title: Estimation of the endolymphatic sac and vestibular aqueduct using magnetic resonance imaging.
abstract: OBJECTIVE
  To evaluate the diagnostic accuracy of magnetic resonance imaging for assessment of the endolymphatic sac and vestibular aqueduct.
  
  
  METHODS
  Imaging and histological study of the cadaver.
  
  
  METHODS
  Five cadavers were studied by a 1.5-T magnetic resonance imaging system with a 3-inch-diameter surface coil. Magnetic resonance imaging scans were obtained with proton density-weighted and T2-weighted fast spin-echo sequences. Histological sections were made with an epoxy resin-embedding method and were compared with magnetic resonance imaging scans.
  
  
  RESULTS
  The visibility of the endolymphatic sac on both sequences corresponded well to the presence of the endolymphatic sac on histological sections. On the histological sections, the width of the external aperture of vestibular aqueduct (endolymphatic sac including surrounding connective tissue) was 0.96 +/- 0.18 mm (mean +/- SD) and the width of lumen of endolymphatic sac at the same point was 0.47 +/- 0.17 mm. The width of the endolymphatic sac was 1.02 +/- 0.19 mm on proton density-weighted images and was 0.81 +/- 0.15 mm on T2-weighted images. The widths of endolymphatic sac measured on proton density-weighted image and those of vestibular aqueduct on histological section did not show statistically significant differences (P >.05). On the other hand, the endolymphatic sac as measured on T2-weighted image tended to be smaller than the vestibular aqueduct (P <.05) and tended to be larger than the lumen of the endolymphatic sac (P <.0005).
  
  
  CONCLUSIONS
  Both sequences can precisely depict the endolymphatic sac; however, the proton density-weighted image is a more appropriate indicator of the actual anatomical configuration of the endolymphatic sac with surrounding connective tissue and vestibular aqueduct.
authors.affiliation: Department of Otolaryngology, School of Medicine, Tokyo Medical and Dental University, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Atsunobu
authors.initials: A
authors.lastname: Tsunoda
authors.forename: Keiichi
authors.initials: K
authors.lastname: Akita
authors.forename: Ichiro
authors.initials: I
authors.lastname: Yamada
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003238:Connective Tissue / Q000033:anatomy & histology; D004711:Endolymphatic Duct / Q000033:anatomy & histology; D004712:Endolymphatic Sac / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012665:Semicircular Canals / Q000033:anatomy & histology; D012680:Sensitivity and Specificity; D014723:Vestibular Aqueduct / Q000033:anatomy & histology*