Fast bound pool fraction mapping via steady-state magnetization transfer saturation using single-shot EPI

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Quantitative magnetization transfer (qMT) imaging is crucial for assessing brain tissue properties.
• Mapping fundamental parameters like bound pool fraction (BPF) is essential for clinical qMT applications.
• Current qMT methods can be time-consuming, limiting their clinical utility.

Purpose of the Study:

• To develop and validate a fast MRI method for mapping the bound pool fraction (BPF) in the human brain.
• To enable clinical applications of qMT imaging through reduced acquisition times.
• To provide accurate BPF measurements for potential diagnostic use.

Main Methods:

• Utilized steady-state MT theory in the fast-exchange approximation.
• Developed a 10-minute echo planar imaging-based MRI protocol for BPF mapping.
• Included inversion recovery T1 mapping and B1 error mapping within the protocol.
• Validated the method in healthy subjects and a multiple sclerosis patient against a reference qMT acquisition.

Main Results:

• BPF measurements in white and gray matter align with established literature values.
• The developed method demonstrated a median voxel-wise percentage error of 4.6% compared to the reference.
• Linear regression showed strong agreement (slope 0.83) between new and reference BPF measurements.
• BPF changes were observed in MS lesions, indicating sensitivity to pathology.

Conclusions:

• The developed method provides accurate BPF estimates with significantly reduced scan time.
• This myelin-sensitive measurement technique shows promise for broader clinical adoption.
• The fast qMT mapping approach facilitates bringing advanced neuroimaging closer to clinical practice.