Magnetic susceptibility as a B0 field strength independent MRI biomarker of liver iron overload
Version of Record online: 25 JUN 2013
Copyright © 2013 Wiley Periodicals, Inc.
Magnetic Resonance in Medicine
Volume 70, Issue 3, pages 648–656, September 2013
How to Cite
Hernando, D., Cook, R. J., Diamond, C. and Reeder, S. B. (2013), Magnetic susceptibility as a B0 field strength independent MRI biomarker of liver iron overload. Magn Reson Med, 70: 648–656. doi: 10.1002/mrm.24848
- Issue online: 27 AUG 2013
- Version of Record online: 25 JUN 2013
- Manuscript Accepted: 28 MAY 2013
- Manuscript Revised: 20 MAY 2013
- Manuscript Received: 4 NOV 2012
- NIH. Grant Numbers: R01 DK083380, R01 DK088925, RC1 EB010384, R01 DK096169
- Wisconsin Alumni Research Foundation (WARF) Accelerator Program
- University of Wisconsin Institute for Clinical and Translational Research (ICTR)
- GE Healthcare
- iron overload;
- chemical shift encoded imaging;
- field map;
- magnetic resonance imaging;
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 B0 field. The purpose of this work is to demonstrate feasibility of susceptibility-based LIC quantification using a fat-referenced approach.
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, B0- and R2*-mapping. Phantom iron concentration (mg Fe L−1) was estimated from B0 differences (ΔB0) between vials and neighboring oil. Liver susceptibility and LIC (mg Fe g−1 dry tissue) was estimated from ΔB0 between the lateral right lobe of the liver and adjacent subcutaneous adipose tissue.
Estimated phantom iron concentrations had good correlation with true iron concentrations (1.5 T:slope = 0.86, intercept = 0.72, r2 = 0.98; 3 T:slope = 0.85, intercept = 1.73, r2 = 0.98). In liver, ΔB0 correlated strongly with R2* (1.5 T:r2 = 0.86; 3 T:r2 = 0.93) and B0-LIC had good agreement with Ferriscan-LIC (slopes/intercepts nearly 1.0/0.0, 1.5 T:r2 = 0.67, slope = 0.93 ± 0.13, P ≈ 0.50, intercept = 1.93 ± 0.78, P ≈ 0.02; 3 T:r2 = 0.84, slope = 1.01 ± 0.09, P ≈ 0.90, intercept = 0.23 ± 0.52, P ≈ 0.68).
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.