title: Analysis of fiducial markers used for on-line verification in the external-beam radiotherapy of patients with cranial tumours.
abstract: OBJECTIVE
  Evaluate the fiducial marker-based position verification in the external-beam radiotherapy of patients with cranial tumour.
  
  
  METHODS
  Thirteen patients with intracranial tumours were treated with external- beam radiotherapy using 3 gold markers implanted in the skull. Before each fraction the patient was positioned on the treatment table and 2 orthogonal portal images were performed to localise the 3 gold seeds and the target position was calculated using a commercialised computer program (ISOLOC software, MEDTEC). This program provides the couch movements required to move the target to the isocentre.
  
  
  RESULTS
  When the set-up error was corrected using the coordinates of the 3 markers, the final movements were less than 2 mm in all cases: lateral, mean v., 1.21 mm; longitudinal, 1.23 mm; and anteroposterior, 1.18 mm. No serious complications related to the gold marker insertion were noted.
  
  
  CONCLUSIONS
  The use of 3 implanted fiducial seeds is an optimal technique for precise set-up in patients with brain tumours treated with external radiotherapy. This commercial system is highly suitable for fractionated stereotactic irradiation.
authors.affiliation: Oncología Radioterápica, Plataforma de Oncología, USP Hospital San Jaime, Torrevieja, Alicante, Spain. rosam.canon@usphospitales.com
authors.forename: R Ma
authors.initials: RM
authors.lastname: Cañón
authors.forename: I
authors.initials: I
authors.lastname: Azinovic
authors.forename: M
authors.initials: M
authors.lastname: Lobato
authors.forename: J
authors.initials: J
authors.lastname: Navarro
authors.forename: J
authors.initials: J
authors.lastname: Rebollo
mesh_terms: D015415:Biomarkers / Q000032:analysis; D001932:Brain Neoplasms / Q000532:radiotherapy*; D006801:Humans; D019736:Prostheses and Implants; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012886:Skull / Q000000981:diagnostic imaging
chemical_list: D015415:Biomarkers