Signal Alteration of the Cochlear Perilymph on 3 Different Sequences after Intratympanic Gd-DTPA Administration at 3 Tesla: Comparison of 3D-FLAIR, 3D-T1-weighted Imaging, and 3D-CISS

Purpose: Three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) imaging after intratympanic gadolinium injection is useful for pathophysiologic and morphologic analysis of the inner ear. However, statistical analysis of differences in inner ear signal intensity among 3D-FLAIR and other sequences has not been reported. We evaluated the signal intensity of cochlear fluid on each of 3D-FLAIR, 3D-T-1-weighted imaging (T1WI), and 3D-constructive interference in the steady state (CISS) to clarify the differences in contrast effect among these 3 sequences using intratympanic gadolinium injection. Methods: Twenty-one patients underwent 3D-FLAIR, 3D-T1WI, and 3D-CISS imaging at 3 tesla 24 hours after intratympanic injection of gadolinium. We determined regions of interest of the cochleae (C) and medulla oblongata (M) on each image, evaluated the signal intensity ratio between C and M (CM ratio), and determined the ratio of cochlear signal intensity of the injected side to that of the non-injected side (contrast value). Results: The CM ratio of the injected side (3.00 +/- 1.31, range, 0.53 to 4.88, on 3D-FLAIR; 0.83 +/- 0.30, range, 0.36 to 1.58 on 3D-T1WI) was significantly higher than that of the non-injected side (0.52 +/- 0.14, range, 0.30 to 0.76 on 3D-FLAIR; 0.49 +/- 0.11, range, 0.30 to 0.71 on 3D-T1WI) on 3D-FLAIR and 3D-T1WI (P < 0.001), although no significant difference was observed on 3D-CISS (10.03 +/- 2.19, range, 5.19 to 14.98, on the injected side; 9.52 +/- 1.63 range, 7.48 to 13.48, on the non-injected side) (P = 0.11). The mean contrast value on 3D-FLAIR (5.93 +/- 2.57, range, 1.22 to 11.05) was significantly higher than that on 3D-T1WI (1.73 +/- 0.60, range, 0.98 to 3.09) (P < 0.001). Conclusion: The 3D-FLAIR sequence is the most sensitive for observing alteration in inner ear fluid signal after intratympanic gadolinium injection. Our results warrant use of 3D-FLAIR as a sensitive imaging technique to clarify the pathological and morphological mechanisms of disorders of the inner ear.