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Quantitative susceptibility mapping (QSM) minimizes interference from cellular pathology in R2* estimation of liver iron concentration
Author(s) -
Li Jianqi,
Lin Huimin,
Liu Tian,
Zhang Zhuwei,
Prince Martin R.,
Gillen Kelly,
Yan Xu,
Song Qi,
Hua Ting,
Zhao Xiance,
Zhang Miao,
Zhao Yu,
Li Gaiying,
Tang Guangyu,
Yang Guang,
Brittenham Gary M.,
Wang Yi
Publication year - 2018
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.26019
Subject(s) - quantitative susceptibility mapping , fibrosis , gradient echo , medicine , pathological , magnetic resonance imaging , pathology , nuclear medicine , radiology
Background A challenge for R2 and R2* methods in measuring liver iron concentration (LIC) is that fibrosis, fat, and other hepatic cellular pathology contribute to R2 and R2* and interfere with LIC estimation. Purpose To examine the interfering effects of fibrosis, fat, and other lesions on R2* LIC estimation and to use quantitative susceptibility mapping (QSM) to reduce these distortions. Study Type Prospective. Phantoms, Subjects Water phantoms with various concentrations of gadolinium (Gd), collagen (Cl, modeling fibrosis), and fat; nine healthy controls with no known hepatic disease, nine patients with known or suspected hepatic iron overload, and nine patients with focal liver lesions. Field Strength/Sequence The phantoms and human subjects were imaged using a 3D multiecho gradient‐echo on clinical 1.5T and 3T MRI systems. Assessment QSM and R2* images were postprocessed from the same gradient‐echo data. Fat contributions to susceptibility and R2* were corrected in signal models for LIC estimation. Statistical Tests Polynomial regression analyses were performed to examine relations among susceptibility, R2* and true [Gd] and [Cl] in phantoms, and among susceptibility and R2* in patient livers. Results In phantoms, R2* had a strong nonlinear dependency on [Cl], [fat], and [Gd], while susceptibility was linearly dependent (R 2 > 0.98). In patients, R2* was highly sensitive to liver pathological changes, including fat, fibrosis, and tumors, while QSM was relatively insensitive to these abnormalities ( P = 0.015). With moderate iron overload, liver susceptibility and R2* were not linearly correlated over a common R2* range [0, 100] sec −1 ( P = 0.35). Data Conclusion R2* estimation of LIC is prone to substantial nonlinear interference from fat, fibrosis, and other lesions. QSM processing of the same gradient echo MRI data can effectively minimize the effects of cellular pathology. Level of Evidence : 1 Technical Efficacy : Stage 1 J. Magn. Reson. Imaging 2018;48:1069–1079.