Assessing optic nerve integrity in optic neuritis with conventional magnetic resonance imaging

BACKGROUND AND PURPOSE: The aim of this study was to investigate the integrity of the optic nerve using the ratio between T1WI and T2WI (T1/T2) MRI signal intensities, and to assess whether inter-eye differences could indicate the presence of lesions in the optic nerve. MATERIAL AND METHODS: The cohort included eighteen healthy controls and forty-nine individuals with multiple sclerosis; from those, thirty-two had a previous episode of optic neuritis. A method was trained to generate automatic segmentations of the optic nerve. Provided masks were then applied to the T1/T2 map and the mean profile was extracted. Inter-eye asymmetry was calculated from the area under the profiles. The presence of optic nerve lesions was confirmed using double inversion recovery MRI. Group differences were evaluated with non-parametric statistical tests, and the ability of inter-eye asymmetry to identify lesions was assessed using logistic regression. RESULTS: Automated masks showed a moderate agreement with the reference segmentations (mean Dice coefficient ± SD = 0.53 ± 0.12). Eyes with a visible lesion on MRI showed a significantly lower T1/T2 (mean ± SD = 0.61 ± 0.09) compared to other groups (multiple sclerosis without optic neuritis 0.74 ± 0.06, p<0.001; and healthy subjects 0.77 ± 0.09, p<0.001). Inter-eye asymmetry demonstrated a good discriminative performance, with an area under the curve of 0.83, a sensitivity of 0.74, and a specificity of 0.82. CONCLUSION: The findings indicate that conventional MRI can provide clinically meaningful information regarding optic nerve integrity and support the development of automated tools for detecting optic nerve lesions.