title: Commissioning Monte Carlo algorithm for robotic radiosurgery using cylindrical 3D-array with variable density inserts.
abstract: BACKGROUND
  To commission the Monte Carlo (MC) algorithm based model of CyberKnife robotic stereotactic system (CK) and evaluate the feasibility of patient specific QA using the ArcCHECK cylindrical 3D-array (AC) with Multiplug inserts (MP).
  
  
  RESULTS
  Four configurations were used for simple beam setup and two for patient QA, replacing water equivalent inserts by lung. For twelve collimators (5-60mm) in simple setup, mean (SD) differences between MC and RayTracing algorithm (RT) of the number of points failing the 3%/1mmgamma criteria were 1(1), 1(3), 1(2) and 1(2) for the four MP configurations. Tracking fiducials were placed within AC for patient QA. Single lung insert setup resulted in mean gamma-index 2%/2mm of 90.5% (range [74.3-95.9]) and 82.3% ([66.8-94.5]) for MC and RT respectively, while 93.5% ([86.8-98.2]) and 86.2% ([68.7-95.4]) in presence of largest inhomogeneities, showing significant differences (p<0.05).
  
  
  CONCLUSIONS
  After evaluating the potential effects, 1.12g/cc PMMA and 0.09g/cc lung material assignment showed the best results. Overall, MC-based model showed superior results compared to RT for simple and patient specific testing, using a 2%/2mm criteria. Results are comparable with other reported commissionings for flattening filter free (FFF) delivery. Further improvement of MC calculation might be challenging as Multiplan has limited material library.
  
  
  CONCLUSIONS
  The AC with Multiplug allowed for comprehensive commissioning of CyberKnife MC algorithm and is useful for patient specific QA for stereotactic body radiation therapy. MC calculation accuracy might be limited due to Multiplan's insufficient material library; still results are comparable with other reported commissioning measurements using FFF beams.
authors.affiliation: Liege University Hospital, Liège, Belgium. Electronic address: ddechambre@chu.ulg.ac.be.
authors.forename: D
authors.initials: D
authors.lastname: Dechambre
authors.affiliation: Liege University Hospital, Liège, Belgium.
authors.forename: V
authors.initials: V
authors.lastname: Baart
authors.affiliation: Liege University Hospital, Liège, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Cucchiaro
authors.affiliation: Liege University Hospital, Liège, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Ernst
authors.affiliation: Liege University Hospital, Liège, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Jansen
authors.affiliation: Liege University Hospital, Liège, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Berkovic
authors.affiliation: Liege University Hospital, Liège, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Mievis
authors.affiliation: Liege University Hospital, Liège, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Coucke
authors.affiliation: Liege University Hospital, Liège, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Gulyban
mesh_terms: D000465:Algorithms; D005240:Feasibility Studies; D006801:Humans; D008168:Lung / Q000528:radiation effects; D009010:Monte Carlo Method; D010315:Particle Accelerators; D016634:Radiosurgery / Q000295:instrumentation*; D012371:Robotics
keywords: CyberKnife; Monte-Carlo commissioning; Pretreatment verification; SBRT