title: Comparable cell survival between high dose rate flattening filter free and conventional dose rate irradiation.
abstract: OBJECTIVE
  Investigation of clonogenic cell survival and cell proliferation following single dose and fractionated delivery of high dose rate flattening filter free (FFF) irradiation compared to conventional dose rates.
  
  
  METHODS
  The human astrocytoma D384, glioma T98 and lung carcinoma SW1573 cell lines were irradiated using either a single dose (0-12 Gy) or a fractionated protocol of 5 daily fractions of 2 Gy (D384) or 3 Gy (SW1573). Cells were irradiated inside a phantom using fixed gantry beams of a linear accelerator. A sliding window technique created homogeneous dose distributions over the surface of the cell cultures. Irradiations using standard beams (6 MV, 600 MU/min.) and high dose rate FFF beams (10 MV, 2400 MU/min.) were compared. Cell survival was determined by clonogenic assay. In the fractionated irradiation set-up, the number of clonogenic cells was estimated by including tumor cell proliferation during the overall treatment time in the analysis.
  
  
  RESULTS
  All cell lines showed equal cell survival following irradiation using either the FFF beams or conventional flattened (FF) beams. This was observed after single dose exposure (0-12 Gy) as well as after fractionated irradiation (p = 0.08 for D384 and 0.20 for SW1373 cell lines).
  
  
  CONCLUSIONS
  FFF irradiation with a dose rate of 2400 MU/min and four times higher dose per pulse compared to irradiation with FF beams did not change cell survival for three human cancer cell lines up to a fraction dose of 12 Gy compared to irradiation using FF beams.
authors.affiliation: Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Wilko F A R
authors.initials: WF
authors.lastname: Verbakel
authors.forename: Jaap
authors.initials: J
authors.lastname: van den Berg
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Slotman
authors.forename: Peter
authors.initials: P
authors.lastname: Sminia
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005374:Filtration / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008954:Models, Biological; D009369:Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed; D014410:Tumor Stem Cell Assay