3D Heavily T2-Weighted Imaging of Inner Ear and Internal Auditory Canal at 3T vs 5T: A Comparative Study

The 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. 5T may provide an alternative for inner ear imaging. This study aimed to compare image quality and visibility of specific structures between 5T and 3T MRI.

Consecutive healthy volunteers, who underwent heavily T2-weighted imaging at 3T and 5T within 1 week, were prospectively enrolled between September and October 2025. Image quality was rated using the Likert scale for overall image and specifically the inner ear and nerve apparatus. SNR, contrast-to-noise ratio (CNR), and image sharpness were quantitated. Wilcoxon signed-rank tests or paired t tests were used for interfield comparison. Interobserver and interfield agreements were assessed.

A total of 22 participants (median age: 40.50 [30.00-49.00] years; 10 women; 44 ears) were included. There was no observed difference in overall image quality between 5T and 3T across 3 readers (average median scores: both 4.67; P > .999). Compared with 3T, 5T demonstrated a superior visibility for the posterior ampullary nerve, superior vestibular nerve, cochlear nerve (CN), and cochlear aperture segment of CN, as well as foramen singulare and osseous spiral lamina. The visibility score of the inferior vestibular nerve was marginally higher at 5T than that at 3T for readers (P = .054-.094). No differences in visualizing evaluated membranous labyrinth structures between 2 field strengths were observed. SNR, CNR, and image sharpness were higher at 5T than at 3T.

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