Magnetization Transfer Imaging in Multiple Sclerosis

Magnetization transfer imaging (MTI) has emerged as a vital quantitative MRI technique for probing myelin integrity in multiple sclerosis (MS). By measuring the exchange of magnetization between protons bound to macromolecules (principally myelin) and free water protons, MTI yields metrics such as the magnetization transfer ratio (MTR) and more advanced quantitative magnetization transfer (qMT) parameters—including pool size ratio and exchange rates—that sensitively reflect demyelination and remyelination. In MS lesions, reductions in MTR/qMT correlate with myelin loss, while subtle decreases in normal-appearing white matter (NAWM) often precede lesion formation. Recent technical refinements, notably balanced steady-state free precession (bSSFP)-based acquisitions, have enabled rapid whole-brain mapping of both semi-quantitative and fully quantitative MT metrics within clinically acceptable scan times. When combined with diffusion tensor imaging and other microstructural measures, MTI enhances our capacity to characterise individual lesion evolution, normal tissue changes and therapeutic responses. In clinical trials of remyelinating agents, MTI-derived biomarkers offer objective endpoints, while in routine practice they promise earlier detection of disease activity and improved monitoring of treatment efficacy. Ongoing efforts to harmonise acquisition protocols and multi-centre calibration aim to facilitate widespread adoption, bolster translational research and ultimately guide personalised management strategies in MS.

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Magnetization Transfer Imaging in Multiple Sclerosis publication trend

The graph below shows the total number of articles in magnetization transfer imaging in multiple sclerosis across all publications each year (not limited to Nature Index journals).

Technical terms

Magnetization Transfer Imaging (MTI): An MRI method assessing exchange of magnetization between free water and macromolecular protons, sensitive to myelin content.

Magnetization Transfer Ratio (MTR): A semi-quantitative index of macromolecular proton exchange, used as a proxy for myelin integrity.

Quantitative Magnetization Transfer (qMT): A family of models estimating parameters (pool size ratio, exchange rate) that more directly reflect macromolecular composition.

Pool Size Ratio: The proportion of bound macromolecular protons relative to free water protons, indicative of myelin density.

Inhomogeneous Magnetization Transfer (ihMT): An MT variant optimised for selective sensitivity to myelin without confounding from other macromolecules.

Normal-Appearing White Matter (NAWM): Brain white matter that appears unremarkable on conventional MRI but may harbour microscopic pathology detectable by advanced techniques.

References

1. Longitudinal analysis of new multiple sclerosis lesions with magnetization transfer and diffusion tensor imaging. European Radiology (2023).
2. Watershed regions are more susceptible to tissue microstructural injury in multiple sclerosis. Brain Communications (2024).
3. Inhomogeneous magnetization transfer (ihMT) imaging reveals variable recovery profiles of active MS lesions according to size and localization. Imaging Neuroscience (2024).