title: Comparison of Elekta VMAT with helical tomotherapy and fixed field IMRT: plan quality, delivery efficiency and accuracy.
abstract: OBJECTIVE
  Helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) are arc-based approaches to IMRT delivery. The objective of this study is to compare VMAT to both HT and fixed field IMRT in terms of plan quality, delivery efficiency, and accuracy.
  
  
  METHODS
  Eighteen cases including six prostate, six head-and-neck, and six lung cases were selected for this study. IMRT plans were developed using direct machine parameter optimization in the Pinnacle3 treatment planning system. HT plans were developed using a Hi-Art II planning station. VMAT plans were generated using both the Pinnacle3 SmartArc IMRT module and a home-grown arc sequencing algorithm. VMAT and HT plans were delivered using Elekta's PreciseBeam VMAT linac control system (Elekta AB, Stockholm, Sweden) and a TomoTherapy Hi-Art II system (TomoTherapy Inc., Madison, WI), respectively. Treatment plan quality assurance (QA) for VMAT was performed using the IBA MatriXX system while an ion chamber and films were used for HT plan QA.
  
  
  RESULTS
  The results demonstrate that both VMAT and HT are capable of providing more uniform target doses and improved normal tissue sparing as compared with fixed field IMRT. In terms of delivery efficiency, VMAT plan deliveries on average took 2.2 min for prostate and lung cases and 4.6 min for head-and-neck cases. These values increased to 4.7 and 7.0 min for HT plans.
  
  
  CONCLUSIONS
  Both VMAT and HT plans can be delivered accurately based on their own QA standards. Overall, VMAT was able to provide approximately a 40% reduction in treatment time while maintaining comparable plan quality to that of HT.
authors.affiliation: Department of Radiation Oncology, Swedish Cancer Institute, 1221 Madison St., Seattle, Washington 98104, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Rao
authors.forename: Wensha
authors.initials: W
authors.lastname: Yang
authors.forename: Fan
authors.initials: F
authors.lastname: Chen
authors.forename: Ke
authors.initials: K
authors.lastname: Sheng
authors.forename: Jinsong
authors.initials: J
authors.lastname: Ye
authors.forename: Vivek
authors.initials: V
authors.lastname: Mehta
authors.forename: David
authors.initials: D
authors.lastname: Shepard
authors.forename: Daliang
authors.initials: D
authors.lastname: Cao
mesh_terms: D001822:Body Burden; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy*; D011786:Quality Control; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity