title: Safety margins in robotic bone milling: from registration uncertainty to statistically safe surgeries.
abstract: BACKGROUND
  When robots mill bone near critical structures, safety margins are used to reduce the risk of accidental damage due to inaccurate registration. These margins are typically set heuristically with uniform thickness, which does not reflect the anisotropy and spatial variance of registration error.
  
  
  METHODS
  A method is described to generate spatially varying safety margins around vital anatomy using statistical models of registration uncertainty. Numerical simulations are used to determine the margin geometry that matches a safety threshold specified by the surgeon.
  
  
  RESULTS
  The algorithm was applied to CT scans of five temporal bones in the context of mastoidectomy, a common bone milling procedure in ear surgery that must approach vital nerves. Safety margins were generated that satisfied the specified safety levels in every case.
  
  
  CONCLUSIONS
  Patient safety in image-guided surgery can be increased by incorporating statistical models of registration uncertainty in the generation of safety margins around vital anatomy.
authors.affiliation: Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Siebold
authors.affiliation: Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Neal P
authors.initials: NP
authors.lastname: Dillon
authors.affiliation: Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Loris
authors.initials: L
authors.lastname: Fichera
authors.affiliation: Department of Otolaryngology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Labadie
authors.affiliation: Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Webster
authors.affiliation: Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Fitzpatrick
mesh_terms: D000465:Algorithms; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000601:surgery*; D003198:Computer Simulation; D006801:Humans; D000074406:Mastoidectomy / Q000009:adverse effects / Q000379:methods / Q000706:statistics & numerical data; D008953:Models, Anatomic; D015233:Models, Statistical; D065287:Robotic Surgical Procedures / Q000009:adverse effects / Q000706:statistics & numerical data*; D012449:Safety; D025321:Surgery, Computer-Assisted / Q000009:adverse effects / Q000706:statistics & numerical data; D014057:Tomography, X-Ray Computed; D035501:Uncertainty
keywords: image guidance; mastoidectomy; path planning; registration; robotic surgery; target registration error