title: Fiducial versus nonfiducial neuronavigation registration assessment and considerations of accuracy.
abstract: OBJECTIVE
  For frameless stereotaxy, users can choose between anatomic landmarks (ALs) or surface fiducial markers (FMs) for their match points during registration to define an alignment of the head in the physical and radiographic image space. In this study, we sought to determine the concordance among a point-merged FM registration, a point-merged AL registration, and a combined point-merged anatomic/surface-merged (SM) registration, i.e., to determine the accuracy of registration techniques with and without FMs by examining the extent of agreement between the system-generated predicted value and physical measured values.
  
  
  METHODS
  We examined 30 volunteers treated with gamma knife surgery. The frameless stereotactic image-guidance system called the StealthStation (Medtronic Surgical Navigation Technologies, Louisville, CO) was used. Nine FMs were placed on the patient's head and four were placed on a Leksell frame rod-box, which acted as a rigid set to determine the difference in error. For each registration form, we recorded the generated measurement (GM) and the physical measurement (PM) to each of the four checkpoint FMs. Bland and Altman plot difference analyses were used to compare measurement techniques. Correlations and descriptive analyses were completed.
  
  
  RESULTS
  The mean of values for GMs were 1.14 mm for FM, 2.3 mm for AL, and 0.96 mm for SM registrations. The mean errors of the checkpoints were 3.49 mm for FM, 3.96 mm for AL, and 3.33 mm for SM registrations. The correlation between GMs and PMs indicated a linear relationship for all three methods. AL registration demonstrated the greatest mean difference, followed by FM registration; SM registration had the smallest difference between GMs and PMs. Differences in the anatomic registration methods, including SM registration, compared with FM registration were within a mean +/- 1.96 (standard deviation) according to the Bland and Altman analysis.
  
  
  CONCLUSIONS
  For our sample of 30 patients, all three registration methods provided comparable distances to the target tissue for surgical procedures. Users may safely choose anatomic registration as a less costly and more time-efficient registration method for frameless stereotaxy.
authors.affiliation: Neurosurgery Research Laboratory, Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors.forename: Wolfgang K
authors.initials: WK
authors.lastname: Pfisterer
authors.forename: Stephen
authors.initials: S
authors.lastname: Papadopoulos
authors.forename: Denise A
authors.initials: DA
authors.lastname: Drumm
authors.forename: Kris
authors.initials: K
authors.lastname: Smith
authors.forename: Mark C
authors.initials: MC
authors.lastname: Preul
mesh_terms: D006801:Humans; D004867:Equipment Design; D019544:Equipment Failure Analysis; D038361:Neuronavigation / Q000295:instrumentation / Q000379:methods; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique