title: New prototype neuronavigation system based on preoperative imaging and intraoperative freehand ultrasound: system description and validation.
abstract: OBJECTIVE
  The aim of this report is to present IBIS (Interactive Brain Imaging System) NeuroNav, a new prototype neuronavigation system that has been developed in our research laboratory over the past decade that uses tracked intraoperative ultrasound to address surgical navigation issues related to brain shift. The unique feature of the system is its ability, when needed, to improve the initial patient-to-preoperative image alignment based on the intraoperative ultrasound data. Parts of IBIS Neuronav source code are now publicly available on-line.
  
  
  METHODS
  Four aspects of the system are characterized in this paper: the ultrasound probe calibration, the temporal calibration, the patient-to-image registration and the MRI-ultrasound registration. In order to characterize its real clinical precision and accuracy, the system was tested in a series of adult brain tumor cases.
  
  
  RESULTS
  Three metrics were computed to evaluate the precision and accuracy of the ultrasound calibration. 1) Reproducibility: 1.77 mm and 1.65 mm for the bottom corners of the ultrasound image, 2) point reconstruction precision 0.62-0.90 mm: and 3) point reconstruction accuracy: 0.49-0.74 mm. The temporal calibration error was estimated to be 0.82 ms. The mean fiducial registration error (FRE) of the homologous-point-based patient-to-MRI registration for our clinical data is 4.9 ± 1.1 mm. After the skin landmark-based registration, the mean misalignment between the ultrasound and MR images in the tumor region is 6.1 ± 3.4 mm.
  
  
  CONCLUSIONS
  The components and functionality of a new prototype system are described and its precision and accuracy evaluated. It was found to have an accuracy similar to other comparable systems in the literature.
authors.affiliation: McConnell Brain Imaging Center, Montreal Neurological Institute, McGill University, Montreal, QC, Canada. laurence@bic.mni.mcgill.ca
authors.forename: Laurence
authors.initials: L
authors.lastname: Mercier
authors.forename: Rolando F
authors.initials: RF
authors.lastname: Del Maestro
authors.forename: Kevin
authors.initials: K
authors.lastname: Petrecca
authors.forename: Anna
authors.initials: A
authors.lastname: Kochanowska
authors.forename: Simon
authors.initials: S
authors.lastname: Drouin
authors.forename: Charles X B
authors.initials: CX
authors.lastname: Yan
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Janke
authors.forename: Sean Jy-Shyang
authors.initials: SJ
authors.lastname: Chen
authors.forename: D Louis
authors.initials: DL
authors.lastname: Collins
mesh_terms: D000328:Adult; D001921:Brain / Q000601:surgery*; D001932:Brain Neoplasms / Q000175:diagnosis / Q000601:surgery*; D004867:Equipment Design; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D038361:Neuronavigation / Q000295:instrumentation*; D019635:Neurosurgical Procedures; D011300:Preoperative Care / Q000379:methods*; D017585:Ultrasonography, Doppler, Transcranial / Q000295:instrumentation*; D014584:User-Computer Interface