title: The optimal tomotherapy treatment planning parameters for extremity soft tissue sarcomas.
abstract: OBJECTIVE
  To determine the optimum combination of treatment parameters between pitch, field width (FW) and modulation factor (MF) for extremity sarcomas in tomotherapy.
  
  
  METHODS
  Six patients previously treated for extremity sarcomas (3 arms and 3 legs) with tomotherapy were included in this study. 288 treatment plans were recalculated, corresponding to all combinations between 2 FW (2.5 and 5 cm), 4 MF (1.5, 2, 2.5 and 3) and 6 pitches (0.215, 0.287, 0.43 and 3 off-axis pitches). The treatment parameters (MF, FW or pitch) are modified between each plan, and the calculation is relaunched for 400 iterations, without modifying the optimisation constraints of the plan under which the patient has been treated.
  
  
  RESULTS
  We suggest eliminating the 0.43 pitch and never combining a 0.215 pitch with an MF ≤ 2. We also do not recommend using an MF = 1.5 unless treatment time is an absolute priority over plan quality. We did not see any advantage in using Chen off-axis pitches, except for targets far from the axis (>15 cm) treated with a high pitch. A combination of MF = 2/FW = 5 cm/pitch = 0.287 gives plans of acceptable quality, combined with reduced treatment times. These conclusions are true only for extremity sarcomas treated in 2 Gy/fraction.
  
  
  CONCLUSIONS
  We have shown that the choice of pitch/MF/FW combination is crucial for the treatment of extremity sarcomas in tomotherapy: some produce good dosimetric quality with a reduced irradiation time, while others may increase the time without improving the quality.
authors.affiliation: Division of Medical Physics, Department of Radiotherapy, Paul Strauss Center, Strasbourg, France. Electronic address: pmeyer@strasbourg.unicancer.fr.
authors.forename: Philippe
authors.initials: P
authors.lastname: Meyer
authors.affiliation: Division of Medical Physics, Department of Radiotherapy, Paul Strauss Center, Strasbourg, France.
authors.forename: Hugo
authors.initials: H
authors.lastname: Bouhours
authors.affiliation: Division of Medical Physics, Department of Radiotherapy, Paul Strauss Center, Strasbourg, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Dehaynin
authors.affiliation: Division of Medical Physics, Department of Radiotherapy, Paul Strauss Center, Strasbourg, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Jarnet
authors.affiliation: Division of Medical Physics, Department of Radiotherapy, Paul Strauss Center, Strasbourg, France.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Gantier
authors.affiliation: Division of Medical Physics, Department of Radiotherapy, Paul Strauss Center, Strasbourg, France.
authors.forename: Diran
authors.initials: D
authors.lastname: Karamanoukian
authors.affiliation: Division of Medical Physics, Department of Radiotherapy, Paul Strauss Center, Strasbourg, France.
authors.forename: Claudine
authors.initials: C
authors.lastname: Niederst
mesh_terms: D000368:Aged; D001132:Arm; D005260:Female; D006801:Humans; D007866:Leg; D008297:Male; D008875:Middle Aged; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted; D012509:Sarcoma / Q000532:radiotherapy*
keywords: Field width; Modulation factor; Pitch; Sarcomas; Tomotherapy planning