An MR fingerprinting approach for quantitative inhomogeneous magnetization transfer imaging

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biomedical Engineering
• Neuroimaging

Background:

• Magnetization transfer (MT) and inhomogeneous MT (ihMT) are crucial MRI contrasts for assessing macromolecular content.
• ihMT is particularly sensitive to myelinated tissue, offering specificity in imaging.
• Current methods require separate acquisitions, limiting efficiency.

Purpose of the Study:

• To develop a single-acquisition technique for characterizing both MT and ihMT properties.
• To generate semiquantitative contrast ratios and quantitative parameter maps simultaneously.
• To improve the efficiency and specificity of macromolecular tissue imaging.

Main Methods:

• A cyclic steady-state approach using multiband and single-band radiofrequency (RF) pulses was employed.
• This technique leverages MT effects to create signal fluctuations, akin to MR fingerprinting.
• Dictionary-based low-rank inversion was used for image reconstruction and parameter estimation.

Main Results:

• Phantom and in vivo brain data at 1.5 Tesla validated the technique.
• ihMT ratio maps demonstrated contrast specific to white matter, aligning with prior research.
• Quantitative estimates of semisolid fraction and dipolar T1 were consistent with literature values.

Conclusions:

• A novel MT-mediated fingerprinting method was successfully demonstrated.
• The approach enables simultaneous generation of semiquantitative MT/ihMT maps and quantitative parameter estimates.
• This technique offers a more efficient way to probe macromolecular tissue characteristics in MRI.