title: Assessment of liver fibrosis using fast strain-encoded MRI driven by inherent cardiac motion.
abstract: OBJECTIVE
  An external driver-free MRI method for assessment of liver fibrosis offers a promising noninvasive tool for diagnosis and monitoring of liver disease. Lately, the heart's intrinsic motion and MR tagging have been utilized for the quantification of liver strain. However, MR tagging requires multiple breath-hold acquisitions and substantial postprocessing. In this study, we propose the use of a fast strain-encoded (FSENC) MRI method to measure the peak strain (Sp) in the liver's left lobe, which is in close proximity and caudal to the heart. Additionally, we introduce a new method of measuring heart-induced shear wave velocity (SWV) inside the liver.
  
  
  METHODS
  Phantom and in vivo experiments (11 healthy subjects and 11 patients with liver fibrosis) were conducted. Reproducibility experiments were performed in seven healthy subjects.
  
  
  RESULTS
  Peak liver strain, Sp, decreased significantly in fibrotic liver compared with healthy liver (6.46% ± 2.27% vs 12.49% ± 1.76%; P < 0.05). Heart-induced SWV increased significantly in patients compared with healthy subjects (0.15 ± 0.04 m/s vs 0.63 ± 0.32 m/s; P < 0.05). Reproducibility analysis yielded no significant difference in Sp (P = 0.47) or SWV (P = 0.56).
  
  
  CONCLUSIONS
  Accelerated external driver-free noninvasive assessment of left liver lobe strain and SWV is feasible using strain-encoded MRI. The two measures significantly separate healthy subjects from patients with fibrotic liver. Magn Reson Med 74:106-114, 2015. © 2014 Wiley Periodicals, Inc.
authors.affiliation: Imaging Sciences Training Program, The National Institute of Biomedical Imaging and Bioengineering, The National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Harouni
authors.affiliation: Biomedical and Metabolic Imaging Branch, The National Institute of Diabetes and Digestive and Kidney Diseases, The National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Gharib
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Sciences, Division of MR Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Nael F
authors.initials: NF
authors.lastname: Osman
authors.affiliation: Critical Care Medicine Department, Clinical Research Center, The National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Caryn
authors.initials: C
authors.lastname: Morse
authors.affiliation: Liver Diseases Branch, The National Institute of Diabetes and Digestive and Kidney Diseases, The National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Theo
authors.initials: T
authors.lastname: Heller
authors.affiliation: Biomedical and Metabolic Imaging Branch, The National Institute of Diabetes and Digestive and Kidney Diseases, The National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Khaled Z
authors.initials: KZ
authors.lastname: Abd-Elmoniem
keywords: SENC; fibrosis; liver motion; liver stiffness; strain-encoded MRI
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