Magnetic susceptibility anisotropy outside the central nervous system

Area of Science:

• Medical Imaging
• Biophysics
• Biomolecular Engineering

Background:

• Magnetic susceptibility-based MRI is crucial for characterizing tissue microstructure, chemical composition, and organ function.
• Anisotropic magnetic susceptibility properties and distinct cellular organizations exist in organs like the kidney, heart, and connective tissues, differing from brain myelin.
• Epithelial lipid orientation (kidney), myofilament proteins (heart), and collagen fibrils (knee cartilage) contribute to tissue anisotropy.

Purpose of the Study:

• To review experimental findings on susceptibility anisotropy in the body.
• To explore the underlying mechanisms of tissue susceptibility anisotropy.
• To discuss associated Magnetic Resonance Imaging (MRI) methodologies for quantifying these properties.

Main Methods:

• Quantitative susceptibility mapping (QSM) and susceptibility tensor imaging (STI) are employed to quantify magnetic susceptibility properties.
• Diffusion tensor imaging (DTI) is used to determine tubular and filament directions for QSM measurements.
• These MRI techniques provide complementary information to traditional methods.

Main Results:

• STI can track tubules across all kidney layers (cortex, outer medulla, inner medulla).
• STI detected myofibers throughout the myocardium in the heart.
• QSM in knee cartilage revealed three distinct layers by leveraging collagen's anisotropic susceptibility features.

Conclusions:

• QSM and STI are promising tools for studying tissue susceptibility and anisotropy.
• These techniques offer valuable insights into tissue microstructure and function in various organs.
• Overcoming technical challenges is necessary for the routine clinical application of QSM and STI.