The value of magnetic resonance imaging (MRI) in the diagnosis of
acoustic tumors was retrospectively assessed in 38 cases. A 0.15 Tesla permanent magnet and a 1.5 Tesla superconducting magnet were employed in 24 and 14 cases, respectively.
Gadolinium diethylene triamine pentaacetic
acid (
Gd-DTPA), a paramagnetic
contrast agent, was used in 10 cases.
Acoustic tumors were identified in all cases. Small, medium, and large
tumors were depicted with equal clarity by MRI and computed tomography (CT). However,
tumor contour and extension, accompanying
cysts, and brainstem displacement were more clearly visualized on MRI. The use of
Gd-DTPA improved the quality of the MR images by markedly enhancing the
acoustic tumors in all cases. In particular, detection of small
acoustic tumors and intra- or paratumoral
cysts was facilitated by the use of
Gd-DTPA. The possibility of a correlation between
acoustic tumor histology and MRI features was studied by calculation of the contrast to noise (C/N) ratio in 10 cases of
acoustic tumor and 7 cases of
meningioma. No definite correlation was demonstrated, but there appeared to be some difference in the C/N ratio between
acoustic tumors and
meningiomas. In three volunteers, MRI demonstrated intracanalicular nerves, separately. Because of its higher resolution, MRI can be expected to replace CT and air CT in the diagnosis of
acoustic tumors.