Three-dimensional Heavily T2-weighted imaging of inner ear and Internal Auditory Canal at 3-T versus 5-T: A...

Inner ear is characterized by fine and intricate anatomy. Due to magnetic inhomogeneity, inner ear imaging has not benefited much from ultra-high field-strength MRI. 5-T may provide an alternative for inner ear imaging. This study aimed to compare image quality and visibility of specific structures between 5-T and 3-T MRI.

Consecutive healthy volunteers who underwent heavily T2-weighted imaging at 3-T and 5-T within one week were prospectively enrolled between September and October 2025. Image quality was rated using Likert scale for overall image, specific inner ear and nerve apparatus. Signal-to-noise ratio, contrast-to-noise ratio and image sharpness were quantitated. Wilcoxon signed-rank tests or paired t tests were used for inter-field comparison. Inter-observer and inter-field agreements were assessed.

A total of 22 participants (median age: 40.50[30.00-49.00] years; 10 females; 44 ears) were included. There was no significant difference of overall image quality between 5-T and 3-T across three readers (average median scores: both 4.67; P> 0.999). Compared with 3-T, 5-T demonstrated a superior visibility for posterior ampullary nerve, superior vestibular nerve, cochlear nerve and cochlear aperture segment of cochlear nerve, as well as foramen singular and osseous spiral lamina. The visibility score of inferior vestibular nerve was marginally higher at 5-T than that at 3-T for readers (P=0.054-0.094). No differences of visualizing evaluated membranous labyrinth structures between two field strengths were observed. Signal-to-noise ratio, contrast-to-noise ratio and image sharpness were higher at 5-T than at 3-T.

Compared with 3-T, three-dimensional heavily T2-weighted sequence at 5-T improved the detectability of nerves significantly, particularly segments coursing through bony ducts, as well as the foramen singular and osseous spiral lamina.