Use of Caval Subtraction 2D Phase-Contrast MR Imaging to Measure Total Liver and Hepatic Arterial Blood Flow: Preclinical Validation and Initial Clinical Translation

Purpose: To validate caval subtraction two-dimensional (2D) phasecontrast magnetic resonance (MR) imaging measurements of total liver blood flow (TLBF) and hepatic arterial fraction in an animal model and evaluate consistency and reproducibility in humans. Materials and Methods: Approval from the institutional ethical committee for animal care and research ethics was obtained. Fifteen Sprague-Dawley rats underwent 2D phase-contrast MR imaging of the portal vein (PV) and infrahepatic and suprahepatic inferior vena cava (IVC). TLBF and hepatic arterial flow were estimated by subtracting infrahepatic from suprahepatic IVC flow and PV flow from estimated TLBF, respectively. Direct PV transittime ultrasonography (US) and fluorescent microsphere measurements of hepatic arterial fraction were the standards of reference. Thereafter, consistency of caval subtraction phasecontrast MR imaging-derived TLBF and hepatic arterial flow was assessed in 13 volunteers (mean age, 28.3 years 6 1.4) against directly measured phase-contrast MR imaging PV and proper hepatic arterial inflow; reproducibility was measured after 7 days. Bland-Altman analysis of agreement and coefficient of variation comparisons were undertaken. Results: There was good agreement between PV flow measured with phase-contrast MR imaging and that measured with transittime US (mean difference, 23.5 mL/min/100 g; 95% limits of agreement [LOA], 661.3 mL/min/100 g). Hepatic arterial fraction obtained with caval subtraction agreed well with those with fluorescent microspheres (mean difference, 4.2%; 95% LOA, 620.5%). Good consistency was demonstrated between TLBF in humans measured with caval subtraction and direct inflow phase-contrast MR imaging (mean difference, 21.3 mL/min/100 g; 95% LOA, 623.1 mL/min/100 g). TLBF reproducibility at 7 days was similar between the two methods (95% LOA, 631.6 mL/min/100 g vs 629.6 mL/min/100 g). Conclusion: Caval subtraction phase-contrast MR imaging is a simple and clinically viable method for measuring TLBF and hepatic arterial flow. Published under a CC BY 4.0 license.