title: Multi-staged robotic stereotactic radiosurgery for large cerebral arteriovenous malformations.
abstract: OBJECTIVE
  To investigate a multi-staged robotic stereotactic radiosurgery (SRS) delivery technique for the treatment of large cerebral arteriovenous malformations (AVMs). The treatment planning process and strategies to optimize both individual and composite dosimetry are discussed.
  
  
  METHODS
  Eleven patients with large (30.7 ± 19.2 cm(3)) AVMs were selected for this study. A fiducial system was designed for fusion of targets between planar angiograms and simulation CT scans. AVMs were contoured based on single contrast CT, MRI and orthogonal angiogram images. AVMs were divided into 3-8 sub-target volumes (3-7 cm(3)) for sequential treatment at 1-4 week intervals to a prescription dose of 16-20 Gy. Forward and inversely developed treatment plans were optimized for 95% coverage of the total AVM volume by dose summation from each sub-volume, while minimizing dose to surrounding tissues. Dose-volume analysis was used to evaluate the PTV coverage, dose conformality (CI), and R50 and V12 Gy parameters.
  
  
  RESULTS
  The treatment workflow was commissioned and able to localize within 1mm. Inverse optimization outperformed forward planning for most patients for each index considered. Dose conformality was shown comparable to staged Gamma Knife treatments.
  
  
  CONCLUSIONS
  The CyberKnife system is shown to be a practical delivery platform for multi-staged treatments of large AVMs using forward or inverse planning techniques.
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, USA. Electronic address: chuxiong.ding@utsouthwestern.edu.
authors.forename: Chuxiong
authors.initials: C
authors.lastname: Ding
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Solberg
authors.forename: Brian
authors.initials: B
authors.lastname: Hrycushko
authors.forename: Paul
authors.initials: P
authors.lastname: Medin
authors.forename: Louis
authors.initials: L
authors.lastname: Whitworth
authors.forename: Robert D
authors.initials: RD
authors.lastname: Timmerman
mesh_terms: D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D002538:Intracranial Arteriovenous Malformations / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012371:Robotics / Q000295:instrumentation / Q000379:methods*
keywords: Arteriovenous malformations; CyberKnife; Stereotactic radiosurgery