title: Quality assurance of a system for improved target localization and patient set-up that combines real-time infrared tracking and stereoscopic X-ray imaging.
abstract: OBJECTIVE
  The aim of this study is to investigate the positional accuracy of a prototype X-ray imaging tool in combination with a real-time infrared tracking device allowing automated patient set-up in three dimensions.
  
  
  METHODS
  A prototype X-ray imaging tool has been integrated with a commercially released real-time infrared tracking device. The system, consisting of two X-ray tubes mounted to the ceiling and a centrally located amorphous silicon detector has been developed for automated patient positioning from outside the treatment room prior to treatment. Two major functions are supported: (a) automated fusion of the actual treatment images with digitally reconstructed radiographs (DRRs) representing the desired position; (b) matching of implanted radio opaque markers. Measurements of known translational (up to 30.0mm) and rotational (up to 4.0 degrees ) set-up errors in three dimensions as well as hidden target tests have been performed on anthropomorphic phantoms.
  
  
  RESULTS
  The system's accuracy can be represented with the mean three-dimensional displacement vector, which yielded 0.6mm (with an overall SD of 0.9mm) for the fusion of DRRs and X-ray images. Average deviations between known translational errors and calculations varied from -0.3 to 0.6mm with a standard deviation in the range of 0.6-1.2mm. The marker matching algorithm yielded a three-dimensional uncertainty of 0.3mm (overall SD: 0.4mm), with averages ranging from 0.0 to 0.3mm and a standard deviation in the range between 0.3 and 0.4mm.
  
  
  CONCLUSIONS
  The stereoscopic X-ray imaging device integrated with the real-time infrared tracking device represents a positioning tool allowing for the geometrical accuracy that is required for conformal radiation therapy of abdominal and pelvic lesions, within an acceptable time-frame.
authors.affiliation: Department of Radiotherapy, Oncologic Center, Academic Hospital, Free University of Brussels, Laarbeeklaan 101, B-1090, Brussels, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Verellen
authors.forename: Guy
authors.initials: G
authors.lastname: Soete
authors.forename: Nadine
authors.initials: N
authors.lastname: Linthout
authors.forename: Swana
authors.initials: S
authors.lastname: Van Acker
authors.forename: Patsy
authors.initials: P
authors.lastname: De Roover
authors.forename: Vincent
authors.initials: V
authors.lastname: Vinh-Hung
authors.forename: Jan
authors.initials: J
authors.lastname: Van de Steene
authors.forename: Guy
authors.initials: G
authors.lastname: Storme
mesh_terms: D000465:Algorithms; D003196:Computer Graphics; D006801:Humans; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000295:instrumentation / Q000592:standards*