Authors
Anna Lundberg, Ronnie Wirestam, Jimmy Lätt, Linda Knutsson, Emelie Lind
Published in
Magma (New York, N.Y.). Aug 06, 2026. Epub Aug 06, 2026.
Abstract
Quantitative susceptibility mapping (QSM) is a semi-quantitative method, i.e., only differences in magnetic susceptibility can be quantified. The lack of a stable internal reference hampers longitudinal and systematic comparisons among subjects. In this study, a phase-based approach, enabling the use of an external reference, is proposed.
By modeling the object geometry and analyzing the object-induced magnetic field distortion in the external reference, a relationship between the manifested phase and susceptibility was established. The proposed theoretical framework was validated using a numerical head phantom and 3 T MRI measurements, investigating five phantoms with different concentrations of gadolinium and one healthy volunteer. The derived theoretical relationship, together with accurate phase measurements, provided the absolute mean magnetic susceptibility of the object of interest.
Excellent accuracy was demonstrated in the numerical head phantom. Encouraging, although somewhat underestimated, susceptibility results were obtained for the MRI phantom measurements. The relationship between measured and theoretical susceptibility values showed excellent correlation (r = 0.98, p = 0.004). The in vivo measurement yielded an absolute mean susceptibility of 0.02 ppm (relative to water).
Feasibility and proof of concept were demonstrated, and the approach, in combination with conventional QSM, offers an alternative reference solution with potential to facilitate absolute QSM maps.
PMID:
42560478
Bibliographic data and abstract were imported from PubMed on 06 Aug 2026.
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