title: Submillimetric target-registration error using a novel, non-invasive fiducial system for image-guided otologic surgery.
abstract: OBJECTIVE
  Otologic surgery is undertaken to treat ailments of the ear, including persistent infections, hearing loss, vertigo, and cancer. Typically performed on otherwise-healthy patients in outpatient facilities, the application of image-guided surgery (IGS) has been limited because accurate (<1 mm), non-invasive fiducial systems for otologic surgery have not been available. We now present such a fiducial system.
  
  
  METHODS
  A dental bite-block was fitted with a custom-designed rigid frame with 7 fiducial markers surrounding each external ear. The bones containing the ear (i.e., the temporal bones) of 3 cadaveric skulls were removed and replaced with discs containing 13 surgical targets arranged in a cross-hair pattern about the centroid of each ear. The surgical targets (26/skull) and fiducial markers (14/skull) were identified both within CT scans using a published algorithm and in physical space using an infrared optical tracking system. Fiducial registration error (FRE), fiducial localization error (FLE), and target registration error (TRE) were calculated.
  
  
  RESULTS
  For all trials, root mean square FRE = 0.66, FLE = 0.72, and TRE = 0.77 mm. The mean TRE for n = 234 independent targets was 0.73 with a standard deviation of 0.25 mm.
  
  
  CONCLUSIONS
  Using a novel, non-invasive fiducial system (the EarMark), submillimetric accuracy was repeatably achieved. This system will facilitate image-guided otologic surgery.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Vanderbilt University Medical Center, Nashville, TN 37232-2559, USA. robert.labadie@vanderbilt.edu
authors.forename: Robert F
authors.initials: RF
authors.lastname: Labadie
authors.forename: Rohan J
authors.initials: RJ
authors.lastname: Shah
authors.forename: Steve S
authors.initials: SS
authors.lastname: Harris
authors.forename: Ebru
authors.initials: E
authors.lastname: Cetinkaya
authors.forename: David S
authors.initials: DS
authors.lastname: Haynes
authors.forename: Michael R
authors.initials: MR
authors.lastname: Fenlon
authors.forename: Andrzej S
authors.initials: AS
authors.lastname: Juscyzk
authors.forename: Robert L
authors.initials: RL
authors.lastname: Galloway
authors.forename: J Michael
authors.initials: JM
authors.lastname: Fitzpatrick
mesh_terms: D016477:Artifacts; D006801:Humans; D008437:Maxilla / Q000000981:diagnostic imaging / Q000601:surgery; D008953:Models, Anatomic; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D013506:Otologic Surgical Procedures; D019047:Phantoms, Imaging; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed