title: Positioning accuracy of cone-beam computed tomography in combination with a HexaPOD robot treatment table.
abstract: OBJECTIVE
  To scrutinize the positioning accuracy and reproducibility of a commercial hexapod robot treatment table (HRTT) in combination with a commercial cone-beam computed tomography system for image-guided radiotherapy (IGRT).
  
  
  METHODS
  The mechanical stability of the X-ray volume imaging (XVI) system was tested in terms of reproducibility and with a focus on the moveable parts, i.e., the influence of kV panel and the source arm on the reproducibility and accuracy of both bone and gray value registration using a head-and-neck phantom. In consecutive measurements the accuracy of the HRTT for translational, rotational, and a combination of translational and rotational corrections was investigated. The operational range of the HRTT was also determined and analyzed.
  
  
  RESULTS
  The system performance of the XVI system alone was very stable with mean translational and rotational errors of below 0.2 mm and below 0.2 degrees , respectively. The mean positioning accuracy of the HRTT in combination with the XVI system summarized over all measurements was below 0.3 mm and below 0.3 degrees for translational and rotational corrections, respectively. The gray value match was more accurate than the bone match.
  
  
  CONCLUSIONS
  The XVI image acquisition and registration procedure were highly reproducible. Both translational and rotational positioning errors can be corrected very precisely with the HRTT. The HRTT is therefore well suited to complement cone-beam computed tomography to take full advantage of position correction in six degrees of freedom for IGRT. The combination of XVI and the HRTT has the potential to improve the accuracy of high-precision treatments.
authors.affiliation: Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand. juergen.meyer@canterbury.ac.nz
authors.forename: Jürgen
authors.initials: J
authors.lastname: Meyer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Wilbert
authors.forename: Kurt
authors.initials: K
authors.lastname: Baier
authors.forename: Matthias
authors.initials: M
authors.lastname: Guckenberger
authors.forename: Anne
authors.initials: A
authors.lastname: Richter
authors.forename: Otto
authors.initials: O
authors.lastname: Sauer
authors.forename: Michael
authors.initials: M
authors.lastname: Flentje
mesh_terms: D006257:Head; D019047:Phantoms, Imaging; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012371:Robotics / Q000295:instrumentation*; D012399:Rotation; D013679:Technology, Radiologic / Q000379:methods