Quantitative MR susceptibility mapping using piece-wise constant regularized inversion of the magnetic field

Area of Science:

• Physics
• Biophysics
• Materials Science

Background:

• Magnetic properties like susceptibility and chemical shift influence the local magnetic field experienced by spins.
• Accurate quantification of these properties is crucial for various scientific and medical applications.
• The inversion problem of determining magnetic properties from magnetic field data is challenging.

Purpose of the Study:

• To develop and validate a Magnetic Resonance Imaging (MRI) based method for accurate quantification of magnetic susceptibility and chemical shift.
• To address the challenging inversion problem of deriving magnetic properties from measured magnetic fields.

Main Methods:

• A piece-wise constant solution was employed using MRI data to solve the inversion problem.
• Magnetic field shifts were estimated from MR phase images.
• MR magnitude images were segmented into regions of uniform magnetic properties, followed by linear regression for susceptibility quantification.

Main Results:

• The developed technique accurately quantified magnetic susceptibility with a precision better than 0.1 ppm over a 10 ppm range.
• Experimental validation was performed on diverse samples including water, vegetable oil, air, Gadolinium, and superparamagnetic iron oxides.
• In vivo feasibility was demonstrated on the human forearm, yielding susceptibility and chemical shift values for soft tissue, cortical bone, and bone marrow consistent with literature.

Conclusions:

• The developed MRI method provides accurate and precise quantification of magnetic susceptibility and chemical shift.
• This technique is robust, validated across various materials, and shows in vivo applicability.
• The findings have significant implications for magnetic property characterization in both research and clinical settings.