White and Gray Matter Multiple Sclerosis Spinal Cord Lesion Characteristics and Individualized Tissue Damage...

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging (MRI)
• Neurology

Background:

• Multiple sclerosis (MS) involves spinal cord (SC) damage, affecting both white matter (WM) and gray matter (GM).
• Accurate characterization of SC tissue damage, including diffuse injury, is crucial for understanding MS progression and treatment efficacy.
• Current imaging techniques may have limitations in fully assessing subregional SC microstructural integrity in MS.

Purpose of the Study:

• To demonstrate the utility of 7 Tesla (7T) MP2RAGE T1 mapping for evaluating SC tissue damage and lesion characteristics in MS.
• To assess SC damage at both subregional and individual levels using quantitative T1 values.
• To explore the potential of this technique for characterizing focal and diffuse WM/GM SC tissue injury in relapsing-remitting MS (pwRRMS).

Main Methods:

• Fifteen pwRRMS and 15 healthy controls (HC) underwent 7T cervical 3D MP2RAGE imaging.
• Automatic SC and lesion segmentations were performed, followed by manual correction.
• T1 values were extracted from specific ROIs (WM tracts and GM subregions) and registered to a template space.
• Individual Z-score maps and patient-specific barplots were computed to quantify tissue impairment.
• MS lesions were characterized by relative lesion load (RLL%), frequency maps, and topography.

Main Results:

• Lesions were primarily in the posterior SC, with GM showing the highest RLL.
• A significant gradient in T1 values was observed: T1_HC < T1_NAT < T1_lesion.
• Elevated T1 values in normal-appearing tissues (NATs) of lesion-free patients suggest diffuse microstructural injury.
• Z-score barplots revealed abnormal SC voxels in over 10% of pwRRMS, demonstrating individualized tissue damage visualization.
• Mixed GM-WM lesions had higher T1 values and larger volumes than WM-only lesions.

Conclusions:

• 7T MP2RAGE T1 mapping is a sensitive tool for characterizing focal and diffuse SC tissue damage in MS.
• Combined with Z-score metrics, it provides a quantitative, individualized framework for assessing SC tissue integrity.
• This approach holds potential for grading microstructural impairment and monitoring neuroprotective treatment effects in MS.