title: A quantitative analysis of adverse radiation effects following Gamma Knife radiosurgery for arteriovenous malformations.
abstract: OBJECTIVE
  The authors review outcomes following Gamma Knife radiosurgery (GKRS) of cerebral arteriovenous malformations (AVMs) and their correlation to postradiosurgery adverse radiation effects (AREs).
  
  
  METHODS
  From a prospective institutional review board-approved database, the authors identified patients with a minimum of 2 years of follow-up and thin-slice T2-weighted MRI sequences for volumetric analysis. A total of 105 AVM patients were included. The authors analyzed the incidence and quantitative changes in AREs as a function of time after GKRS. Statistical analysis was performed to identify factors related to ARE development and changes in the ARE index.
  
  
  RESULTS
  The median clinical follow-up was 53.8 months (range 24-212.4 months), and the median MRI follow-up was 36.8 months (range 24-212.4 months). 47.6% of patients had an AVM with a Spetzler-Martin grade ≥ III. The median administered margin and maximum doses were 22 and 40 Gy, respectively. The overall obliteration rate was 70.5%. Of patients who showed complete obliteration, 74.4% developed AREs within 4-6 months after GKRS. Late-onset AREs (i.e., > 12 months) correlated to a failure to obliterate the nidus. 58.1% of patients who developed appreciable AREs (defined as ARE index > 8) proceeded to have a complete nidus obliteration. Appreciable AREs were found to be influenced by AVM nidus volume > 3 ml, lobar location, number of draining veins and feeding arteries, prior embolization, and higher margin dose. On the other hand, a minimum ARE index > 8 predicted obliteration (p = 0.043).
  
  
  CONCLUSIONS
  ARE development after radiosurgery follows a temporal pattern peaking at 7-12 months after stereotactic radiosurgery. The ARE index serves as an important adjunct tool in patient follow-up and outcome prediction.
authors.affiliation: Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia;
authors.forename: Or
authors.initials: O
authors.lastname: Cohen-Inbar
authors.affiliation: Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia;|Neurological Institute, Taipei Veteran General Hospital; and.|National Yang-Ming University, Taipei, Taiwan.
authors.forename: Cheng-Chia
authors.initials: CC
authors.lastname: Lee
authors.affiliation: Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia;
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia;
authors.forename: David
authors.initials: D
authors.lastname: Schlesinger
authors.affiliation: Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia;
authors.forename: Jason P
authors.initials: JP
authors.lastname: Sheehan
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology / Q000209:etiology; D011446:Prospective Studies; D016634:Radiosurgery / Q000009:adverse effects*; D055815:Young Adult
keywords: ARE = adverse radiation effect; AVM = arteriovenous malformation; GKRS = Gamma Knife radiosurgery; Gamma Knife; SRS = stereotactic radiosurgery; T2 changes; VRAS = Virginia Radiosurgery AVM Scale; arteriovenous malformation; complication; outcome; radiosurgery; stereotactic radiosurgery