HIGH-RESOLUTION T2-WEIGHTED MR-IMAGING OF THE INNER-EAR USING A LONG ECHO-TRAIN-LENGTH 3D EAST SPIN-ECHO SEQUENCE

The purpose of this study was to assess the value of a long echo-train -length 3D fast spin-echo (3D-FSE) sequence in visualizing the inner e ar structures. Ten normal ears and 50 patient ears were imaged on a 1. 5 T MR unit using a head coil. Axial high-resolution T2-weighted image s of the inner ear and the internal auditory canal (IAC) were obtained in 15 min. In normal ears the reliability of the visualization for th e inner ear structures was evaluated on original images and the target ed maximum intensity projection (MIP) images of the labyrinth. In ten normal ears, 3D surface display (3D) images were also created and comp ared with MIP images. On the original images the cochlear aqueduct, th e vessels in the vicinity of the IAC, adn more than three branches of the cranial nerves were visualized in the IAC in all the ears. The vis ibility of the endolymphatic duct was 80%. On the MIP images the visib ility of the three semicircular canals, anterior and posterior ampulla , and of more than two turns of the cochlea was 100%. The MIP images a nd 3D images were almost comparable. The visibility of the endolymphat ic duct was 80% in normal ears and 0% in the affected ears of the pati ents with Meniere's disease (p < 0.01). In one patient ear a small int racanalicular tumor was depicted clearly. In conclusion, the long echo train length T2-weighted 3D-FSE sequence enables the detailed visuali zation of the tiny structures of the inner ear and the IAC within a cl inically acceptable scan time. Furthermore, obtaining a high contrast between the soft/bony tissue and the cerebrospinal/endolymph/perilymph fluid would be of significant value in the diagnosis of the pathologi c conditions around the labyrinth and the IAC.