Ultra-high-field 5 T MRI for parotid gland assessment in Sjögren's syndrome: Improved image quality and reliable fat fraction quantification.

BACKGROUND

Ultra-high-field 5 T MRI systems offers potential advantages in signal-to-noise ratio(SNR) for visualizing fine anatomical structures. This prospective study aimed to assess the feasibility of parotid gland imaging in patients with Sjögren's syndrome (SS) at 5 T MRI and to compare image quality and fat fraction (FF) with between 5 T and 3 T MRI.

METHODS

Thirty-one patients with SS underwent MRI examinations on both 3 T and 5 T scanners from October 2024 to August 2025. The sequences included transverse T1-weighted (T1W) sequence, transverse T2-weighted (T2W) fat-only, transverse T2-weighted (T2W) water-only, 3D MR sialography(MRS), and sequences for FF quantification: Iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL-IQ) at 3 T/Fat Analysis & Calculation Technique (FACT3d) at 5 T. Image quality was assessed subjectively using a five-point Likert scale and objectively by calculating signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and the contrast ratio (CR). MRS sialography staging and parotid gland FF measurements were also performed. Statistical comparisons were made using paired t-tests, Wilcoxon signed-rank tests, Bland-Altman analysis, Pearson Correlation analysis and intraclass correlation coefficient (ICC).

RESULTS

Compared with 3 T MRI, 5 T MRI demonstrated significantly superior subjective image quality scores, SNR, and CNR across all anatomical sequences (all p < 0.05), with the most pronounced improvement on T2WI. 5 T MRS showed a tendency to detect more advanced ductal changes and achieved significantly higher ductal CNR (all p < 0.05). FF measurements between 5 T and 3 T showed excellent agreement and a strong positive correlation (r = 0.981, p < 0.01).

CONCLUSIONS

5 T MRI provides markedly improved image quality for parotid gland assessment in SS while maintaining excellent consistency in FF quantification and sialography staging compared with 3 T MRI, highlighting its potential for detecting early-stage glandular changes.