Chronic multiple sclerosis lesions: characterization with high-field-strength MR imaging

Area of Science:

• Neuroimaging
• Pathology
• Magnetic Resonance Imaging

Background:

• Multiple sclerosis (MS) is a demyelinating disease affecting the central nervous system.
• Understanding the MR imaging contrast mechanisms in MS lesions is crucial for accurate diagnosis and monitoring.
• Susceptibility-weighted imaging (SWI) offers insights into tissue magnetic properties, potentially related to iron and myelin content.

Purpose of the Study:

• To investigate the mechanism of MR imaging contrast in MS lesions using SWI.
• To correlate MR imaging findings with histologic evidence of iron and myelin.
• To assess the role of iron and myelin in generating MS lesion contrast.

Main Methods:

• High-spatial-resolution 7.0-T SWI was performed on 21 patients with MS.
• Quantitative phase and R2* images were analyzed in 220 chronic MS lesions.
• Postmortem MR imaging at 7.0 T and 11.7 T was correlated with immunohistochemical staining for myelin, iron, and ferritin.

Main Results:

• Most lesions (60.5%) showed normal phase and reduced R2*, indicating severe myelin and iron loss.
• A significant portion of lesions (38.2%) exhibited negative phase shift and varied R2* appearance, correlating with focal iron deposits and myelin loss.
• Postmortem studies confirmed these lesion contrast patterns and their association with specific histologic features.

Conclusions:

• Combined analysis of 7.0-T R2* and phase data can characterize MS lesion pathology.
• Decreased R2* values suggest profound myelin loss in MS lesions.
• Negative phase shifts in MS lesions are indicative of focal iron accumulation.