Labyrinthine Signal Intensity on Non-contrast-enhanced 3D-real Inversion Recovery MR Imaging: Correlation with the Endolymphatic Volume Measured on Contrast-enhanced HYDROPS-Mi2.

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.