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AJNR - American Journal of Neuroradiology

Published ahead of print on October 18, 2007
doi: 10.3174/ajnr.A0735

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Comparison of 45° Oblique Reformats with Axial Reformats in CT Evaluation of the Vestibular Aqueduct

B. Ozgen^a, M.E. Cunnane^b, P.A. Caruso^b and H.D. Curtin^b

^a Department of Radiology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
^b Massachusetts Eye and Ear Infirmary, Boston, Mass

View larger version (152K): [in this window] [in a new window]   Fig 1. Reformatted image of a CT of the temporal bone in the 45° oblique plane, demonstrating the position of the vestibular aqueduct.

View larger version (61K): [in this window] [in a new window]   Fig 2. Planning of the axial reformats based on the sagittal scout image. Axial reformats were obtained parallel to the axis of the cochlea (A). The obtained axial reformat demonstrates the vestibular aqueduct (arrow) (B).

View larger version (79K): [in this window] [in a new window]   Fig 3. Planning of the 45° oblique reformats based on the axial scout image. The 45° oblique reformats were obtained parallel to the plane of the SSC (A). The obtained reformat demonstrates the vestibular aqueduct (arrow) (B).

View larger version (161K): [in this window] [in a new window]   Fig 4. Grading of the aqueductal visibility. In 1 patient, there is a grade 3 well-visualized aqueduct in both 45° oblique (A) and axial (B) reformats. In another patient, the vestibular aqueduct is judged to be grade 2 (thin but visible) in 45° oblique formats (C), and grade 1 (difficult to see/very thin) on axial reformats (D).

View larger version (59K): [in this window] [in a new window]   Fig 5. Measurement of the aqueducts: positioning of the measurement bars at the 2 described levels (midportion of the postisthmic segment and external aperture) in (A) and in axial (B, C) reformats.

View larger version (162K): [in this window] [in a new window]   Fig 6. Diagram demonstrating the plane of the axial image across the vestibular aqueduct on the 45° oblique reformat. A line is drawn connecting 2 points of the lateral semicircular canal. This line demonstrates the obliquity of the axial reformat to the axis of the vestibular aqueduct.