MR imaging of the acoustic nerves and small XXXX at 0.6 T: prospective study.

@entity1 @entity5513 @entity5 @entity2103 @entity1504 @entity302 @entity393 @entity28540 @entity9468
To evaluate the capability of magnetic resonance (MR) in imaging normal acoustic nerves, 12 volunteers without signs or symptoms of @entity1504 were examined using a 0.6 T superconductive system. Several @entity9468 ( @entity9468 ) pulse sequences were tested to identify the optimal sequence for demonstration of the acoustic nerve bundle. Repetition times (TRs) varied from 300 to 2000 msec and echo times (TEs) from 30 to 120 msec. A single-slice technique was used with 5 and 8 mm sections, one or two data acquisitions per projection, and axial and coronal imaging. The normal acoustic nerves were demonstrated readily by MR in axial and/or coronal sections. The distal parts of the nerves and @entity5 were imaged best with @entity9468 1500/60. The @entity2103 tended to be obscured in this sequence by brightening the cerebrospinal fluid signal adjacent to the brainstem, but they were demonstrated clearly with 500 or 800 msec TR and 30 msec TE. Five @entity1 were studied who had @entity393 and evidence of @entity28540 . In four @entity1 , MR imaging demonstrated five acoustic nerve @entity5 ranging in size from purely intracanalicular to a 12 mm cisternal component. In the fifth case, no @entity5 was identified by MR imaging or gas computed tomographic (CT) cisternography. Contrast-enhanced CT using a Siemens Somatom DR 3 or GE CT/T 8800 scanner failed to provide convincing evidence of @entity5 in any case, while gas CT cisternography was positive in all five @entity5 . All five @entity5513 were identified readily using the @entity9468 sequences that proved optimal for demonstration of normal nerves. This experience revealed that MR imaging can demonstrate the eighth nerve complex well and reliably. @entity302 (5 or 8 mm) technique is adequate, but multislice without tissue gaps (used recently) is more efficient. Small, even intracanalicular, @entity5513 are imaged effectively, indicating that the method is capable of superseding contrast CT cisternography, particularly with improving technology.
