title: Towards compression-sensitive magnetic resonance elastography of the liver: sensitivity of harmonic volumetric strain to portal hypertension.
abstract: OBJECTIVE
  To assess induced oscillating volumetric strain as a biomarker for intrahepatic blood pressure abnormalities.
  
  
  METHODS
  Harmonic vibrations of 25 and 50 Hz frequency were induced in the liver and measured by fast 3D vector field magnetic resonance elastography (MRE), followed by processing of the decomposed curl (shear) and divergence (compression) fields. After an initial study on an excised sheep liver, a group of 13 patients with hepatic hypertension were examined before and after implantation of a transjugular intrahepatic portosystemic shunt (TIPS).
  
  
  RESULTS
  In the sheep liver specimen, volumetric strain decreased with excess portal pressure, whereas shear strain was not sensitive to portal pressure. In the patient cohort, volumetric strain was significantly higher after TIPS placement (P = 1.38·10(-5) ), while neither shear strain nor the shear modulus were affected. Normalized changes in volumetric strain were significantly correlated with the hepatic venous pressure gradient (R(2) = 0.7258, P = 6.95·10(-5) ) and portal venous pressure (R(2) = 0.5028, P = 0.0016).
  
  
  CONCLUSIONS
  These results indicate for the first time the sensitivity of volumetric strain to symptomatically high values of tissue pressure and motivate further developments in compression-sensitive MRE and poroelastography towards image-based and noninvasive markers of tissue pressure.
authors: Department of Radiology, Charité, Universitätsmedizin Berlin, Berlin, Germany.
authors: Sebastian
authors: S
authors: Hirsch
authors: Jing
authors: J
authors: Guo
authors: Rolf
authors: R
authors: Reiter
authors: Eckart
authors: E
authors: Schott
authors: Carsten
authors: C
authors: Büning
authors: Rajan
authors: R
authors: Somasundaram
authors: Jürgen
authors: J
authors: Braun
authors: Ingolf
authors: I
authors: Sack
authors: Thomas J
authors: TJ
authors: Kroencke
mesh_terms: D000368:Aged; D000818:Animals; D019245:Compressive Strength; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods*; D006801:Humans; D006975:Hypertension, Portal / Q000473:pathology* / Q000503:physiopathology*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D066298:In Vitro Techniques; D008099:Liver / Q000473:pathology* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D033081:Shear Strength; D012756:Sheep; D013314:Stress, Mechanical
keywords: MRE; TIPS; compression modulus; divergence; liver; magnetic resonance elastography; portal hypertension; portosystemic shunt; pressure; pressure gradient; volumetric strain