title: A multicenter retrospective study of frameless robotic radiosurgery for intracranial arteriovenous malformation.
abstract: BACKGROUND
  CT-guided, frameless radiosurgery is an alternative treatment to traditional catheter-angiography targeted, frame-based methods for intracranial arteriovenous malformations (AVMs). Despite the widespread use of frameless radiosurgery for treating intracranial tumors, its use for treating AVM is not-well described.
  
  
  METHODS
  Patients who completed a course of single fraction radiosurgery at The University of North Carolina or Georgetown University between 4/1/2005-4/1/2011 with single fraction radiosurgery and received at least one follow-up imaging study were included. All patients received pre-treatment planning with CTA ± MRA and were treated on the CyberKnife (Accuray) radiosurgery system. Patients were evaluated for changes in clinical symptoms and radiographic changes evaluated with MRI/MRA and catheter-angiography.
  
  
  RESULTS
  Twenty-six patients, 15 male and 11 female, were included in the present study at a median age of 41 years old. The Spetzler-Martin grades of the AVMs included seven Grade I, 12 Grade II, six Grade III, and one Grade IV with 14 (54%) of the patients having a pre-treatment hemorrhage. Median AVM nidal volume was 1.62 cm(3) (0.57-8.26 cm(3)) and was treated with a median dose of 1900 cGy to the 80% isodose line. At median follow-up of 25 months, 15 patients had a complete closure of their AVM, 6 patients had a partial closure, and 5 patients were stable. Time since treatment was a significant predictor of response, with patients experience complete closure having on average 11 months more follow-up than patients with partial or no closure (p = 0.03). One patient experienced a post-treatment hemorrhage at 22 months.
  
  
  CONCLUSIONS
  Frameless radiosurgery can be targeted with non-invasive MRI/MRA and CTA imaging. Despite the difficulty of treating AVM without catheter angiography, early results with frameless, CT-guided radiosurgery suggest that it can achieve similar results to frame-based methods at these time points.
authors.affiliation: Department of Neurological Surgery, Icahn School of Medicine at Mount Sinai , New York, NY , USA.
authors.forename: Eric K
authors.initials: EK
authors.lastname: Oermann
authors.affiliation: Department of Neurological Surgery, Georgetown University School of Medicine , Washington, DC , USA.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Murthy
authors.affiliation: Department of Radiation Medicine, Georgetown University School of Medicine , Washington, DC , USA.
authors.forename: Viola
authors.initials: V
authors.lastname: Chen
authors.affiliation: Department of Neurological Surgery, Icahn School of Medicine at Mount Sinai , New York, NY , USA.
authors.forename: Advaith
authors.initials: A
authors.lastname: Baimeedi
authors.affiliation: Department of Neurological Surgery, The University of North Carolina at Chapel Hill , Chapel Hill, NC , USA.
authors.forename: Deanna
authors.initials: D
authors.lastname: Sasaki-Adams
authors.affiliation: Department of Neurological Surgery, Georgetown University School of Medicine , Washington, DC , USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: McGrail
authors.affiliation: Department of Radiation Medicine, Georgetown University School of Medicine , Washington, DC , USA.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Collins
authors.affiliation: Department of Neurological Surgery, The University of North Carolina at Chapel Hill , Chapel Hill, NC , USA.
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Ewend
authors.affiliation: Department of Radiation Medicine, Georgetown University School of Medicine , Washington, DC , USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Collins
keywords: CT angiography; arteriovenous malformations; image guided radiation therapy; outcomes; stereotactic radiosurgery