Metabolic liver function in humans measured by 2-18F-fluoro-2-deoxy-D-galactose PET/CT–reproducibility and clinical potential

Abstract

Background: PET/CT with the radioactively labelled galactose analogue 2-18F-fluoro-2-deoxy-D-galactose (18F-FDGal) can be used to quantify the hepatic metabolic function and visualise regional metabolic heterogeneity. We determined the day-to-day variation in humans with and without liver disease. Furthermore, we examined whether the standardised uptake value (SUV) of 18F-FDGal from static scans can substitute the hepatic systemic clearance of 18F-FDGal (Kmet, mL blood/min/mL liver tissue/) quantified from dynamic scans as measure of metabolic function. Four patients with cirrhosis and six healthy subjects underwent two 18F-FDGal PET/CT scans within a median interval of 15 days for determination of day-to-day variation. The correlation between Kmet and SUV was examined using scan data and measured arterial blood concentrations of 18F-FDGal (blood samples) from 14 subjects from previous studies. Regional and whole-liver values of Kmet and SUV along with total metabolic liver volume and total metabolic liver function (total SUV, average SUV multiplied by total metabolic liver volume) were calculated. Results: No significant day-to-day differences were found for Kmet or SUV. SUV had higher intraclass correlation coefficients than Kmet (0.92–0.97 vs. 0.49–0.78). The relationship between Kmet and SUV was linear. Total metabolic liver volume had non-significant day-to-day variation (median difference 50 mL liver tissue; P = 0.6). Mean total SUV in healthy subjects was 23,840 (95% CI, 21,609; 26,070), significantly higher than in the patients (P < 0.001). Conclusions: The reproducibility of 18F-FDGal PET/CT was good and SUV can substitute Kmet for quantification of hepatic metabolic function. Total SUV of 18F-FDGal is a promising tool for quantification of metabolic liver function in pre-treatment evaluation of individual patients.