Using MRI to study the alterations in liver blood flow, perfusion, and oxygenation in response to physiological stress challenges: Meal, hyperoxia, and hypercapnia

Abstract

Background: Noninvasive assessment of dynamic changes in liver blood flow, perfusion, and oxygenation using MRI may allow detection of subtle hemodynamic alterations in cirrhosis. Purpose: To assess the feasibility of measuring dynamic liver blood flow, perfusion, and T 2 * alterations in response to meal, hypercapnia, and hyperoxia challenges. Study Type: Prospective. Subjects: Ten healthy volunteers (HV) and 10 patients with compensated cirrhosis (CC). Field Strength/Sequence: 3T; phase contrast, arterial spin labeling, and (Formula presented.) mapping. Assessment: Dynamic changes in portal vein and hepatic artery blood flow (using phase contrast MRI), liver perfusion (using arterial spin labeling), and blood oxygenation ((Formula presented.) mapping) following a meal challenge (660 kcal), hyperoxia (target P ET O 2 of 500 mmHg), and hypercapnia (target increase P ET CO 2 of ∼6 mmHg). Statistical Tests: Tests between baseline and each challenge were performed using a paired two-tailed t-test (parametric) or Wilcoxon-signed-ranks test (nonparametric). Repeatability and reproducibility were determined by the coefficient of variation (CoV). Results: Portal vein velocity increased following the meal (70 ± 9%, P < 0.001) and hypercapnic (7 (5–11)%, P = 0.029) challenge, while hepatic artery flow decreased (–30 ± 18%, P = 0.005) following the meal challenge in HV. In CC patients, portal vein velocity increased (37 ± 13%, P = 0.012) without the decrease in hepatic artery flow following the meal. In both groups, the meal increased liver perfusion (HV: 82 ± 50%, P < 0.0001; CC: 27 (16–42)%, P = 0.011) with faster arrival time of blood (HV: –54 (–56-30)%, P = 0.074; CC: –42 ± 32%, P = 0.005). In HVs, T *2 increased after the meal and in response to hyperoxia, with a decrease in hypercapnia (6 ± 8% P = 0.052; 3 ± 5%, P = 0.075; –5 ± 6%, P = 0.073, respectively), but no change in CC patients. Baseline between-session CoV <15% for blood flow and <10% for T *2 measures. Data Conclusion: Dynamic changes in liver perfusion, blood flow, and oxygenation following a meal, hyperoxic, and hypercapnic challenges can be measured using noninvasive MRI and potentially be used to stratify patients with cirrhosis. Level of Evidence: 2. Technical Efficacy: Stage 1. J. Magn. Reson. Imaging 2019;49:1577–1586.