title: Quality assurance in intracoronary brachytherapy. Recommendations for determining the planning target length to avoid geographic miss.
abstract: OBJECTIVE
  A new method of assessing geographic miss (GM) in endovascular brachytherapy (EVBT) is applied to evaluate the quality of intracoronary brachytherapy treatments, retrospectively. Based on the Vienna experience, recommendations for adequate safety margins are derived to avoid GM.
  
  
  METHODS
  Evaluation is done on 136 vessels of 128 consecutive patients treated between October 1999 and July 2001. The quality of EVBT is assessed using the concept and terminology of the EVA GEC ESTRO task group. Evaluation of GM and/or safety margin is performed by comparing the outermost interventions with the reference isodose length (RIL) of the applied delivering devices on recorded compact disk (CD) angiograms. The RIL is defined as the length of the vessel segment, which receives at least 90% of the reference dose at the reference depth (=1 mm within the vessel). GM is defined as injured vessel segments, which receive a dose lower than 90% of reference dose. Measurements of intervention length (IL) and active source length (ASL) are performed with respect to anatomical landmarks within the vessel in the region of interest (e.g. stent edges), and by using the nominal length of the devices (balloons, sources) as a reference scale. The edges of RIL are determined by subtracting the length of the dose-fall-off zone (specific to the applied delivery devices: (192)Ir 4.5 mm, (90)Sr 2.5 mm, (32)P 2.0 mm) from the edges of ASL.
  
  
  RESULTS
  The described method to assess GM is applicable to 128 vessels (94%). GM is found in 23% of proximal edges and 20% of distal edges. 95% of all GM are observed if the total margin (proximal+distal margin) between RIL and IL is shorter than 10.5 mm.
  
  
  CONCLUSIONS
  GM in intracoronary brachytherapy can be widely avoided by adding an appropriate safety margin to the IL (5-6 mm each edge in this study) in order to determine the necessary RIL for a treatment.
authors.affiliation: Department of Radiotherapy and Radiobiology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria.
authors.forename: Rainer
authors.initials: R
authors.lastname: Schmid
authors.forename: Christian
authors.initials: C
authors.lastname: Kirisits
authors.forename: Bonni
authors.initials: B
authors.lastname: Syeda
authors.forename: Paul
authors.initials: P
authors.lastname: Wexberg
authors.forename: Peter
authors.initials: P
authors.lastname: Siostrzonek
authors.forename: Boris
authors.initials: B
authors.lastname: Pokrajac
authors.forename: Dietmar
authors.initials: D
authors.lastname: Georg
authors.forename: Dietmar
authors.initials: D
authors.lastname: Glogar
authors.forename: Richard
authors.initials: R
authors.lastname: Poetter
mesh_terms: D001918:Brachytherapy / Q000379:methods / Q000592:standards*; D023921:Coronary Stenosis / Q000532:radiotherapy*; D006801:Humans; D011785:Quality Assurance, Health Care; D011829:Radiation Dosage; D012189:Retrospective Studies; D016896:Treatment Outcome