Long T2 water in multiple sclerosis: what else can we learn from multi-echo T2 relaxation?

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging (MRI)
• Multiple Sclerosis (MS) Research

Background:

• Multi-echo T(2) measurements are crucial for understanding brain pathology in multiple sclerosis (MS).
• The T(2) distribution can reveal additional water reservoirs linked to inflammation or edema beyond myelin and total water content.
• Characterizing longer T(2) components in MS lesions and normal-appearing white matter (NAWM) is essential for a comprehensive understanding.

Purpose of the Study:

• To better define the T(2) distribution in MS lesions and NAWM.
• To specifically characterize the longer T(2) components within these regions.
• To investigate the relationship between these T(2) characteristics and clinical/imaging parameters.

Main Methods:

• Acquisition of magnetisation transfer (MT), T(1), and 48-echo T(2) relaxation data from 20 MS subjects.
• Defining regions of interest (ROIs) in both MS lesions and NAWM.
• Analysis of T(2) distribution, geometric mean T(2) (GMT(2)), water content (WC), T(1), magnetisation transfer ratio (MTR), and myelin water fraction (MWF).

Main Results:

• Twenty-seven out of 107 lesions exhibited a markedly prolonged T(2) signal (200-800 ms).
• Lesions with a Long-T(2) signal showed higher GMT(2), WC, and T(1), with reduced MTR and myelin water fraction (MWF) compared to other lesions.
• Subjects with Long-T(2) lesions had significantly longer disease duration; strong correlations found between T(1) and Long-T(2) fraction.

Conclusions:

• A potential source of the Long-T(2) signal in MS lesions is increased extracellular water.
• This study underscores the utility of extending the data acquisition window in multi-echo T(2) relaxation sequences for improved MS characterization.
• Longer T(2) components provide valuable insights into MS pathology and disease progression.