Hepatic Blood Perfusion Measured by 3-Minute Dynamic ¹⁸F-FDG PET in Pigs

Abstract

There is an unmet clinical need for an imaging method for quantification of hepatic blood perfusion. The purpose of the present study was to develop and validate a PET method using blood-to-cell clearance (K₁) of ¹⁸F-FDG, 3-O-¹¹C-methylglucose (¹¹C-MG), or 2-¹⁸F-fluoro-2-deoxy-D-galactose (¹⁸F-FDGal) as a measure of hepatic blood perfusion without the need for portal venous blood samples. We aimed to make the method as simple as possible with the prospect of future application to clinical studies. For this purpose, we examined the possibility of using a 3-min data acquisition and a model-derived dual input calculated from measurements of radioactivity concentrations in a peripheral artery. Methods: Pigs (40 kg) underwent dynamic PET of the liver with ¹⁸F-FDG, ¹¹C-MG, or ¹⁸F-FDGal with simultaneous measurements of time–activity curves in blood sampled from a femoral artery and the portal vein (PV); blood flow rates were measured in the hepatic artery (HA) and PV by transit-time flow meters. Two input functions were compared: A measured dual input and a model-derived dual input, the latter with the PV time–activity curve estimated from the measured arterial time–activity curve and a previously validated 1-parametric PV model. K₁ was estimated for each tracer by fitting compartmental models to the data, comparing 3-min and 60-min data acquisitions and the 2 dual-input time–activity curves. Results: Agreement between K₁ estimated using the measured and the model-derived dual input was good for all 3 tracers. For ¹⁸F-FDG and ¹¹C-MG, K₁ (3-min data acquisition, model-derived dual input, and 1-tissue compartmental model) correlated to the measured blood perfusion (P = 0.01 and P = 0.07, respectively). For ¹⁸F-FDGal, the correlation was not significant. Conclusion: A simplified method for quantification of hepatic blood perfusion using 3-min dynamic ¹⁸F-FDG PET or ¹¹C-MG PET with blood sampling from only a peripheral artery was developed. Parametric K₁ images were constructed and showed homogeneous blood perfusion in these normal livers.