Abstract
389
Objectives The ability to non-invasively quantify beta cell mass (BCM) in the pancreas is valuable in the evaluation of the progression and treatment response in patients with Type-1 and Type-2 diabetes. This study examined the pharmacokinetics of a radiolabeled glucagon-like peptide (GLP-1) analog in PET imaging, to quantify the specific binding to GLP-1 receptor (GLP-1R) in a mini-pig model.
Methods Six male Ossabaw pigs (approximately 2-3 years old) were enrolled in a longitudinal study to monitor the progression of diabetes. All pigs underwent a 60 minute dynamic PET/CT scan of the abdomen on a Siemens 64-slice Biograph. Blood sampling was performed prior and throughout the PET acquisition. The PET uptake data was generated using CT-based ROIs for the connecting, duodenal, and splenic lobes of the pancreas. Pharmacokinetic modeling was performed using plasma input function and the kinetic analysis toolbox available on the Siemen’s Inveon Research Workplace 4.0 suite. The total distribution volume VT = (K1/k2)*(1+k3/k4) was estimated with reversible two-compartment model for each lobe of the pancreas.
Results The total volume of distribution VT was significantly higher in the duodenal lobe compared to the splenic lobe (p < 0.5) but not significantly higher than the connecting lobe. In the splenic and duodenal lobes, VT was inversely correlated with the volume of the lobe, indicative of higher islet density in the duodenal lobe. The SUV analysis also showed higher radioactivity concentration per volume for the duodenal lobe.
Conclusions The islet density in the human pancreas has been reported to be about 2-fold higher in the splenic than the duodenal lobe. In this study, we showed through pharmacokinetics modeling that islet density in the duodenal lobe is higher than the splenic lobe in the porcine pancreas.