title: Comparing step-and-shoot IMRT with dynamic helical tomotherapy IMRT plans for head-and-neck cancer.
abstract: OBJECTIVE
  The goal of this planning study was to compare step-and-shoot intensity-modulated radiotherapy (IMRT) plans with helical dynamic IMRT plans for oropharynx patients on the basis of dose distribution.
  
  
  METHODS
  Five patients with oropharynx cancer had been previously treated by step-and-shoot IMRT at the University Medical Centre Utrecht, The Netherlands, applying five fields and approximately 60-90 segments. Inverse planning was carried out using Plato, version 2.6.2. For each patient, an inverse IMRT plan was also made using Tomotherapy Hi-Art System, version 2.0, and using the same targets and optimization goals. Statistical analysis was performed by a paired t test.
  
  
  RESULTS
  All tomotherapy plans compared favorably with the step-and-shoot plans regarding sparing of the organs at risk and keeping an equivalent target dose homogeneity. Tomotherapy plans in particular realized sharper dose gradients compared with the step-and-shoot plans. The mean dose to all parotid glands (n = 10) decreased on average 6.5 Gy (range, -4 to 14; p = 0.002). The theoretical reduction in normal tissue complication probabilities in favor of the tomotherapy plans depended on the parotid normal tissue complication probability model used (range, -3% to 32%).
  
  
  CONCLUSIONS
  Helical tomotherapy IMRT plans realized sharper dose gradients compared with the clinically applied step-and shoot plans. They are expected to be able to reduce the parotid normal tissue complication probability further, keeping a similar target dose homogeneity.
authors.affiliation: Department of Radiation Oncology, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors.forename: Marco
authors.initials: M
authors.lastname: van Vulpen
authors.forename: Colin
authors.initials: C
authors.lastname: Field
authors.forename: Cornelis P J
authors.initials: CP
authors.lastname: Raaijmakers
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Parliament
authors.forename: Chris H J
authors.initials: CH
authors.lastname: Terhaard
authors.forename: Marc A
authors.initials: MA
authors.lastname: MacKenzie
authors.forename: Rufus
authors.initials: R
authors.lastname: Scrimger
authors.forename: Jan J W
authors.initials: JJ
authors.lastname: Lagendijk
authors.forename: B Gino
authors.initials: BG
authors.lastname: Fallone
mesh_terms: D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D006801:Humans; D010306:Parotid Gland / Q000000981:diagnostic imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D036542:Tomography, Spiral Computed