title: Clinical use of a non-isocentric C-arm unit for on-line filmless reconstruction of brachytherapy applicators.
abstract: OBJECTIVE
  In this paper it is described how a mobile non-isocentric C-arm can be used to reconstruct brachytherapy applicators using an 'isocentric' imaging set-up without using an orthogonal reconstruction box.
  
  
  METHODS
  The images are on-line digitally transferred to the treatment planning system. In order to determine the physical dimensions of the C-arm a simple method is presented that makes use of the relation between the magnification factor and the translational degrees of freedom of the C-arm. A phantom has been used to determine the overall reconstruction accuracy.
  
  
  RESULTS
  The accuracy in the reconstruction of the distance between two points is better than 2 mm when using radiographs. If digital images are used the maximum error in reconstructed distances equals 3.6 mm for points located in the corners of the field of view, whereas in the central part of the field the errors are less than 2 mm.
authors.affiliation: Department of Radiation Oncology/Clinical Physics and Informatics, Vrije Universiteit Medical Centre, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands.
authors.forename: J P
authors.initials: JP
authors.lastname: Cuijpers
mesh_terms: D001918:Brachytherapy; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D011880:Radiotherapy Planning, Computer-Assisted