Quantification of liver perfusion by positron emission tomography and H215O and relationship with glucose metabolism and substrate levels.

Background/Aims: Hepatic perfusion plays an important role in liver physiology and disease. This study was undertaken to (a) validate the use of Positron Emission Tomography (PET) and oxygen-15-labeled water ([15O]H2O) to quantify hepatic and portal perfusion, and (b) examine relationships between portal perfusion and liver glucose and lipid metabolism. Methods: Liver [15O]H2O-PET images were obtained in 14 pigs during fasting or hyperinsulinemia. Carotid arterial and portal venous blood were sampled for [15O]H2O activity; Doppler ultrasonography was used invasively as the reference method. A single arterial input compartment model was developed to estimate portal tracer kinetics and liver perfusion. Endogenous glucose production (EGP) and insulin-mediated whole body glucose uptake (wbGU) were determined by standard methods. Results: Hepatic arterial and portal venous perfusions were 0.15 ± 0.07 and 1.11 ± 0.34 ml/min/ml of tissue, respectively. The agreement between ultrasonography and [15O]H2O-PET was good for total and portal liver perfusion, and poor for arterial perfusion. Portal perfusion was correlated with EGP (r = +0.62, p = 0.03), triglyceride (r = +0.66, p = 0.01), free fatty acid levels (r = +0.76, p = 0.003), and plasma lactate levels (r = 0.81, p = 0.0009). Conclusions:Estimates of liver perfusion by [15O]H2O-PET compared well with those by ultrasonography. The method allowed to predict portal tracer concentrations which is essential in human studies. Portal perfusion may affect liver nutrient handling.