title: Reduced risk trajectory planning in image-guided keyhole neurosurgery.
abstract: OBJECTIVE
  The authors present and evaluate a new preoperative planning method and computer software designed to reduce the risk of candidate trajectories for straight rigid tool insertion in image-guided keyhole neurosurgery.
  
  
  METHODS
  Trajectories are computed based on the surgeon-defined target and a candidate entry point area on the outer head surface on preoperative CT/MRI scans. A multiparameter risk card provides an estimate of the risk of each trajectory according to its proximity to critical brain structures. Candidate entry points in the outer head surface areas are then color-coded and displayed in 3D to facilitate selection of the most adequate point. The surgeon then defines and/or revised the insertion trajectory using an interactive 3D visualization of surrounding structures. A safety zone around the selected trajectory is also computed to visualize the expected worst-case deviation from the planned insertion trajectory based on tool placement errors in previous surgeries.
  
  
  RESULTS
  A retrospective comparative study for ten selected targets on MRI head scans for eight patients showed a significant reduction in insertion trajectory risk. Using the authors' method, trajectories longer than 30 mm were an average of 2.6 mm further from blood vessels compared to the conventional manual method. Average planning times were 8.4 and 5.9 min for the conventional technique and the authors' method, respectively. Neurosurgeons reported improved understanding of possible risks and spatial relations for the trajectory and patient anatomy.
  
  
  CONCLUSIONS
  The suggested method may result in safer trajectories, shorter preoperative planning time, and improved understanding of risks and possible complications in keyhole neurosurgery.
authors.affiliation: School of Engineering and Computer Science, The Hebrew University of Jerusalem, 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: Idit
authors.initials: I
authors.lastname: Tamir
authors.forename: Elad
authors.initials: E
authors.lastname: Dabool
authors.forename: Lihi
authors.initials: L
authors.lastname: Pertman
authors.forename: Adam
authors.initials: A
authors.lastname: Ben-Ami
authors.forename: Yigal
authors.initials: Y
authors.lastname: Shoshan
mesh_terms: D006801:Humans; D008279:Magnetic Resonance Imaging; D009493:Neurosurgery / Q000379:methods*; D057234:Preoperative Period; D012306:Risk; D012449:Safety; D012984:Software; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed