title: Functional MR imaging during hypercapnia and hyperoxia: noninvasive tool for monitoring changes in liver perfusion and hemodynamics in a rat model.
abstract: OBJECTIVE
  To prospectively assess functional magnetic resonance (MR) imaging during hypercapnia and hyperoxia for monitoring changes in liver perfusion and hemodynamics in rats.
  
  
  METHODS
  All experiments were performed with approval of an animal care and use committee. Functional T2*-weighted gradient-echo MR images of the rat liver were acquired during hyperoxia and graded hypercapnia (n=24). Additional images were acquired during portal vein ligation (n=4), induced hypovolemia (n=5), and 70% hepatectomy (n=5). Hypercapnic effects were confirmed with Doppler ultrasonography and with gadopentetate dimeglumine. Differences between groups were analyzed by using Wilcoxon rank sum test, except for the graded hypercapnia, for which one-way analysis of variance was used.
  
  
  RESULTS
  Liver signal intensity (SI) increased due to hyperoxia; the percentage change in SI was seven times greater than that in muscle tissue; this reflects higher vascularity of the liver. Liver SI decreased due to hypercapnia; the percentage change in SI was negative in the liver but positive in the muscle (P<.001). Induced hypovolemia resulted in considerable decreases in functional MR imaging response; this reflects lower liver perfusion. Clinical applicability of the functional MR imaging method was proved by monitoring changes in liver perfusion that resulted from liver resection.
  
  
  CONCLUSIONS
  In the liver, the magnitude of the percentage change in SI induced by hypercapnia and hyperoxia reflects changes in total blood volume; whereas percentage change in SI values induced by hypercapnia from a negative to a positive value reflects relative changes in portal-to-arterial blood flow ratio.
authors.affiliation: Goldyne Savad Institute for Gene Therapy, MRI/MRS Lab HBRC, Hadassah Hebrew University Medical Center, POB 12000, Jerusalem 91120, Israel.
authors.forename: Hila
authors.initials: H
authors.lastname: Barash
authors.forename: Eitan
authors.initials: E
authors.lastname: Gross
authors.forename: Idit
authors.initials: I
authors.lastname: Matot
authors.forename: Yifat
authors.initials: Y
authors.lastname: Edrei
authors.forename: Galia
authors.initials: G
authors.lastname: Tsarfaty
authors.forename: Gadi
authors.initials: G
authors.lastname: Spira
authors.forename: Israel
authors.initials: I
authors.lastname: Vlodavsky
authors.forename: Eithan
authors.initials: E
authors.lastname: Galun
authors.forename: Rinat
authors.initials: R
authors.lastname: Abramovitch
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D004195:Disease Models, Animal; D006935:Hypercapnia / Q000150:complications / Q000175:diagnosis*; D018496:Hyperoxia / Q000150:complications / Q000175:diagnosis*; D008099:Liver / Q000098:blood supply / Q000473:pathology; D008102:Liver Circulation; D008107:Liver Diseases / Q000150:complications / Q000175:diagnosis*; D008111:Liver Function Tests / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity