Time-efficient, high-resolution, whole brain three-dimensional macromolecular proton fraction mapping.

Area of Science:

• Neuroimaging
• Quantitative MRI
• Biomarker Development

Background:

• Macromolecular proton fraction (MPF) mapping is a quantitative MRI technique used to assess myelination in neural tissues.
• Current MPF mapping methods can be time-consuming and require multiple source images.

Purpose of the Study:

• To develop a high-resolution, whole-brain MPF mapping technique.
• To reduce scan time by minimizing the number of required source images.

Main Methods:

• A synthetic reference image was reconstructed from R1 and proton density maps, replacing an acquired reference image without magnetization transfer (MT) saturation.
• This approach enabled 3D whole-brain MPF mapping with 1.25 mm isotropic resolution and a 20-minute scan time.
• The method was validated in eight healthy subjects against standard MPF mapping.

Main Results:

• MPF values in white and gray matter showed close agreement with acquired reference methods, with minimal bias and low within-subject variability (<2%).
• High-resolution MPF maps revealed sharp white-gray matter contrast and detailed anatomical structures, including iron-rich gray matter regions.
• The technique demonstrated improved resolution and neuroanatomical contrast.

Conclusions:

• The proposed synthetic reference method enhances MPF mapping resolution and accuracy.
• This technique offers unique neuroanatomical contrast features for improved visualization of brain structures.
• It provides a more efficient approach to quantitative MRI-based myelination assessment.