title: Fast arc delivery for stereotactic body radiotherapy of vertebral and lung tumors.
abstract: OBJECTIVE
  Flattening filter-free (FFF) beams with higher dose rates and faster delivery are now clinically available. The purpose of this planning study was to compare optimized non-FFF and FFF RapidArc plans for stereotactic body radiotherapy (SBRT) and to validate the accuracy of fast arc delivery.
  
  
  METHODS
  Ten patients with peripheral lung tumors and 10 with vertebral metastases were planned using RapidArc with a flattened 6-MV photon beam and a 10-MV FFF beam for fraction doses of 7.5-18 Gy. Dosimetry of the target and organs at risk (OAR), number of monitor units (MU), and beam delivery times were assessed. GafChromic EBT2 film measurements of FFF plans were performed to compare calculated and delivered dose distributions.
  
  
  RESULTS
  No major dosimetric differences were seen between the two delivery techniques. For lung SBRT plans, conformity indices and OAR doses were similar, although the average MU required were higher with FFF plans. For vertebral SBRT, FFF plans provided comparable PTV coverage, with no significant differences in OAR doses. Average beam delivery times were reduced by a factor of up to 2.5, with all FFF fractions deliverable within 4 min. Measured FFF plans showed high agreement with calculated plans, with more than 99% of the area within the region of interest fulfilling the acceptance criterion.
  
  
  CONCLUSIONS
  The higher dose rate of FFF RapidArc reduces delivery times significantly, without compromising plan quality or accuracy of dose delivery.
authors.affiliation: Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands. c.ong@vumc.nl
authors.forename: Chin Loon
authors.initials: CL
authors.lastname: Ong
authors.forename: Wilko F A R
authors.initials: WF
authors.lastname: Verbakel
authors.forename: Max
authors.initials: M
authors.lastname: Dahele
authors.forename: Johan P
authors.initials: JP
authors.lastname: Cuijpers
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Slotman
authors.forename: Suresh
authors.initials: S
authors.lastname: Senan
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000601:surgery*; D019583:Dose Fractionation, Radiation; D004947:Esophagus / Q000000981:diagnostic imaging / Q000528:radiation effects; D005373:Film Dosimetry / Q000379:methods; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects*; D017785:Photons; D011859:Radiography; D016634:Radiosurgery / Q000379:methods* / Q000592:standards; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods* / Q000592:standards; D012189:Retrospective Studies; D013116:Spinal Cord / Q000000981:diagnostic imaging / Q000528:radiation effects; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary / Q000601:surgery*; D035441:Thoracic Wall / Q000000981:diagnostic imaging / Q000528:radiation effects; D013997:Time Factors; D014132:Trachea / Q000000981:diagnostic imaging / Q000528:radiation effects; D047368:Tumor Burden