free beams. Pretreatment dosimetric validation of plan delivery was performed with different verification devices and responses to high dose rates were tested. Treatment planning was done in Eclipse planning system (PRO 8.9, AAA 8.9). γ evaluation was performed with (dose difference) = 3% and (distance to agreement) = 3 mm scoring the gamma agreement index (GAI, % of field area passing the test). Two hundred and twenty-four patients with 1-6 lesions in various anatomical regions and dose per fraction ranging from 1.8 Gy to 25 Gy were included in the study; 88 were treated with 6 MV flattening filter free (X6FFF) beam energy and 136 with 10 MV flattening filter free (X10FFF) beam. Gafchromic films in solid water, delta(4), arccheck, and matrixx phantom were used to verify the dose distributions. Additionally, point measurements were performed using a PinPoint chamber and a Farmer chamber.
  
  
  RESULTS
  Dose calculation as well as dose delivery was equally accurate for IMRT and RA delivery (IMRT: GAI = 99.3% (±1.1); RA: GAI = 98.8% (±1.1) as well as for the two beams evaluated (X6FFF: GAI = 99.1% (±1.0); X10FFF: GAI = 98.8% (±1.2). Only small differences were found for the four verification devices. A point dose verification was performed on 52 cases, obtaining a dose deviation of 0.34%. The GAI variations with number of monitor units were statistically significant.
  
  
  CONCLUSIONS
  The TrueBeam FFF modality, analyzed with a variety of verification devices and planned with Eclipse planning system is dosimetrically accurate (within the specified limits 3 mm/3%) for both X6FFF and X10FFF beam energy.
authors.affiliation: Department of Radiation Oncology, 8091 Zurich, Switzerland.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Lang
authors.forename: Giacomo
authors.initials: G
authors.lastname: Reggiori
authors.forename: Josep
authors.initials: J
authors.lastname: Puxeu Vaquee
authors.forename: Carlos
authors.initials: C
authors.lastname: Calle
authors.forename: Jan
authors.initials: J
authors.lastname: Hrbacek
authors.forename: Stephan
authors.initials: S
authors.lastname: Klock
authors.forename: Marta
authors.initials: M
authors.lastname: Scorsetti
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
authors.forename: Pietro
authors.initials: P
authors.lastname: Mancosu
mesh_terms: D006801:Humans; D011786:Quality Control; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000592:standards*; D015203:Reproducibility of Results