Visualization of endolymphatic hydrops using magnetic resonance imaging at 3 tesla in Osaka University

Abstract

Visualization of endolymphatic hydrops (EH) by magnetic resonance imaging (MRI) is becoming increasingly important and popular for the diagnosis of various inner ear diseases, such as Meniere's disease. However, most studies have been performed using Siemens scanners. At Osaka University, we have been using General Electric (GE) scanners at 3 Tesla for imaging EH since 2007. Both the scanning protocols of 24 h after intratympanic administration of gadolinium (Gd) and 4 h after intravenous injection of Gd are used. In contrast to the Siemens system, in which MRI sequences specific for EH imaging are available, we use the conventional two-dimensional fluid-attenuated inversion-recovery (2 DFLAIR) and three-dimensional fast imaging sequences employing steady state acquisition (FIESTA, also known as "cisternography") to acquire axial images of the inner ear of 2-mm and 0.5-mm thickness, respectively. Written informed consent is obtained from the patients before the imagings. The examinations are performed in compliance with the Declaration of Helsinki and are approved by the institutional ethics committee. In total, 76 patients have undergone MRI under various clinical situations, such as before and after sac surgery, and before intratympanic administration of gentamycin to treat Meniere's disease. The presence of hydrops is clearly detected by T 2-FLAIR images in most patients with clinical EH. Unlike the MRI sequences obtained using the Siemens system, it is currently difficult to distinguish the area of the inner ear with no enhancement (either perilymph with no contrast or endolymph) from bony areas surrounding the inner ear in our T 2- FLAIR images obtained using the GE system. Comparison between T 2-FLAIR and FIESTA sections at the same level is recommended. Three-dimensional volumetric co-registration of FIESTA images to T 2-FLAIR images is also helpful when the patient's head movements during the MRI scanning are not negligible.