Pancreatic perfusion and its response to glucose as measured by simultaneous PET/MRI

Aims Perfusion of the pancreas and the islets of Langerhans is sensitive to physiological stimuli and is dysregulated in metabolic disease. Pancreatic perfusion can be assessed by both positron emission tomography (PET) and magnetic resonance imaging (MRI), but the methods have not been directly compared or benchmarked against the gold-standard microsphere technique. Methods Pigs (n = 4) were examined by [O-15]H2O PET and intravoxel incoherent motion (IVIM) MRI technique simultaneously using a hybrid PET/MRI scanner. The pancreatic perfusion was measured both at basal conditions and after intravenous (IV) administration of up to 0.5 g/kg glucose. Results Pancreatic perfusion increased by 35%, 157%, and 29% after IV 0.5 g/kg glucose compared to during basal conditions, as assessed by [O-15]H2O PET, IVIM MRI, and microspheres, respectively. There was a correlation between pancreatic perfusion as assessed by [O-15]H2O PET and IVIM MRI (r = 0.81, R-2 = 0.65, p < 0.01). The absolute quantification of pancreatic perfusion (ml/min/g) by [O-15]H2O PET was within a 15% error of margin of the microsphere technique. Conclusion Pancreatic perfusion by [O-15]H2O PET was in agreement with the microsphere technique assessment. The IVIM MRI method has the potential to replace [O-15]H2O PET if the pancreatic perfusion is sufficiently large, but not when absolute quantitation is required.