title: The rationale and technique of staged-volume arteriovenous malformation radiosurgery.
abstract: OBJECTIVE
  Stereotactic radiosurgery is an effective management strategy for properly selected arteriovenous malformation (AVM) patients. However, the risk of postradiosurgical radiation-related injury generally limits this procedure to patients with AVMs of an average diameter of 3 cm or less. Radiosurgery of large AVMs in a planned staged fashion was undertaken to limit the radiation exposure to the surrounding normal brain.
  
  
  METHODS
  Between April 1997 and December 1999, 10 patients with a median AVM volume of 17.4 cm(3) (range, 7.4-53.3 cm(3)) underwent staged-volume radiosurgery (23 procedures). At the first radiosurgical procedure, the total volume of the AVM is estimated and a dose plan calculated that covers 10 cm(3)-15 cm(3), or one-half the nidus volume if the AVM is critically located (brainstem, thalamus, or basal ganglia). At 6-month intervals thereafter, radiosurgery was repeated to different portions of the AVM with the previous dose plan(s) being re-created utilizing intracranial landmarks to minimize radiation overlap. Radiosurgical procedures were continued until the entire malformation has been irradiated.
  
  
  RESULTS
  The radiation dosimetry of staged-volume AVM radiosurgery was compared to hypothetical single-session procedures for the 10 patients. Staged-volume radiosurgery decreased the 12-Gy volume by an average of 11.1% (range, 4.9-21%) (p < 0.001). The non-AVM 12-Gy volume was reduced by an average of 27.2% (range, 12.5-51.3%) (p < 0.001).
  
  
  CONCLUSIONS
  Staged-volume radiosurgery of large AVMs results in less radiation exposure to the adjacent brain. Further follow-up is needed to determine whether this technique provides a high rate of AVM obliteration while maintaining an acceptable rate of radiation-related complications.
authors.affiliation: Department of Neurological Surgery, Mayo Clinic and Foundation, Rochester, MN 55905, USA. bruce.pollock@mayo.edu
authors.forename: B E
authors.initials: BE
authors.lastname: Pollock
authors.forename: R W
authors.initials: RW
authors.lastname: Kline
authors.forename: S L
authors.initials: SL
authors.lastname: Stafford
authors.forename: R L
authors.initials: RL
authors.lastname: Foote
authors.forename: P J
authors.initials: PJ
authors.lastname: Schomberg
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D016634:Radiosurgery / Q000379:methods*; D012086:Reoperation; D013997:Time Factors