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Published online before print April 26, 2007, 10.1148/radiol.2433060433
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(Radiology 2007;243:727-735.)
© RSNA, 2007

Experimental Studies

Functional MR Imaging during Hypercapnia and Hyperoxia: Noninvasive Tool for Monitoring Changes in Liver Perfusion and Hemodynamics in a Rat Model1

Hila Barash, MSc, Eitan Gross, MD, Idit Matot, MD, Yifat Edrei, BSc, Galia Tsarfaty, MD, Gadi Spira, PhD, Israel Vlodavsky, PhD, Eithan Galun, MD, and Rinat Abramovitch, PhD

1 From the Goldyne Savad Institute for Gene Therapy (H.B., Y.E., E. Galun, R.A.), MRI/MRS Lab HBRC (H.B., Y.E., R.A.), Department of Pediatric Surgery (E. Gross), and Department of Anesthesiology and Critical Care Medicine (I.M.), Hadassah Hebrew University Medical Center, POB 12000, Jerusalem 91120, Israel; Department of Radiology, Sheba Medical Center, Tel Hashomer, Israel (G.T.); and Department of Anatomy and Cell Biology (G.S.) and Cancer and Vascular Biology Research Center (I.V.), Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel. Received March 9, 2006; revision requested May 8; revision received June 27; accepted July 21; final version accepted October 2. Supported in part by Philip Morris USA and Philip Morris International (R.A.), by the Yeshya Horowitz Association through the Center for Complexity Science (R.A., H.B.), by the Belfer Foundation (R.A.), by a grant from the Israeli Ministry of Science (E. Galun), and by the Yeshya Horowitz Foundation. Address correspondence to R.A. (e-mail: rinat{at}hadassah.org.il).

Purpose: To prospectively assess functional magnetic resonance (MR) imaging during hypercapnia and hyperoxia for monitoring changes in liver perfusion and hemodynamics in rats.

Materials and 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.

Conclusion: 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.

Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/2433060433/DC1

© RSNA, 2007