title: Multileaf Collimator Tracking Improves Dose Delivery for Prostate Cancer Radiation Therapy: Results of the First Clinical Trial.
abstract: OBJECTIVE
  To test the hypothesis that multileaf collimator (MLC) tracking improves the consistency between the planned and delivered dose compared with the dose without MLC tracking, in the setting of a prostate cancer volumetric modulated arc therapy trial.
  
  
  METHODS
  Multileaf collimator tracking was implemented for 15 patients in a prostate cancer radiation therapy trial; in total, 513 treatment fractions were delivered. During each treatment fraction, the prostate trajectory and treatment MLC positions were collected. These data were used as input for dose reconstruction (multiple isocenter shift method) to calculate the treated dose (with MLC tracking) and the dose that would have been delivered had MLC tracking not been applied (without MLC tracking). The percentage difference from planned for target and normal tissue dose-volume points were calculated. The hypothesis was tested for each dose-volume value via analysis of variance using the F test.
  
  
  RESULTS
  Of the 513 fractions delivered, 475 (93%) were suitable for analysis. The mean difference and standard deviation between the planned and treated MLC tracking doses and the planned and without-MLC tracking doses for all 475 fractions were, respectively, PTV D99% -0.8% ± 1.1% versus -2.1% ± 2.7%; CTV D99% -0.6% ± 0.8% versus -0.6% ± 1.1%; rectum V65% 1.6% ± 7.9% versus -1.2% ± 18%; and bladder V65% 0.5% ± 4.4% versus -0.0% ± 9.2% (P<.001 for all dose-volume results).
  
  
  CONCLUSIONS
  This study shows that MLC tracking improves the consistency between the planned and delivered doses compared with the modeled doses without MLC tracking. The implications of this finding are potentially improved patient outcomes, as well as more reliable dose-volume data for radiobiological parameter determination.
authors.affiliation: Radiation Physics Laboratory, University of Sydney, Sydney, NSW, Australia; Northern Sydney Cancer Centre, Royal North Shore Hospital, St. Leonards, NSW, Australia.
authors.forename: Emma
authors.initials: E
authors.lastname: Colvill
authors.affiliation: Northern Sydney Cancer Centre, Royal North Shore Hospital, St. Leonards, NSW, Australia; School of Physics, University of Sydney, Sydney, NSW, Australia.
authors.forename: Jeremy T
authors.initials: JT
authors.lastname: Booth
authors.affiliation: Radiation Physics Laboratory, University of Sydney, Sydney, NSW, Australia.
authors.forename: Ricky T
authors.initials: RT
authors.lastname: O'Brien
authors.affiliation: Northern Sydney Cancer Centre, Royal North Shore Hospital, St. Leonards, NSW, Australia.
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Eade
authors.affiliation: Northern Sydney Cancer Centre, Royal North Shore Hospital, St. Leonards, NSW, Australia.
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Kneebone
authors.affiliation: Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Per R
authors.initials: PR
authors.lastname: Poulsen
authors.affiliation: Radiation Physics Laboratory, University of Sydney, Sydney, NSW, Australia. Electronic address: paul.keall@sydney.edu.au.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Keall
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D054893:Cone-Beam Computed Tomography; D019583:Dose Fractionation, Radiation; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D058958:Organs at Risk / Q000528:radiation effects; D010315:Particle Accelerators / Q000295:instrumentation; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects