title: Accuracy of ultrasound to MR registration of the knee.
abstract: BACKGROUND
  Ultrasound-based registration to 3D surfaces segmented from MR imaging is proposed as a non-invasive alternative to point-based registration for image-guided surgery. By relying upon diagnostic MR imaging, the expense of additional CT imaging (and exposure to radiation) is avoided. The technique would enable navigation in arthroscopic and other minimally invasive procedures.
  
  
  METHODS
  Optically tracked registrations using point-based and ultrasound-based methods to MR and CT imaging volumes for two cadaveric specimens were acquired and analysed.
  
  
  RESULTS
  The average RMS distance between fiducials was 0.27 mm for CT and 0.72 mm for MR utilizing point-based registration. The average RMS distance for ultrasound-based registration to CT was 0.59 mm and 0.76 mm to MR. The RMS distance for fiducials co-located in MR and CT imaging volumes was 0.74 mm. The end-to-end error of ultrasound registration to MR imaging was 2.98 mm, as compared to 1.65 mm for CT.
  
  
  CONCLUSIONS
  Ultrasound registration to MR imaging data is a viable non-invasive alternative to point-based registration.
authors.affiliation: Institute for Computer Assisted Orthopaedic Surgery, Western Pennsylvania Hospital, Pittsburgh, PA 15224, USA. pmurtha@icaos.org
authors.forename: P E
authors.initials: PE
authors.lastname: Murtha
authors.forename: N
authors.initials: N
authors.lastname: Watterson
authors.forename: C
authors.initials: C
authors.lastname: Nikou
authors.forename: B
authors.initials: B
authors.lastname: Jaramaz
mesh_terms: D000465:Algorithms; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007719:Knee Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014463:Ultrasonography / Q000379:methods*