Magnetic susceptibility as a B0 field strength independent MRI biomarker of liver iron overload. Issue 3 (25th June 2013)

• Record Type: Journal Article
• Authors: Hernando, Diego; Cook, Rachel J.; Diamond, Carol; Reeder, Scott B.
• Is Part Of: Magnetic resonance in medicine. Volume 70:Issue 3(2013:Sep.)
• Page Start: 648
• Page End: 656
• Publication Date: 2013-06-25
• Subjects: Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.24848
• Languages: English
• ISSNs: 0740-3194

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="mrm24848-sec-0001" sec-type="section"> <title>Purpose</title> <p>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 <italic>B</italic><sub>0</sub> field. The purpose of this work is to demonstrate feasibility of susceptibility‐based LIC quantification using a fat‐referenced approach.</p> </sec> <sec id="mrm24848-sec-0002" sec-type="section"> <title>Methods</title> <p>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, <italic>B</italic><sub>0</sub>‐ and R2*‐mapping. Phantom iron concentration (mg Fe L<sup>−1</sup>) was estimated from <italic>B</italic><sub>0</sub> differences (Δ<italic>B</italic><sub>0</sub>) between vials and neighboring oil. Liver susceptibility and LIC (mg Fe g<sup>−1</sup> dry tissue) was estimated from Δ<italic>B</italic><sub>0</sub> between the lateral right lobe of the liver and adjacent subcutaneous adipose tissue.</p> </sec> <sec id="mrm24848-sec-0003" sec-type="section"> <title>Results</title> <p>Estimated phantom iron concentrations had good correlation with true iron concentrations (1.5 T:slope = 0.86, intercept = 0.72, <italic>r</italic><sup>2</sup> = 0.98; 3 T:slope = 0.85, intercept = 1.73, <italic>r</italic><sup>2</sup> = 0.98). In liver, Δ<italic>B</italic><sub>0</sub> correlated strongly with R2* (1.5 T:<italic>r</italic><sup>2</sup> = 0.86; 3 T:<italic>r</italic><sup>2</sup> = 0.93) and <italic>B</italic><sub>0</sub>‐LIC had good agreement with Ferriscan‐LIC (slopes/intercepts nearly 1.0/0.0, 1.5 T:<italic>r</italic><sup>2</sup> = 0.67, slope = 0.93 ± 0.13, <italic>P</italic> ≈ 0.50, intercept = 1.93 ± 0.78, <italic>P</italic> ≈ 0.02; 3 T:<italic>r</italic><sup>2</sup> = 0.84, slope = 1.01 ± 0.09, <italic>P</italic> ≈ 0.90, intercept = 0.23 ± 0.52, <italic>P</italic> ≈ 0.68).</p> </sec> <sec id="mrm24848-sec-0004" sec-type="section"> <title>Discussion</title> <p>Fat‐referenced, susceptibility‐based LIC estimation is feasible at both field strengths. This approach may enable improved susceptibility mapping in the abdomen. <bold>Magn Reson Med 70:648–656, 2013. © 2013 Wiley Periodicals, Inc</bold>.</p> </sec> </abstract>