Simple Estimation of the Endolymphatic Volume Ratio after Intravenous Administration of a Single-dose of Gadolinium Contrast

PURPOSE: To evaluate the feasibility of a simple estimation for the endolymphatic volume ratio (endolymph volume/total lymph volume = %EL(volume)) from an area ratio obtained from only one slice (%EL(1slice)) or from three slices (%EL(3slices)). The %EL(volume,) calculated from a time-consuming measurement on all magnetic resonance (MR) slices, was compared to the %EL(1slice) and the %EL(3slices). METHODS: In 40 ears of 20 patients with a clinical suspicion of endolymphatic hydrops, MR imaging was performed 4 hours after intravenous administration of a single dose of gadolinium-based contrast material (IV-SD-GBCM). Using previously reported HYDROPS2-Mi2 MR imaging, the %EL(volume) values in the cochlea and the vestibule were measured separately by two observers. The correlations between the %EL(1slice) or the %EL(3slices) and the %EL(volume) values were evaluated. RESULTS: A strong linear correlation was observed between the %EL(volume) and the %EL(3slices) or the %EL(1slice) in the cochlea. The Pearson correlation coefficient (r) was 0.968 (3 slices) and 0.965 (1 slice) for observer A, and 0.968 (3 slices) and 0.964 (1 slice) for observer B (P < 0.001, for all). A strong linear correlation was also observed between the %EL(volume) and the %EL(3slices) or the %EL(1slice) in the vestibule. The Pearson correlation coefficient (r) was 0.980 (3 slices) and 0.953 (1 slice) for observer A, and 0.979 (3 slices) and 0.952 (1 slice) for observer B (P < 0.001, for all). The high intra-class correlation coefficients (0.991–0.997) between the endolymph volume ratios by two observers were observed in both the cochlea and the vestibule for values of the %EL(volume), the %EL(3slices) and the %EL(1slice). CONCLUSION: The %EL(volume) might be easily estimated from the %EL(3slices) or the %EL(1slice).