Article ID: mp.2025-0068
Purpose: To investigate the relationship between the signal intensity (SI) of the entire labyrinthine fluid on non–contrast-enhanced 3D real inversion recovery (3D–real IR) imaging and the endolymphatic volume measured on contrast-enhanced HYDROPS-Mi2 (HYbriD of Reversed image Of Positive endolymph signal and native image of positive perilymph Signal image Multiplied with hT2w MR cisternography) imaging.
Methods: This retrospective study included 37 patients (74 ears) with suspected endolymphatic hydrops (EH). The volume ratio of the endolymphatic space (%ELvol) was measured on contrast-enhanced HYDROPS-Mi2 images, and the normalized volume-averaged signal intensity (nSIvol) of the entire labyrinthine fluid was measured on non–contrast-enhanced 3D–real IR images. Statistical analyses included comparisons of nSIvol between the cochlea and vestibule, side-to-side differences in EH-negative ears, paired comparisons of nSIvol between larger- and smaller-%ELvol sides, correlations between %ELvol and nSIvol, and receiver operating characteristic (ROC) curve analysis of nSIvol for discriminating severe from mild/no EH. The presence of EH was defined based on the clinical diagnosis using Nakashima grading.
Results: The vestibular %ELvol was significantly higher and the vestibular nSIvol significantly lower than that in the cochlea (both P < 0.001). In EH-negative ears, no significant side-to-side difference in nSIvol was observed. In both cochleae and vestibules, nSIvol was significantly lower on the larger-%ELvol side than on the smaller-%ELvol side (cochlea: P = 0.002; vestibule: P = 0.007). Significant negative correlations between %ELvol and nSIvol were observed in both the cochlea (Spearman’s rank correlation coefficient [Rs] = –0.598, P < 0.001) and vestibule (Rs = –0.417, P < 0.001). The area under the ROC curve was 0.827 in the cochlea, and 0.698 in the vestibule.
Conclusion: The SI of the entire labyrinthine fluid measured on non–contrast-enhanced 3D–real IR imaging showed a significant negative correlation with the endolymphatic volume measured on contrast-enhanced HYDROPS-Mi2. These findings suggest that the SI of labyrinthine fluid, as measured on non–contrast-enhanced 3D–real IR images, may serve as an indirect indicator for estimating the degree of EH.
