title: Validation of a stereo camera system to quantify brain deformation due to breathing and pulsatility.
abstract: OBJECTIVE
  A new stereo vision system is presented to quantify brain shift and pulsatility in open-skull neurosurgeries.
  
  
  METHODS
  The system is endowed with hardware and software synchronous image acquisition with timestamp embedding in the captured images, a brain surface oriented feature detection, and a tracking subroutine robust to occlusions and outliers. A validation experiment for the stereo vision system was conducted against a gold-standard optical tracking system, Optotrak CERTUS. A static and dynamic analysis of the stereo camera tracking error was performed tracking a customized object in different positions, orientations, linear, and angular speeds.
  
  
  RESULTS
  The system is able to detect an immobile object position and orientation with a maximum error of 0.5 mm and 1.6° in all depth of field, and tracking a moving object until 3 mm/s with a median error of 0.5 mm. Three stereo video acquisitions were recorded from a patient, immediately after the craniotomy. The cortical pulsatile motion was captured and is represented in the time and frequency domain. The amplitude of motion of the cloud of features' center of mass was inferior to 0.8 mm. Three distinct peaks are identified in the fast Fourier transform analysis related to the sympathovagal balance, breathing, and blood pressure with 0.03-0.05, 0.2, and 1 Hz, respectively.
  
  
  CONCLUSIONS
  The stereo vision system presented is a precise and robust system to measure brain shift and pulsatility with an accuracy superior to other reported systems.
authors.affiliation: MARLab - Department of Industrial Electronics and Centre Algoritmi, Universidade do Minho, 4800-058 Guimarães, Portugal.
authors.forename: Carlos
authors.initials: C
authors.lastname: Faria
authors.affiliation: Medical Robotics Laboratory - Mechanical Engineering Department, Technion - Israel Institute of Technology, 32000 Haifa, Israel.
authors.forename: Ofri
authors.initials: O
authors.lastname: Sadowsky
authors.affiliation: MARLab - Department of Industrial Electronics and Centre Algoritmi, Universidade do Minho, 4800-058 Guimarães, Portugal.
authors.forename: Estela
authors.initials: E
authors.lastname: Bicho
authors.affiliation: NearLab - Department of Electronics, Information and Bioengineering, Politecnico di Milano, 20133 Milano, Italy.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Ferrigno
authors.affiliation: School of Engineering and Computer Science, Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Leo
authors.initials: L
authors.lastname: Joskowicz
authors.affiliation: Medical Robotics Laboratory - Mechanical Engineering Department, Technion - Israel Institute of Technology, 32000 Haifa, Israel.
authors.forename: Moshe
authors.initials: M
authors.lastname: Shoham
authors.affiliation: School of Engineering and Computer Science, Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Refael
authors.initials: R
authors.lastname: Vivanti
authors.affiliation: NearLab - Department of Electronics, Information and Bioengineering, Politecnico di Milano, 20133 Milano, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: De Momi
mesh_terms: D000465:Algorithms; D001921:Brain / Q000473:pathology; D002138:Calibration; D003399:Craniotomy; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D009068:Movement; D009493:Neurosurgery / Q000379:methods*; D055095:Optics and Photonics; D015203:Reproducibility of Results; D012119:Respiration; D012886:Skull / Q000473:pathology / Q000601:surgery*; D012984:Software; D014741:Video Recording