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) from an area ratio obtained from only one slice (%EL) or from three slices (%EL). The %EL calculated from a time-consuming measurement on all magnetic resonance (MR) slices, was compared to the %EL and the %EL.

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 values in the cochlea and the vestibule were measured separately by two observers. The correlations between the %EL or the %EL and the %EL values were evaluated.

Results: A strong linear correlation was observed between the %EL and the %EL or the %EL 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 and the %EL or the %EL 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, the %EL and the %EL.

Conclusion: The %EL might be easily estimated from the %EL or the %EL.