Key points
Introduction
Ménière’s disease(MD)is characterized by three clinical symptoms of fluctuating low-frequency sensorineural hearing loss, tinnitus and/or aural fullness, and vertigo attacks in about 0.2–0.5 % of the general population (1,2).The diagnosis of MD is based upon the typical clinical syndrome complemented with a battery of audiological, vestibular, and electrophysiological tests and the demonstration of endolymphatic hydrops (EH)(3,4). However, the latter onewas lack of a gold standard diagnostic test, and could only be obtained by histological post-mortem examination previously.
Magnetic resonance imaging(MRI) has been reported for the potential in the clinical diagnosis of MD.After Zou et al. was the first study reportinga separate visualization of endolymph and perilymph regions in living humans using MRI (5), Nakashima et al (6)showed the feasibility of gadolinium enhanced MRI in the visualization of EH in living MD patients. With intravenous injection of gadolinium-based contrast media (GBCM), three-dimensional fluid-attenuated-inversion-recovery (3D-FLAIR) imaging hasbeen reported to visualize EH (7-11). The optimal scan time reported was 4hours after the administration of GBCM at a single-dose (0.2ml/kg)(7).The concentration of GBCM in the perilymph after single-dose intravenous injection however is too low to be detected by convention 3D-FLAIR in patients without impaired permeability of the blood labyrinthine barrier (12)and is challenging to achieve consistent gadolinium enhancement in the upper part of the cochlea (1,13), although it has been used widely in a number of clinical applications.Therefore, a higher dose of contrast agent is requested in labyrinthineimaging. Under FDA approved maximal triple dose of gadolinium (i.e. 0.3 mmol/kg) for human imaging, a double-dose injection (0.4ml/kg), aiming to obtain higher signal intensity (14), has started being applied in clinic nowadays.The optimal image contrast was however, not observed after 4 hours posta double-dose injection. Hence, it is crucial to investigate the optimal scan time at double dose administration.
On the other hand, the 3D image volume for bilateral inner ear is essential to be adjusted in three directions. While a proper adjustment in axial and coronal directions can ensure symmetrical display for bilateral inner ears, a suitable scan angle applied in sagittal view plays an important role in labyrinthine imaging.With this, the relative maximum areas of the saccule, utricle and lateral semicircular canal can thus be provided at the same level to accurately estimate the EHand judge whether EH herniation occurs in the lateral semicircular canal. However, this optimal scan angle with the anterior skull base remains unknow so far.
Therefore, this study wasto explore the optimal imaging parameters of 3D-FLAIR, including the optimal scan time at double dose administration and scan angle, in labyrinthine imaging for patients with vertigo and sensorineural hearing loss.
Materials and methods