3-T Imaging of the Cochlear Nerve and Labyrinth in Cochlear-Implant Candidates: 3D Fast Recovery Fast Spin-Echo versus 3D Constructive Interference in the Steady State Techniques
John I. Lanea,
Heidi Warda,
Robert J. Wittea,
Matt A. Bernsteina and
Colin L. W. Driscollb
a Department of Radiology, Mayo Clinic, Rochester, MN
b Department of Otolaryngology, Mayo Clinic, Rochester, MN
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FIG 1. Comparison of the IAC on oblique sagittal images.
A, Two-phase–cycled, 3D CISS reconstructed image oriented perpendicular to the long axis of the cochlear nerve demonstrates excellent signal intensity in the IAC good definition of all four nerves.
B, 3D FRFSE image demonstrates less intense CSF signal with greater background noise. Nerve definition is satisfactory.
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FIG 2. Comparison of a small IAC on oblique sagittal images.
A, 3D CISS image demonstrates satisfactory nerve definition within the IAC despite the small caliber of the bony canal. Note CSF surrounding the cochlear nerve (arrow).
B, 3D FRFSE image shows relatively low CSF signal intensity and high background noise. Note the loss of CSF signal intensity around the cochlear nerve (arrow).
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FIG 3. Comparison of the spiral lamina and the modiolus of the cochlea on oblique sagittal images..
A and B, 3D CISS (A) and 3D FRFSE (B) images demonstrate a linear focus of decreased signal intensity that represents the spiral lamina (arrow).
C and D, 3D CISS (C) and 3D FRFSE (D) images demonstrate the modiolus (arrow).
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FIG 4. Comparison of the semicircular canal and its apex (arrow) on oblique sagittal images.
A, 3D CISS reformatted in the plane of the superior semicircular canal (SSC) demonstrates excellent definition of fluid in the apex.
B, Volume-rendered maximum intensity projection (MIP) of A shows intact fluid rings in all semicircular canals.
C, 3D FRFSE image also reformatted in the plane of the SCC demonstrates signal intensity loss at the apex.
D, Volume-rendered MIP of D also depicts this finding.
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FIG 5. Comparison of the FNC (arrow) on oblique sagittal images.
A, 3D CISS image adequately displays the normal course of the FNC.
B, Corresponding 3D FRFSE image shows considerably less signal intensity.
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FIG 6. Comparison of the endolymphatic duct on oblique sagittal images.
A, 3D CISS demonstrates modest signal intensity in the normal small endolymphatic duct in the vestibular aqueduct, which is seen just medial to the common crus of the superior and posterior SSCs (arrow).
B, The duct (arrow) is barely identifiable on the corresponding 3D-FRFSE image. The window and level may need to be adjusted to visualize this normally small duct, which is often not visualized with either technique.
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FIG 7. 3D CISS banding artifact.
A, Oblique sagittal source image from two-phase–cycled 3D CISS demonstrates marked banding artifact through the SSC and vestibule (arrow).
B, Postprocessed MIP image at the same level demonstrates subtle irregularity of the contour of the SCC, which represents incomplete averaging of the banding artifact (arrow).
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FIG 8. Motion artifact between phase cycles on 3D CISS images. Postprocessed MIP image fails to remove banding artifact secondary to patient motion during data acquisition (arrow).
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