title: The first clinical implementation of electromagnetic transponder-guided MLC tracking.
abstract: OBJECTIVE
  We report on the clinical process, quality assurance, and geometric and dosimetric results of the first clinical implementation of electromagnetic transponder-guided MLC tracking which occurred on 28 November 2013 at the Northern Sydney Cancer Centre.
  
  
  METHODS
  An electromagnetic transponder-based positioning system (Calypso) was modified to send the target position output to in-house-developed MLC tracking code, which adjusts the leaf positions to optimally align the treatment beam with the real-time target position. Clinical process and quality assurance procedures were developed and performed. The first clinical implementation of electromagnetic transponder-guided MLC tracking was for a prostate cancer patient being treated with dual-arc VMAT (RapidArc). For the first fraction of the first patient treatment of electromagnetic transponder-guided MLC tracking we recorded the in-room time and transponder positions, and performed dose reconstruction to estimate the delivered dose and also the dose received had MLC tracking not been used.
  
  
  RESULTS
  The total in-room time was 21 min with 2 min of beam delivery. No additional time was needed for MLC tracking and there were no beam holds. The average prostate position from the initial setup was 1.2 mm, mostly an anterior shift. Dose reconstruction analysis of the delivered dose with MLC tracking showed similar isodose and target dose volume histograms to the planned treatment and a 4.6% increase in the fractional rectal V60. Dose reconstruction without motion compensation showed a 30% increase in the fractional rectal V60 from that planned, even for the small motion.
  
  
  CONCLUSIONS
  The real-time beam-target correction method, electromagnetic transponder-guided MLC tracking, has been translated to the clinic. This achievement represents a milestone in improving geometric and dosimetric accuracy, and by inference treatment outcomes, in cancer radiotherapy.
authors: Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia.
authors: Paul J
authors: PJ
authors: Keall
authors: Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia and Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW 2065, Australia.
authors: Emma
authors: E
authors: Colvill
authors: Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia.
authors: Ricky
authors: R
authors: O'Brien
authors: Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia.
authors: Jin Aun
authors: JA
authors: Ng
authors: Department of Oncology, Aarhus University Hospital, Aarhus 8000, Denmark and Institute of Clinical Medicine, Aarhus University, Aarhus 8000, Denmark.
authors: Per Rugaard
authors: PR
authors: Poulsen
authors: Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW 2065, Australia.
authors: Thomas
authors: T
authors: Eade
authors: Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW 2065, Australia.
authors: Andrew
authors: A
authors: Kneebone
authors: Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW 2065, Australia.
authors: Jeremy T
authors: JT
authors: Booth
mesh_terms: D000465:Algorithms; D055590:Electromagnetic Phenomena; D006801:Humans; D011786:Quality Control; D011874:Radiometry; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012984:Software