title: Detection of labyrinthine fistulas in human temporal bone by virtual endoscopy and density threshold variation on computed tomographic scan.
abstract: OBJECTIVE
  To assess the sensitivity of the routine computed tomographic (CT) scan of the temporal bone coupled to a virtual endoscopy, with density threshold variation, in detecting small fistulas in human temporal bone specimens.
  
  
  METHODS
  Single-blind, before-after trial.
  
  
  METHODS
  This study was carried out in a research laboratory in collaboration with a radiology department.
  
  
  METHODS
  Five human adult temporal bone specimens were included.
  
  
  METHODS
  The fistulas were created with calibrated burrs (0.3, 0.5, and 0.8 mm) in the 3 semicircular canals and in the promontory of 3 temporal bones. Two other temporal bones served as controls. All bones underwent CT scan (1-mm section thickness) before and after dissection. Three-dimensional images were obtained from CT scan native axial views at different density reconstruction thresholds. The virtual endoscope was placed in the middle ear cavity looking to the inner ear wall. The threshold at which a bony defect appeared on virtual endoscopic images (opening threshold in Hounsfield units [H]) was noted for each location.
  
  
  METHODS
  Opening thresholds before and after dissection.
  
  
  RESULTS
  On standard axial views, fistulas smaller than 0.5 mm were not visualized. By virtual endoscopy, all fistulas could be visualized. The opening threshold decreased after fistula creation in the semicircular canals (1244 +/- 50.5 H [n = 36] vs 778 +/- 52.4 H [n = 34]; P<.001; 1-way analysis of variance and Dunnett multiple comparisons posttest) and in the promontory (1541 +/- 37.8 H [n = 12] vs 1334 +/- 35.1 H [n = 8]; P<.001). The opening thresholds in the control specimens remained unchanged after dissection.
  
  
  CONCLUSIONS
  Virtual endoscopy with variation of reconstruction threshold allows the detection of small labyrinthine fistulas with diameters of 0.3 mm or smaller.
authors.affiliation: Radiology Department, Clinique Turin, Equipe Mixte INSERM-Universite 0112, Faculté Xavier Bichat, Université Paris 7, France.
authors.forename: Jean-Loup
authors.initials: JL
authors.lastname: Bensimon
authors.forename: Alexis Bozorg
authors.initials: AB
authors.lastname: Grayeli
authors.forename: Michel
authors.initials: M
authors.lastname: Toupet
authors.forename: Evelyne
authors.initials: E
authors.lastname: Ferrary
authors.forename: Olivier
authors.initials: O
authors.lastname: Sterkers
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005402:Fistula / Q000175:diagnosis* / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D007759:Labyrinth Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging; D019720:Otoscopes; D012680:Sensitivity and Specificity; D013701:Temporal Bone; D014057:Tomography, X-Ray Computed; D014584:User-Computer Interface