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Magnetic susceptibility as a B 0 field strength independent MRI biomarker of liver iron overload
Author(s) -
Hernando Diego,
Cook Rachel J.,
Diamond Carol,
Reeder Scott B.
Publication year - 2013
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.24848
Subject(s) - imaging phantom , quantitative susceptibility mapping , magnetic susceptibility , chemistry , nuclear medicine , liver tissue , nuclear magnetic resonance , magnetic resonance imaging , materials science , medicine , crystallography , radiology , physics
Purpose MR‐based quantification of liver magnetic susceptibility may enable field strength‐independent measurement of liver iron concentration (LIC). However, susceptibility quantification is challenging, due to nonlocal effects of susceptibility on the B 0 field. The purpose of this work is to demonstrate feasibility of susceptibility‐based LIC quantification using a fat‐referenced approach. Methods Phantoms consisting of vials with increasing iron concentrations immersed between oil/water layers, and 27 subjects (9 controls/18 subjects with liver iron overload) were scanned. Ferriscan (1.5 T) provided R2‐based reference LIC. Multiecho three‐dimensional‐SPGR (1.5 T/3 T) enabled fat‐water, B 0 ‐ and R2*‐mapping. Phantom iron concentration (mg Fe L −1 ) was estimated from B 0 differences (Δ B 0 ) between vials and neighboring oil. Liver susceptibility and LIC (mg Fe g −1 dry tissue) was estimated from Δ B 0 between the lateral right lobe of the liver and adjacent subcutaneous adipose tissue. Results Estimated phantom iron concentrations had good correlation with true iron concentrations (1.5 T:slope = 0.86, intercept = 0.72, r 2 = 0.98; 3 T:slope = 0.85, intercept = 1.73, r 2 = 0.98). In liver, Δ B 0 correlated strongly with R2* (1.5 T: r 2 = 0.86; 3 T: r 2 = 0.93) and B 0 ‐LIC had good agreement with Ferriscan‐LIC (slopes/intercepts nearly 1.0/0.0, 1.5 T: r 2 = 0.67, slope = 0.93 ± 0.13, P ≈ 0.50, intercept = 1.93 ± 0.78, P ≈ 0.02; 3 T: r 2 = 0.84, slope = 1.01 ± 0.09, P ≈ 0.90, intercept = 0.23 ± 0.52, P ≈ 0.68). Discussion Fat‐referenced, susceptibility‐based LIC estimation is feasible at both field strengths. This approach may enable improved susceptibility mapping in the abdomen. Magn Reson Med 70:648–656, 2013. © 2013 Wiley Periodicals, Inc .