title: Localization and registration accuracy in image guided neurosurgery: a clinical study.
abstract: OBJECTIVE
  To measure and compare the clinical localization and registration errors in image-guided neurosurgery, with the purpose of revising current assumptions.
  
  
  METHODS
  Twelve patients who underwent brain surgeries with a navigation system were randomly selected. A neurosurgeon localized and correlated the landmarks on preoperative MRI images and on the intraoperative physical anatomy with a tracked pointer. In the laboratory, we generated 612 scenarios in which one landmark pair was defined as the target and the remaining ones were used to compute the registration transformation. Four errors were measured: (1) fiducial localization error (FLE); (2) target registration error (TRE); (3) fiducial registration error (FRE); (4) Fitzpatrick's target registration error estimation (F-TRE). We compared the different errors and computed their correlation.
  
  
  RESULTS
  The image and physical FLE ranges were 0.5-2.0 and 1.6-3.0 mm, respectively. The measured TRE, FRE and F-TRE were 4.1 +/- 1.6, 3.9 +/- 1.2, and 3.7 +/- 2.2 mm, respectively. Low correlations of 0.19 and 0.37 were observed between the FRE and TRE and between the F-TRE and the TRE, respectively. The differences of the FRE and F-TRE from the TRE were 1.3 +/- 1.0 mm (max = 5.5 mm) and 1.3 +/- 1.2 mm (max = 7.3 mm), respectively.
  
  
  CONCLUSIONS
  Contrary to common belief, the FLE presents significant variations. Moreover, both the FRE and the F-TRE are poor indicators of the TRE in image-to-patient registration.
authors.affiliation: School of Engineering and Computer Science, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel. rubke@cs.huji.ac.il
authors.forename: Reuben R
authors.initials: RR
authors.lastname: Shamir
authors.forename: Leo
authors.initials: L
authors.lastname: Joskowicz
authors.forename: Sergey
authors.initials: S
authors.lastname: Spektor
authors.forename: Yigal
authors.initials: Y
authors.lastname: Shoshan
mesh_terms: D000465:Algorithms; D001921:Brain / Q000473:pathology* / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging; D038361:Neuronavigation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results