title: CT-MR image data fusion for computer-assisted navigated surgery of orbital tumors.
abstract: OBJECTIVE
  To demonstrate the value of multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) in the preoperative assessment of orbital tumors, and to present, particularly, CT and MR image data fusion for surgical planning and performance in computer-assisted navigated surgery of orbital tumors.
  
  
  METHODS
  In this retrospective case series, 10 patients with orbital tumors and associated complaints underwent MDCT and MRI of the orbit. MDCT was performed at high resolution, with a bone window level setting in the axial plane. MRI was performed with an axial 3D T1-weighted (w) gradient-echo (GE) contrast-enhanced sequence, in addition to a standard MRI protocol. First, MDCT and MR images were used to diagnose tumorous lesions compared to histology as a standard of reference. Then, the image data sets from CT and 3D T1-w GE sequences were merged on a workstation to create CT-MR fusion images that were used for interventional planning and intraoperative image guidance. The intraoperative accuracy of the navigation unit was measured, defined as the deviation between the same landmark in the navigation image and the patient. Furthermore, the clinical preoperative status was compared to the patients' postoperative outcome.
  
  
  RESULTS
  Radiological and histological diagnosis, which revealed 7 benign and 3 malignant tumors, were concordant in 7 of 10 cases (70%). The CT-MR fusion images supported the surgeon in the preoperative planning and improved the surgical performance. The mean intraoperative accuracy of the navigation unit was 1.35mm. Postoperatively, orbital complaints showed complete regression in 6 cases, were ameliorated notably in 3 cases, and remained unchanged in 1 case.
  
  
  CONCLUSIONS
  CT and MRI are essential for the preoperative assessment of orbital tumors. CT-MR image data fusion is an accurate tool for planning the correct surgical procedure, and can improve surgical results in computer-assisted navigated surgery of orbital tumors.
authors.affiliation: Department of Radiology/Division of Neuroradiology and Musculoskeletal Radiology, Medical University Vienna, Waehringerguertel 18-20, A-1090 Vienna, Austria. stefan.nemec@meduniwien.ac.at
authors.forename: Stefan Franz
authors.initials: SF
authors.lastname: Nemec
authors.forename: Philipp
authors.initials: P
authors.lastname: Peloschek
authors.forename: Maria Theresa
authors.initials: MT
authors.lastname: Schmook
authors.forename: Christian Robert
authors.initials: CR
authors.lastname: Krestan
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hauff
authors.forename: Christian
authors.initials: C
authors.lastname: Matula
authors.forename: Christian
authors.initials: C
authors.lastname: Czerny
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009918:Orbital Neoplasms / Q000175:diagnosis* / Q000601:surgery*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome