Quantitative susceptibility mapping of human brain reflects spatial variation in tissue composition

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Gradient echo MRI phase offers insights into brain tissue composition, including iron and myelin.
• Quantitative phase imaging is crucial for functional brain anatomy and disease diagnosis.
• Limitations of phase imaging include nonlocal and orientation-dependent properties, necessitating reliable magnetic susceptibility quantification.

Purpose of the Study:

• To develop a novel, accurate, and phase-wrap insensitive method for magnetic susceptibility mapping.
• To overcome the limitations of traditional phase imaging for quantitative analysis.
• To enable deeper investigation into brain physiology and pathophysiology.

Main Methods:

• Developed a susceptibility mapping method using two complementary equations: the Fourier relationship between phase and susceptibility, and its spatial frequency domain derivative.
• Employed iterative implementation for high-quality in vivo human brain susceptibility map reconstruction.
• Validated the method through numerical simulations and in vivo imaging.

Main Results:

• The proposed method achieved susceptibility map reconstruction nearly free of streaking artifacts.
• High-quality in vivo human brain susceptibility maps were successfully reconstructed.
• The maps showed excellent contrast for iron-rich deep nuclei and white matter, revealing anisotropic magnetic susceptibility in white matter.

Conclusions:

• The novel susceptibility mapping method provides accurate and phase-wrap insensitive quantification of magnetic susceptibility.
• This technique enhances visualization of brain tissue composition, including iron distribution and white matter architecture.
• The findings suggest potential for improved study of brain physiology, pathophysiology, and white matter micro-architectures.