Premium
Assessment of MR‐based R 2 * and quantitative susceptibility mapping for the quantification of liver iron concentration in a mouse model at 7T
Author(s) -
Simchick Gregory,
Liu Zhi,
Nagy Tamas,
Xiong May,
Zhao Qun
Publication year - 2018
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.27173
Subject(s) - quantitative susceptibility mapping , magnetic susceptibility , chemistry , nuclear magnetic resonance , ferritin , analytical chemistry (journal) , magnetic resonance imaging , chromatography , medicine , physics , crystallography , biochemistry , radiology
Purpose To assess the feasibility of quantifying liver iron concentration (LIC) usingR 2 *and quantitative susceptibility mapping (QSM) at a high field strength of 7 Tesla (T). Methods Five different concentrations of Fe‐dextran were injected into 12 mice to produce various degrees of liver iron overload. After mice were sacrificed, blood and liver samples were harvested. Ferritin enzyme‐linked immunosorbent assay (ELISA) and inductively coupled plasma mass spectrometry were performed to quantify serum ferritin concentration and LIC. Multiecho gradient echo MRI was conducted to estimateR 2 *and the magnetic susceptibility of each liver sample through complex nonlinear least squares fitting and a morphology enabled dipole inversion method, respectively. Results Average estimates of serum ferritin concentration, LIC,R 2 * , and susceptibility all show good linear correlations with injected Fe‐dextran concentration; however, the standard deviations in the estimates ofR 2 *and susceptibility increase with injected Fe‐dextran concentration. BothR 2 *and susceptibility measurements also show good linear correlations with LIC (R 2 = 0.78 and R 2 = 0.91, respectively), and a susceptibility‐to‐LIC conversion factor of 0.829 ppm/(mg/g wet) is derived. Conclusion The feasibility of quantifying LIC using MR‐based R 2 *and QSM at a high field strength of 7T is demonstrated. Susceptibility quantification, which is an intrinsic property of tissues and benefits from being field‐strength independent, is more robust thanR 2 *quantification in this ex vivo study. A susceptibility‐to‐LIC conversion factor is presented that agrees relatively well with previously published QSM derived results obtained at 1.5T and 3T.