Functional MR imaging during hypercapnia and hyperoxia: noninvasive tool for monitoring changes in liver perfusion and hemodynamics in a rat model.
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.
Barash
Hila
H
Goldyne Savad Institute for Gene Therapy, MRI/MRS Lab HBRC, Hadassah Hebrew University Medical Center, POB 12000, Jerusalem 91120, Israel.
Gross
Eitan
E
Matot
Idit
I
Edrei
Yifat
Y
Tsarfaty
Galia
G
Spira
Gadi
G
Vlodavsky
Israel
I
Galun
Eithan
E
Abramovitch
Rinat
R
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