title: Feasibility of a unified approach to intensity-modulated radiation therapy and volume-modulated arc therapy optimization and delivery.
abstract: OBJECTIVE
  To study the feasibility of unified intensity-modulated arc therapy (UIMAT) which combines intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) optimization and delivery to produce superior radiation treatment plans, both in terms of dose distribution and efficiency of beam delivery when compared with either VMAT or IMRT alone.
  
  
  METHODS
  An inverse planning algorithm for UIMAT was prototyped within the pinnacle treatment planning system (Philips Healthcare). The IMRT and VMAT deliveries are unified within the same arc, with IMRT being delivered at specific gantry angles within the arc. Optimized gantry angles for the IMRT and VMAT phases are assigned automatically by the inverse optimization algorithm. Optimization of the IMRT and VMAT phases is done simultaneously using a direct aperture optimization algorithm. Five treatment plans each for prostate, head and neck, and lung were generated using a unified optimization technique and compared with clinical IMRT or VMAT plans. Delivery verification was performed with an ArcCheck phantom (Sun Nuclear) on a Varian TrueBeam linear accelerator (Varian Medical Systems).
  
  
  RESULTS
  In this prototype implementation, the UIMAT plans offered the same target dose coverage while reducing mean doses to organs at risk by 8.4% for head-and-neck cases, 5.7% for lung cases, and 3.5% for prostate cases, compared with the VMAT or IMRT plans. In addition, UIMAT can be delivered with similar efficiency as VMAT.
  
  
  CONCLUSIONS
  In this proof-of-concept work, a novel radiation therapy optimization and delivery technique that interlaces VMAT or IMRT delivery within the same arc has been demonstrated. Initial results show that unified VMAT/IMRT has the potential to be superior to either standard IMRT or VMAT.
authors: Department of Physics and Engineering, London Regional Cancer Program, London, Ontario N6A 4L6, Canada; Department of Oncology, Western University, London, Ontario N6A 3K7, Canada; and Department of Medical Biophysics, Western University, London, Ontario N6A 3K7, Canada.
authors: Douglas A
authors: DA
authors: Hoover
authors: Department of Physics and Engineering, London Regional Cancer Program, London, Ontario N6A 4L6, Canada and Department of Medical Biophysics, Western University, London, Ontario N6A 3K7, Canada.
authors: Michael
authors: M
authors: MacFarlane
authors: Department of Oncology, Western University, London, Ontario N6A 3K7, Canada; Department of Medical Biophysics, Western University, London, Ontario N6A 3K7, Canada; and Department of Physics and Astronomy, Western University, London, Ontario N6A 3K7, Canada.
authors: Eugene
authors: E
authors: Wong
authors: Department of Physics and Engineering, London Regional Cancer Program, London, Ontario N6A 4L6, Canada; Department of Oncology, Western University, London, Ontario N6A 3K7, Canada; Department of Medical Biophysics, Western University, London, Ontario N6A 3K7, Canada; and Department of Physics and Astronomy, Western University, London, Ontario N6A 3K7, Canada.
authors: Jerry J
authors: JJ
authors: Battista
authors: Department of Physics and Engineering, London Regional Cancer Program, London, Ontario N6A 4L6, Canada; Department of Oncology, Western University, London, Ontario N6A 3K7, Canada; and Department of Medical Biophysics, Western University, London, Ontario N6A 3K7, Canada.
authors: Jeff Z
authors: JZ
authors: Chen
mesh_terms: D005240:Feasibility Studies; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*