Effect of the Surrounding Magnetic Environment of Temporal Bone on the Fluid Signal Intensity in Human Inner Ear Using a Combined T2 Preparation Pulse and Fluid Attenuated Inversion Pulse Technique.

Purpose: Recently, the utility of non-contrast MR endolymphatic hydrops imaging was reported, but the pitfall was indicated based on T2 preparation pulse sensitiveness to local static magnetic field (B0) inhomogeneity. The purpose of this study is to clarify the effects of surrounding magnetic environment of temporal bone to lymphatic fluid signal intensity on the T2 preparation and fluid attenuated inversion recovery pulse combination (T2prep 3D-FLAIR) technique in human inner ear study.

Methods: We prepared a custom-made phantom comprising a chicken leg bone submersed in saline. To evaluate signal characteristics of saline close to bone, multiple TE gradient echoes, T2 relaxation time measurement, and T2prep 3D-FLAIR image were acquired. In the vicinity of the vestibule of a healthy volunteer, similar examinations were executed. Additionally, to investigate the influence of the magnetic environment from B0, the evaluation was performed in five head position settings relative to B0.

Results: In both the phantom case and volunteer case, together with T2 star signal intensity attenuation, T2 relaxation time shortening was observed on fluid around bone. Specifically, at the outer edge in the vestibule and cochlea of the volunteer, T2 relaxation time was shorter than that of center of vestibule and that of cochlea. In the T2prep 3D-FLAIR image, higher signal intensity was observed at the same location on the outer edge of them. These results showed that bone affects surrounding fluid magnetic environment. Also, for B0 influence, despite a large area variation ratio, there is no statistically significant difference correlated to orientation within B0.

Conclusion: The surrounding magnetic environment of the temporal bone affects lymphatic fluid signals of the peripheral part of the human inner ear on T2prep 3D-FLAIR technique.