title: C-arm-based three-dimensional navigation: a preliminary feasibility study.
abstract: OBJECTIVE
  With the new Siremobil Iso-C3D C-arm, three-dimensional (3D) datasets can be acquired intraoperatively in near-real time. Preliminary studies investigated the advantages of this system for depiction in joint and spinal surgery. Three-dimensional navigation seems feasible using the DICOM dataset of the Siremobil Iso-C3D in navigation devices. An experimental study was designed to investigate the feasibility and accuracy of this new technique.
  
  
  METHODS
  After implantation of fiducial markers (titanium mini-screws, Leibinger), a Siremobil Iso-C3D C-arm with standard imaging options was used to acquire pre-interventional 3D datasets of the specimens. These isotropic voxel data were transferred via DICOM to a medivision navigation system using the spine module. After registration of the fiducials, a total of 20 pedicle screws were implanted (in 4 artificial-bone vertebral bodies and 6 cadaver vertebrae in situ) with the use of the navigation system in real-time mode. Post-interventionally, Iso-C3D and CT scans were obtained to control for implant position in the cadaver study.
  
  
  RESULTS
  Fiducial marker implantation and registration require a special protocol to ensure correct identification and patient orientation in the DICOM dataset. The obtained accuracy was within 2 mm. Post-interventional imaging of the cadaveric vertebrae showed 10 of 12 screws to be correctly placed, with the other two in marginal intraosseous positions.
  
  
  CONCLUSIONS
  Three-dimensional navigation with the Siremobil Iso-C3D data set is feasible, the accuracy being comparable to that of CT-based navigation and adequate for clinical interventions. Fiducial marker-based registration allows navigation of different bones in the same dataset without additional 3D scanning. This method is very useful as an additional tool in registration-free Iso-C3D-based navigation, since the navigation system allows the use of only one dynamic reference base (DRB).
authors.affiliation: Surgical Clinic and Polyclinic, Klinikum of the University of Munich-Innenstadt, Munich, Germany. euler@ch-i.med.uni-muenchen.de
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Euler
authors.forename: Sandro
authors.initials: S
authors.lastname: Heining
authors.forename: Christian
authors.initials: C
authors.lastname: Riquarts
authors.forename: Wolf
authors.initials: W
authors.lastname: Mutschler
mesh_terms: D001863:Bone Screws; D005240:Feasibility Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D066298:In Vitro Techniques; D007432:Intraoperative Period; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000601:surgery*; D019047:Phantoms, Imaging; D025321:Surgery, Computer-Assisted