title: Evaluation of the optimal combinations of modulation factor and pitch for Helical TomoTherapy plans made with TomoEdge using Pareto optimal fronts.
abstract: BACKGROUND
  Modulation factor (MF) and pitch have an impact on Helical TomoTherapy (HT) plan quality and HT users mostly use vendor-recommended settings. This study analyses the effect of these two parameters on both plan quality and treatment time for plans made with TomoEdge planning software by using the concept of Pareto optimal fronts.
  
  
  METHODS
  More than 450 plans with different combinations of pitch [0.10-0.50] and MF [1.2-3.0] were produced. These HT plans, with a field width (FW) of 5 cm, were created for five head and neck patients and homogeneity index, conformity index, dose-near-maximum (D2), and dose-near-minimum (D98) were analysed for the planning target volumes, as well as the mean dose and D2 for most critical organs at risk. For every dose metric the median value will be plotted against treatment time. A Pareto-like method is used in the analysis which will show how pitch and MF influence both treatment time and plan quality.
  
  
  RESULTS
  For small pitches (≤0.20), MF does not influence treatment time. The contrary is true for larger pitches (≥0.25) as lowering MF will both decrease treatment time and plan quality until maximum gantry speed is reached. At this moment, treatment time is saturated and only plan quality will further decrease.
  
  
  CONCLUSIONS
  The Pareto front analysis showed optimal combinations of pitch [0.23-0.45] and MF > 2.0 for a FW of 5 cm. Outside this range, plans will become less optimal. As the vendor-recommended settings fall within this range, the use of these settings is validated.
authors.affiliation: Department of Radiotherapy, University Radiotherapy Antwerp (URA), Antwerp, Belgium. geert.dekerf@gza.be.|Present address: Department of Radiotherapy, Iridium Cancer Network, GZA Sint-Augustinus, Oosterveldlaan 24, 2610, Wilrijk, Antwerp, Belgium. geert.dekerf@gza.be.
authors.forename: Geert
authors.initials: G
authors.lastname: De Kerf
authors.affiliation: Department of Radiotherapy, University Radiotherapy Antwerp (URA), Antwerp, Belgium.|Present address: Department of Radiotherapy, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Van Gestel
authors.affiliation: Department of Radiotherapy, University Radiotherapy Antwerp (URA), Antwerp, Belgium.
authors.forename: Lobke
authors.initials: L
authors.lastname: Mommaerts
authors.affiliation: Department of Radiotherapy, University Radiotherapy Antwerp (URA), Antwerp, Belgium.
authors.forename: Danielle
authors.initials: D
authors.lastname: Van den Weyngaert
authors.affiliation: Radiotherapy UZ Brussel, Faculty of Medicine and Pharmacy Vrije Universiteit Brussel, Brussels, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Verellen
mesh_terms: D006801:Humans; D058958:Organs at Risk; D009959:Oropharyngeal Neoplasms / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012984:Software