Anatomic evaluation of the membranous labyrinth by imaging: 3D-MRI volume-rendered reconstructions

Recent advances in magnetic resonance imaging (MRI) technology has allowed the development of imaging sequences tailored to the assessment of minute anatomic detail of the temporal bone structures. Volume Rendering (VR) is a 3D rendering method used in MRI. It helps in understanding complex anatomic conditions and is particularly useful in the evaluation of tiny structures as the membranous labyrinth. The authors aimed at verifying the contribution of VR in the study of labyrinthine pathology in view of all the possible anatomic correlation.

We performed 3D T2-weighted FSE MRI at 1.5 T with a dedicated surface coil, at high resolution (0.5 mm partition). All selected patients were volunteers and unknown for temporal bone pathology.

The anatomy of the cochlea and vestibule were clearly defined. We could distinguish components of the cochlea to the level of the scala tympani, the vestibule and the cochlear duct. The saccule, utricle, endolymphatic duct and sac, and semicircular canals were also distinguished.

Volume reconstructions yielded excellent spatial information regarding the cochlea, vestibule, semicircular canals and all three ampullae. Maximum Intensity Projection (MIP) images are useful as a preliminary study, to show eventual inner acoustic canal pathology and to provide information with the use of contrasting agents. We conclude therefore that VR seems to be essential in evaluating labyrinthine anatomy and pathology. Our results suggest that improved diagnostic information can be obtained by applying this volume visualization reconstruction technique in all inner ear neuroradiological protocols.