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An external reference to enable quantitative susceptibility mapping (QSM) in absolute terms: theoretical
Anna Lundberg1, Ronnie Wirestam2, Jimmy Lätt3
1Department of Medical Radiation Physics, Lund University, Skåne University Hospital, 22185, Lund, Sweden. anna.lundberg@med.lu.se.
Magma (New York, N.Y.)
|August 6, 2026
Summary
A new phase-based approach provides an external reference for quantitative susceptibility mapping (QSM), enabling absolute magnetic susceptibility measurements. This method overcomes limitations of current QSM techniques for longitudinal studies.
Area of Science:
- Medical Imaging
- Biophysics
- Magnetic Resonance Imaging
Background:
- Quantitative susceptibility mapping (QSM) is semi-quantitative, lacking a stable internal reference for comparisons.
- This limitation hinders longitudinal and multi-subject studies using QSM.
Purpose of the Study:
- To propose a novel phase-based approach for QSM utilizing an external reference.
- To enable the quantification of absolute magnetic susceptibility.
Main Methods:
- A theoretical framework was developed by modeling object geometry and analyzing induced magnetic field distortion.
- Validation was performed using numerical head phantoms, MRI phantoms with varying gadolinium concentrations, and in vivo measurements in a healthy volunteer.
Main Results:
- The method demonstrated excellent accuracy in numerical simulations.
- MRI phantom measurements showed encouraging, though slightly underestimated, susceptibility values with high correlation (r=0.98).
- In vivo measurements yielded an absolute mean susceptibility of 0.02 ppm relative to water.
Conclusions:
- The feasibility and proof of concept for the external reference approach were demonstrated.
- This method offers a potential solution for absolute QSM mapping when combined with conventional QSM techniques.
