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Multiple sclerosis: magnetization transfer MR imaging of white matter before lesion appearance on T2-weighted images
G B Pike1, N De Stefano, S Narayanan
1McConnell Brain Imaging Center, Montreal Neurological Institute, 3801 University St, Montreal, Québec, Canada. bruce@bic.mni.mcgill.ca
Purpose:
To determine the evolution of magnetization transfer (MT) in white matter regions before and after plaque development in patients with multiple sclerosis (MS).
Materials And Methods:
In a 5-year longitudinal evaluation, 30 patients with MS underwent conventional magnetic resonance (MR) imaging, MT MR imaging, and clinical assessment. Cross-sectional data in 12 healthy subjects were also collected. Semiautomated lesion classification with use of T2-weighted MR images was used to measure the time course of the MT ratio (calculated with MR data acquired without and with MT saturation) in every voxel and to help analyze the relationship with the status of lesions depicted on T2-weighted images.
Results:
There was a significant (P <.001) temporal decline in lesion MT ratio after lesion appearance on T2-weighted images. A significant (P <. 001) progressive decline in MT ratio was also present in voxels that later became lesions, prior to initial detection on T2-weighted images. Even 1(1/2) years prior to lesion appearance, the MT ratio (33.3%) in regions destined to become such lesions was significantly (P <.001) lower than that in both white matter in healthy subjects (41.3%) and other normal-appearing white matter in patients with MS (38.1%).
Conclusion:
The MT ratio reveals progressive focal abnormalities in MS that antedate by up to 2 years the appearance of lesions on T2-weighted MR images.
Insights
Magnetization transfer ratio (MT ratio) changes in multiple sclerosis (MS) white matter reveal abnormalities up to two years before lesions appear on MRI scans. This early detection of focal abnormalities in MS could improve patient outcomes.
Area of Science:
- Neuroimaging
- Neurology
- Medical Physics
Background:
- Multiple sclerosis (MS) is a chronic neurological disease characterized by demyelination and axonal damage.
- White matter lesions are a hallmark of MS, but their development and progression are not fully understood.
- Magnetization transfer (MT) imaging is a sensitive MRI technique that can probe microstructural changes in white matter.
Purpose of the Study:
- To investigate the longitudinal changes in the MT ratio in white matter regions of patients with MS.
- To determine if MT ratio alterations precede the appearance of lesions on conventional MRI.
- To correlate MT ratio changes with lesion development and progression over time.
Main Methods:
- A 5-year longitudinal study involving 30 MS patients and 12 healthy controls.
- Conventional MRI, MT MRI, and clinical assessments were performed.
- Semiautomated lesion classification and voxel-wise analysis of MT ratio were used to track changes relative to T2-weighted lesion status.
Main Results:
- A significant temporal decline in MT ratio was observed in MS lesions after their appearance.
- A progressive decline in MT ratio was detected in voxels that later developed into lesions, preceding their detection on T2-weighted images.
- Regions that eventually became lesions showed significantly lower MT ratios up to 1.5 years before lesion appearance compared to healthy controls and normal-appearing white matter in MS patients.
Conclusions:
- The MT ratio is a sensitive marker for detecting early, focal white matter abnormalities in MS.
- MT imaging can identify pathological changes in MS white matter up to two years before lesions are visible on conventional MRI.
- These findings suggest MT ratio changes reflect an early stage of MS pathology, potentially offering a window for earlier intervention.