title: Whole-organ and segmental stiffness measured with liver magnetic resonance elastography in healthy adults: significance of the region of interest.
abstract: OBJECTIVE
  MR elastography (MRE) is a recent non-invasive technique that provides in vivo data on the viscoelasticity of the liver. Since the method is not well established, several different protocols were proposed that differ in results. The aim of the study was to analyze the variability of stiffness measurements in different regions of the liver.
  
  
  METHODS
  Twenty healthy adults aged 24-45 years were recruited. The examination was performed using a mechanical excitation of 64 Hz. MRE images were fused with axial T2WI breath-hold images (thickness 10 mm, spacing 10 mm). Stiffness was measured as a mean value of each cross section of the whole liver, on a single largest cross section, in the right lobe, and in ROIs (50 pix.) placed in the center of the left lobe, segments 5/6, 7, 8, and the parahilar region.
  
  
  RESULTS
  Whole-liver stiffness ranged from 1.56 to 2.75 kPa. Mean segmental stiffness differed significantly between the tested regions (range from 1.55 ± 0.28 to 2.37 ± 0.32 kPa; P < 0.0001, ANOVA). Within-method variability of measurements ranged from 14 % for whole liver and segment 8-26 % for segment 7. Within-subject variability ranged from 13 to 31 %. Results of measurement within segment 8 were closest to the whole-liver method (ICC, 0.84).
  
  
  CONCLUSIONS
  Stiffness of the liver presented significant variability depending on the region of measurement. The most reproducible method is averaging of cross sections of the whole liver. There was significant variability between stiffness in subjects considered healthy, which requires further investigation.
authors.affiliation: Department of Radiology and Diagnostic Imaging, Nicolaus Copernicus University, Collegium Medicum, ul. Skłodowskiej-Curie 9, 85-094, Bydgoszcz, Poland.
authors.forename: Grażyna
authors.initials: G
authors.lastname: Rusak
authors.forename: Elżbieta
authors.initials: E
authors.lastname: Zawada
authors.forename: Adam
authors.initials: A
authors.lastname: Lemanowicz
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Serafin
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D054459:Elasticity Imaging Techniques; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008099:Liver / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D055815:Young Adult