Cross-sectional and Test-Retest Characterization of PET with [18F]FP-(+)-DTBZ for ? Cell Mass Estimates in Diabetes

Purpose: The vesicular monoamine transporter, type 2 (VMAT2) is expressed by insulin producing ? cells and was evaluated as a biomarker of ? cell mass (BCM) by positron emission tomography (PET) with [¹⁸F]fluoropropyl-dihydrotetrabenazine ([¹⁸F]FP-(+)-DTBZ). Procedures: We evaluated the feasibility of longitudinal pancreatic PET VMAT2 quantification in the pancreas in two studies of healthy controls and patients with type 1 or 2 diabetes. VMAT2 binding potential (BP<inf>ND</inf>) was estimated voxelwise using a reference tissue method in a cross-sectional study, followed by assessment of reproducibility using a test-retest paradigm. Metabolic function was evaluated by stimulated c-peptide measurements. Results: Pancreatic BP<inf>ND</inf> was significantly decreased in patients with type 1 diabetes relative to controls and the test-retest variability was 9.4 %. Conclusions: Pancreatic VMAT2 content is significantly reduced in long-term diabetes patients relative to controls and repeat scans are sufficiently reproducible to suggest the feasibility clinically VMAT2 measurements in longitudinal studies of new onset diabetes.