title: Standardization of terminology in stereotactic radiosurgery: Report from the Standardization Committee of the International Leksell Gamma Knife Society: special topic.
abstract: OBJECTIVE
  This report has been prepared to ensure more uniform reporting of Gamma Knife radiosurgery treatment parameters by identifying areas of controversy, confusion, or imprecision in terminology and recommending standards.
  
  
  METHODS
  Several working group discussions supplemented by clarification via email allowed the elaboration of a series of provisional recommendations. These were also discussed in open session at the 16th International Leksell Gamma Knife Society Meeting in Sydney, Australia, in March 2012 and approved subject to certain revisions and the performance of an Internet vote for approval from the whole Society. This ballot was undertaken in September 2012.
  
  
  RESULTS
  The recommendations in relation to volumes are that Gross Target Volume (GTV) should replace Target Volume (TV); Prescription Isodose Volume (PIV) should generally be used; the term Treated Target Volume (TTV) should replace TVPIV, GTV in PIV, and so forth; and the Volume of Accepted Tolerance Dose (VATD) should be used in place of irradiated volume. For dose prescription and measurement, the prescription dose should be supplemented by the Absorbed Dose, or DV% (for example, D95%), the maximum and minimum dose should be related to a specific tissue volume (for example, D2% or preferably D1 mm3), and the median dose (D50%) should be recorded routinely. The Integral Dose becomes the Total Absorbed Energy (TAE). In the assessment of planning quality, the use of the Target Coverage Ratio (TTV/ GTV), Paddick Conformity Index (PCI = TTV2/[GTV · PIV]), New Conformity Index (NCI = [GTV · PIV]/TTV2), Selectivity Index (TTV/PIV), Homogeneity Index (HI = [D2% –D98%]/D50%), and Gradient Index (GI = PIV0.5/PIV) are reemphasized. In relation to the dose to Organs at Risk (OARs), the emphasis is on dose volume recording of the VATD or the dose/volume limit (for example, V10) in most cases, with the additional use of a Maximum Dose to a small volume (such as 1 mm3) and/or a Point Dose and Mean Point Dose in certain circumstances, particularly when referring to serial organs. The recommendations were accepted by the International Leksell Gamma Knife Society by a vote of 92% to 8%.
  
  
  CONCLUSIONS
  An agreed-upon and uniform terminology and subsequent standardization of certain methods and procedures will advance the clinical science of stereotactic radiosurgery.
authors.affiliation: Department of Neurosurgery, Hygeia Hospital, Athens, Greece. m.torrens@hygeia.gr
authors.forename: Michael
authors.initials: M
authors.lastname: Torrens
authors.forename: Caroline
authors.initials: C
authors.lastname: Chung
authors.forename: Hyun-Tai
authors.initials: HT
authors.lastname: Chung
authors.forename: Patrick
authors.initials: P
authors.lastname: Hanssens
authors.forename: David
authors.initials: D
authors.lastname: Jaffray
authors.forename: Andras
authors.initials: A
authors.lastname: Kemeny
authors.forename: David
authors.initials: D
authors.lastname: Larson
authors.forename: Marc
authors.initials: M
authors.lastname: Levivier
authors.forename: Christer
authors.initials: C
authors.lastname: Lindquist
authors.forename: Bodo
authors.initials: B
authors.lastname: Lippitz
authors.forename: Josef
authors.initials: J
authors.lastname: Novotny
authors.forename: Ian
authors.initials: I
authors.lastname: Paddick
authors.forename: Dheerendra
authors.initials: D
authors.lastname: Prasad
authors.forename: Chung Ping
authors.initials: CP
authors.lastname: Yu
mesh_terms: D001932:Brain Neoplasms / Q000473:pathology* / Q000601:surgery*; D006801:Humans; D009493:Neurosurgery / Q000592:standards*; D016634:Radiosurgery / Q000592:standards*; D012955:Societies, Medical; D009626:Terminology as Topic