title: Repeatability of magnetic resonance elastography for quantification of hepatic stiffness.
abstract: OBJECTIVE
  To determine the sources of variability of MRE hepatic stiffness measurements using healthy volunteers and patients and to calculate the minimum change required for statistical significance. Hepatic stiffness measured with magnetic resonance elastography (MRE) has demonstrated tremendous potential as a noninvasive surrogate of hepatic fibrosis, although the underlying repeatability of MRE for longitudinal tracking of liver disease has not been documented.
  
  
  METHODS
  MRE stiffness measurements from 20 healthy volunteers and 10 patients were obtained twice on the same day, and repeated 2-4 weeks later for volunteers in this institutional review board-approved study. A linear mixed effects model was used to estimate the component sources of variability in the data.
  
  
  RESULTS
  The standard deviation of MRE measurements of the same individual on different days is 11.9% (percent of the measured stiffness) using the same reader and 12.0% using different readers. The standard deviation of the difference between two measurements (i.e., longitudinal change in an individual) is 17.4%; the corresponding 95% confidence interval for zero change is (-27.0%, 37.0%).
  
  
  CONCLUSIONS
  MRE is a repeatable method for quantifying liver stiffness. Using the described MRE technique, changes greater than 37.0% of the smaller measured stiffness value represent meaningful changes in longitudinal liver stiffness measurements.
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin 53792-3252, USA.
authors.forename: Catherine D G
authors.initials: CD
authors.lastname: Hines
authors.forename: Thorsten A
authors.initials: TA
authors.lastname: Bley
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Lindstrom
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
mesh_terms: D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D055119:Elastic Modulus / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000033:anatomy & histology* / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity