Quantitative susceptibility mapping for susceptibility source separation with adaptive relaxometric constant...

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Distinguishing paramagnetic and diamagnetic sources within brain voxels is crucial for understanding tissue composition.
• Existing magnetic susceptibility mapping methods often require multiple orientations or complex data processing.
• Quantitative susceptibility mapping (QSM) is a powerful tool for assessing tissue properties related to iron and myelin.

Purpose of the Study:

• To develop and validate a novel single-orientation quantitative susceptibility mapping method with adaptive relaxometric constant estimation (QSM-ARCS) for accurate magnetic susceptibility source separation.
• To investigate the opposing susceptibilities and their anisotropic effects in the white matter of healthy volunteers.
• To explore the potential of QSM-ARCS-derived susceptibilities as biomarkers for myelin and iron content.

Main Methods:

• Acquisition of multiple spoiled gradient echo and diffusion tensor imaging data from ten healthy volunteers using a 3 T MRI scanner.
• Reconstruction of opposing susceptibility and fractional anisotropy (FA) maps using the proposed QSM-ARCS method.
• Evaluation of QSM-ARCS agreement with a reference susceptibility source separation method (χ-separation) using Bland-Altman analysis and assessment of relationships between susceptibilities and FA.

Main Results:

• QSM-ARCS successfully reconstructed susceptibility maps without significant artifacts.
• QSM-ARCS opposing susceptibility values showed excellent agreement with the χ-separation method.
• Significant correlations were found between FA and both negative (inverse) and positive (proportional) susceptibilities, with distinct fiber orientation dependencies for each.

Conclusions:

• QSM-ARCS accurately estimates opposing magnetic susceptibilities from single-orientation gradient echo data, comparable to established methods.
• The identified relationships between opposing susceptibilities and FA, along with their orientation dependencies, provide valuable insights into white matter microstructure.
• Opposing susceptibilities derived from QSM-ARCS hold promise as direct biomarkers for myelin and iron content, potentially facilitating clinical translation.