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

PURPOSE: The vesicular monoamine transporter, type 2 (VMAT2) is expressed by insulin producing β cells and was evaluated as a biomarker of β cell mass (BCM) by positron emission tomography (PET) with [(18)F]fluoropropyl-dihydrotetrabenazine ([(18)F]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(ND)) 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(ND) 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. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11307-015-0888-7) contains supplementary material, which is available to authorized users.